Chepter Wise Questions

7/27/2019 Chepter Wise Questions

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(b) CsCl coordination number is 8. It is surrounded by 8 anion tightly.

Q. 4. How many unit cells are present in a cube shaped ideal crystal of NaCl of mass 1gm ?

Ans. Mass of 1 unit cell = volume density

= a d

=3

0 3

a M ZN a

= 2358.5 4

6.023 10

No. of unit cells in 1 gm = 1/M

= 6.023 1023

/ 58.5 4= 2.57 1021

Q. 5. In the mineral spinal; having the formula MgAl2O4. The oxide ions are arrangedin CCP, Mg2+ ions occupy the tetrahedral voids. While Al3+ ions occupy theoctahedral voids.

(i) What percentage of tetrahedral voids is occupied by Mg2+ ions ?

(ii) What percentage of octahedral voids is occupied by Al3+ ions ?Ans. According to the formula, MgAl2O4. If there are 4 oxide ions, there will be 1 Mg2+

ions and 2 Al3+. But if the 4 O2 ions are ccp in arrangement, there will be 4 octahedraland 8 tetrahedral voids.

(i) Percentage of tetrahedral voids occupied by Mg2+ = (1 / 8) 100

= 12.5%

(ii) Percentage of octahedral voids occupied by Al3+ = (2 / 4) 100

= 50%

Q. 6. Give reasons :(a) Window glass of old building look milky.

b) Window glass of old building is thick at bottom.(c) CaCl2 will introduce Schottky defect if added to AgCl crystal.

Ans. (a) Due to annealing over a number of years glass acquires some crystallincharacter.

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(b) Glass is not a true solid. But a super-cooled liquid of high viscosity. It has th property to flow.

(c) 2 Ag+ will be replaced by 1 Ca2+ ions to maintain electrical neutrality. Thus ahole is created and lattice site for every Ca2+ ion introduced.

Q. 7. Analysis shows that nickel oxide has the formula NiO.98O1.00. What fractions of nickel exist as Ni2+ and Ni3+ ions ?

Ans. NiO.98O1.00

Let Ni2+ be x and Ni3+ be 0.98 x

Total charge on compd. is equal to zero.

[2 (Ni2+) + 3 (Ni3+) 2 (O2 )] = 0

2 x + 3 (0.98 x) 2 = 0x = 0.94

Therefore Ni2+ % =0.940.98

100 = 96%

Ni3+ = 4%

Q. 8. What type of defect can arise when a solid is heated ? Which physical property isaffected by this and in what way ?

Ans. When a solid is heated vacancy defect arises. This is because on heating some atomor ions leacve the lattice site completely some lattice sites are vacant. As a result this defect the density of the substance decreases, because some atoms leave thstructure completely.

Q. 9. (a) What happens when a Ferromagnetic or Ferrimagnetic solid is heated ?

(b) The ions of MgO and NaF all have the same number of electrons andintermolecular distance are about the same (235 & 215 pm). Why are themelting points are so different (2642 C & 992 C ?

Ans. (a) It changes into paramagnetic at hight temperature due to randomization ospins.

(b) The ions in MgO carry two unit charges. In NaCl only one unit charge. Henelectrostatic forces of attraction in MgO are stronger.

Q. 10. (a) If the radius of the Br ion is 0.182 nm, how large a cation can fit in each of the tetrahedral hole.

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(b) AgI crystallizes in a cubic closed packed ZnS structure. What fraction of tetrahedral site is occupied by Ag ion ?

(c) At what temp. range, most of the metals becomes super conductors ?

Ans. (a) For a tetrahedron the limiting ratio is 0.225 0.414

For largest cation highest value 0.414 would be considered.

r + / r = 0.414

r + = 0.414 0.182 = 0.075 nm.

(b) In FCC there are 8 tetrahedral voids. Out of this is occupied by Ag cation.

(c) 2 k 5 k.

Q1.Examine the illustration of a portion of the defective crystal given below and answer tfollowing questions:

(i) What are these type of vacancy defect called?

(ii) How is the density of a crystal affected by these defects?

(iii) Name one ionic compound which can show this type of defect in the crystalline state.

(iv) How is the stoichiometry of the compound affected?(2 marks)

Q2.Analysis shows that a metal oxide has the empirical formula M0.96O1.00. Calculate the percentage of M2+ and M3+ ions in this crystal.(2 marks)

Q3.In an ionic compound the anion (N-) forms cubic close packing, while the cation (M+)occupy one third of the tetrahedral voids.

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Deduce the empirical formula of the compound and the coordination number of (M+) ions.(2marks)

Q4.The radius of copper atom is 118 pm. If copper crystallizes in a face-centered cubiclattice, what is the size of the unit cell?(2 marks)

Q5.Why are amorphous solids to be considered as supercooled liquids?(2 marks)

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Q1. What is meant by the term Co-ordination no?Ans:- No of atoms (sphere) by which the central atom is surrounded.

Q2. What is the co-ordination no of atoms:-(a) In a cubic close packet structure -12(b) In a body centred cubic structure:-8

Q3. A cubic solid is made of two elements P and Q. Atoms of Q are at the corner of thecube and P at the body centre. What is the formula of the compound? What are the co-ordination No. of P and Q.

Ans:-PQ

Q5. Analysis shows that nickel oxide has the formula Ni0.98as I1.00. What fraction of Niexit as Ni2+and Ni3+ ions?

Ans:- Let the no of Ni2+ ion = X Ni3+ion = 0.98 X

As per the question2 X + 3(0.98- X) = 22 X + 3 X 0.98 -3 X =22 X 3 X = 2 - 3 X 0.98=2-2.94X = 0.94X =94So fraction of Ni2+= 94%And Ni3+= 06%

Q4. What is difference between Frenkel and schottky defect? (any two)Ans:-

Frenkel defect Schottky defect(a) In this defect shifting of iconfrom its position to interstitial site.

(a) In this defect there is missing of equalno of cation and anion.

(b) Density remain same. (b)Density decreases.

Q5. Silver Crystallises in fcc lattice. If edge length of the cell is 4.077 X 10-8 cmanddensity is 10.5 g cm-3. Calculate the atomic mass of silver.

Ans:- density =10.5 gm/cm3, Z=4

We Know

gm

x x x x M

x x x xM

xa N zxM

d

14.1074

10)077.4(5.1010022.6

)10077.4(10022.64

24323

382330

=

=

==

Hence atomic mass of silver=107.14 gm.

Q6. Classify each of the following as being either a p-type or an n-type Semiconductor.(a) Ge dopped with In----p-type.(b) B dopped with Si----n-type.

Q7. Zinc oxide is white but it turns yellow on heating. Explain?Ans:- When Zinc oxide is heated it loses oxygen.

ZnO-------- Zn2+

+ 1/2 O2

+ 2e-

Zn2+ adopt the interstitial void and electron in the neighbouring voids. Due to presence of electron in void, the colour is yellow.

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4. What makes the crystal of KCl appear some time violet?

5. What is the effect of Schottky and Frenkel defects on the density of crystalline solid

6. Name a substance which on addition to AgCl causes cation vacancy in it.

7. What happens when ferromagnetic Fe3O4 is heated at 850 K and why?

8. What is curie temperature?9. What is ferromagnetism different from paramagnetism?

10. What structural changes will occur if NaCl crystal is subjected to high pressure?

FOR AVERAGE1. An element (at. Mass=60) having fcc structure has a density of 6.23 g cm-3. What is

the edge length of the unit cell? (Avg. const. N = 6.02 x 1023mol-1)

2. The density of CsBr, which has a BCC structure, is 4.4 g cm-3. The edge length of theunit cell is 400 pm. Calculate the interionic distance in crystal of CsBr (NA= 6.0231023, At. Mass of Cs= 133, Br= 80)

3. The composition of a sample wustite is Fe0.93 O1.00, what percentage of the iron present in the form of Fe(III)?

4. NaCl crystallizes in FCC structure. Its density is 2.165 gm cm-3. If the distance between Na+ and its nearest Cl- is 281 pm. Find out the Avog. No. (Na=23 g mol-1, Cl= 35.5 g mol-1)

5. The compound CuCl has ZnS structure and the edge length of its unit cell is 500 Calculate the density. (At. Mass, Cu=63, Cl=35.5, NA=6.02 x 1023)

FOR BELOW AVERAGE02 or 03 Marks Questions1. Calculate the efficiency of packing in a case of metal crystals for simple cube or bo

centered cube or face centered cube (with the assumption that atoms are touchineach other)

2. How can you determine the atomic mass of an unknown metal if you know idensity and the dimension of its unit cell? Explain.

3. If the radius of the octahedral void isr and radius of the atoms in close packing is R.derive relationship betweenr and R.

4. Explain the following with suitable examples:(a) Ferromagnetism (b) Paramagnetism (c) Ferrimagnetism

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(d) Anti ferromagnetism (e) 12-16 groups (f) 13-15 groups

(g) Schottky defect (h) Frenkel defect (i) F-centre

(j) Doping (k) n-type semiconductor (l) p-type semiconductor

(m) Conductor/ Insulator/ Semiconductors.

NUMERICAL PROBLEMS1. If NaCl is doped with 10-3 mol%. What is the concentration of cation vacancies?

2. Aluminum crystallizes in a cubic close packed structure. Its metallic radius is 125p(a) what is the edge length of unit cell? (b) How many unit cells are there in 1.00 c3

of aluminum?

3. Silver formsccp lattice and x-ray studies of its crystal show that edge length of itsunit cell is 408.6pm. Calculate the density of silver (Atomic mass = 107.9 u)

4. Niobium crystallizes in body centre cubic structure. If density is 8.55 gm/cCalculate atomic radius of niobium using its atomic mass 93.

5. Silver crystallizes in face lattice. If edge length of the cell in 4.07 x 10-8 cm andensity is 10.5 gm/cc. Calculate the atomic mass of silver.

6. Gold (atomic radius = 0.144 nm) crystallizes in a fcc unit cell. What is the length of aside of the cell?

7. An element (Atomic mass = 60) having fcc structure has a cell edge of 400 pm. Whatis its density? NA = 6.023 x 1023.

FOR ABOVE AVERAGE1. Analysis shows that nikel oxide has the formula Ni.98O1.00. What fraction of nic

exists as Ni+2and Ni+3 ions?

2. An element (atomic mass = 60) having face centred cubic unit cell has a density 6.23 gm/cc. what is edge length of unit cell?3. Metallic gold crystallizes in a fcc structure and has a density of 19.3 gm/cc. Calculate

the radius of gold atom. [atomic mass of Au=197, NA= 6.023 x 1023]4. Unit cell of an element (Atomic mass = 108 and density 10.5 gm/cc) has an ed

length 409 pm. Deduce the type of crystal lattice.5. An element has a body centred cubic structure with a cell edge of 288 pm. Th

density of the element in 7.2 gm/cc. How many atoms are present in 208 gm of thelements?

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STUDY MATERIAL

1. Solution : Homogeneous mixture of two or more pure substances.

2. Types of solutions :

a) Solid in solid solution. Eg: Bronze, Brass.

b) Liquid in solid solution. Eg: Zinc-amalgam.

c) Gas in solid solution. Eg: Solution of hydrogen in palladium.

d) Solid in liquid solution. Eg: Aqueous Sodium Chloride sol.

e) Liquid in liquid solution. Eg: Ethanol dissolved in water.

f) Gas in liquid solution. Eg: Carbondioxide dissolved in water, ammonia dissolved water.

g) Solid in gas solution. Eg: Iodine vapour in nitrogen .

h) Liquid in gas solution. Eg: Water vapoursin air, Chloroform vapour in nitrogen.

i) Gas in gas solution. Eg: Water gas, Producer gas.

3. Concentrations of solution :

a) Mole fraction ( X):

Xsolvent= nsolvent/nsolvent+ nsoluteXsolute= nsolute/nsolvent+ nsolute

b) Normality (N) :

N = WB/EB x 1000/V

c) Molarity (M) :M = WB/MB x 1000/Vd) Molality (m) :

m = WB/MB x 1000/WAWB = Mass of solute in gram.WA = Mass of solvent in gram.MB = Molar mass of solute.V = Volume of the solution.EB = Equivalent weight of the solution.

4. Henerys Law : Mass of gas dissolved per unit volume of the solvent is directly proportional to the pressure of the gas in equilibrium with the solution.

Limitations : Not applicable when pressure is very high.11

UNIT:-2SOLUTION


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Not applicable when the temperature is too low.Not applicable when the gas is highly soluble.

Not applicable when the gas react chemically with solvent and dissociate and associatethe solvent.

5. Colligative Properties : Properties of solution which depends upon the number of solute particles dissolved in it. Eg: R.L.V.P, Osmotic pressure, Elevation of boiling point.

6. Vapour Pressure : Pressure exerted by vapours in equilibrium with its liquids at agiven temperature.

7. Lowering of vapour Pressure :

P = PA0 P (PA0 = v.p of pure solvent, p = v.p of sol.)8. Relative lowering of vapour pressure : Ratio of lowering of vapour pressure of pu

solvent.

R.L.V.P = (PA0 P)/ PA0

9. Raults Law :a) Partial pressures of components in thesolutions are directly proportional to their mole fractions.b) R.L.V.P. of solution containing non volatile solute is equal to mole fraction of the

solute.10. Limitations of Raults Law;a) Applicable only to dilute solution. b) Applicable only to homogeneous solution.c) Applicable to the solution in which solute doesnot undergo association or dissociatio11. Boiling Point : Temperature at which vapour pressure of the liquid is equal to

atmos[heric pressure.12. Elevation of boiling Point : T b = T0 T = k b x m.Here T0and T are Boiling points of pure solvent and solution.m = molality , k b = Ebullioscopic constant.1. Freezing points : Temperature at which liquids and its solid phase have same vapo

pressure.

2. Depression of freezing point :

Tf = T - T0 = kf x m.

Here T0and T are freezing points of pure solvent and solutionm = molality , kf = Cryoscopic constant.3. Osmotic pressure : External pressure applied to the solution to just prevent osmos

4. Osmosis : Spontaneous flow of solvent molecule from lower concentrated solutioto higher concentrated solution through semi permeable membrane.

5. Reverse Osmosis : When the applied pressure is greater than osmosis pressure, thereverse osmosis take place. (used in desalination plants to meet potable water)

6. Isotonic solution : The solutions having same osmotic pressure.

7. Azeotropic mixture : Binary mixture of liquids having same composition in liquidand vapour phase and boils at the constant temperature.

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a) Maximum Boiling Azeotropes : Azeotropes boils at the temperature higher than th boiling point of its components. Eg: Mixture of HNO3 (68 %) and water (32%)

b) Minimum Boiling Azeotropes : Azeotropes boils at the temperature lower than th boiling point of its components. Eg: Mixture of Ethanol (95%) and water .

8. Ideal Solutions: Solutions obeying Raults Law and solvent solute molecular

forces are same as that of solvent solvent and solute solute molecular forces.Eg: Solution of N- Hexane and N- Heptane, Solution of Benzene and Toluene etc.

9. Positive Deviation from Raults Law : Solutions having solvent solute moleculaforces are weaker than that of solvent solvent of solute solute molecular forces

Hmix = + ve, Vmix= +ve and P > PA + PB .Eg: solution of ethanol and acetone, solution of carbondisulphide and acetone.10. Negative Deviation from Raults Law : Solutions having solvent solute molecul

forces are stronger than that of solvent solvent or solute solute molecular forc

Hmix = - ve, Vmix= - ve and P < PA + PB

11. Abnormal molecular mass : Molecular mass calculated by measurement of colligative properties differ from normal value due to association or dissociation osolutes in solution.

Modified equation for colligative properties are

a) P/ PA0 = i XB

b) T b = i k b x m.c) Tf = i kf x m.

d) = i C R T.

12. Vanthoff factor :

i = Mnormal/ Mobserved

ratio of observed value of colligative properties and normal value of colligative properis called vanthoff factor.

13. Degree of dissociation () = (i -1) / (n-1).

n = no. of particles formed from dissociation of 1 molecule.

i = vant hoff factor.14. Degree of association () = (i -1) / (1/n-1).

n = no. of simple molecule to form an associated molecule.

15. a) i >1 (solute undergoes dissociation).

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Important Questions:1. Define the Mole Fraction of a substances in a solution. What is sum of mole

fraction of all components in a three component system?

2. How is the molality of a solution different from its molarity?

3. Calculate the density of H2SO4 solution if molality and molarity are 94.5 and 11.5respectively.

4. How many ml of 0.1 (M) HCl required to react completely with a 1 gm mixture sodium carbonate and sodium bicarbonate containing equimolar amount of both.

5. State Henerys Law for a solubility of a gas in a liquid. Give its applications(three) and limitations?

6. Explain the significance of Henerys Law constant K H . At the same temperaturehydrogen is more soluble in water than Helium. Which of them will have a highevalue of K H and Why?

7. What concentration of nitrogen should be present in a glass of water at roomtemperature? Assume a temperature of 250 celcius. A total pressure of 1 atm andmole fraction of nitrogen in air is 0,78 (K H for nitrogen is 8.42 x 10-7M/mm Hg).

8. Henerys Law constant for CO2 in water is 1.67 x 108Pa at 298 K. calculate thequantity of CO2 in 500 ml of soda water when packed under 2.5 atm CO2 pressureat 298 K.

9. Mention some limitations of Raults Law.

10. Urea form ideal solution of water. Determine the vapour pressure an aqueoussolution containing 10 % by mass of urea at 400 C. (V.P of water at 400 C = 55.3mm Hg.).

11. Derive the equation to express the relative lowering of vapour pressure for asolution is equal to its mole fraction of the solute in it when the solvent alone isvolatile.

12. Two liquids X and Y boil at 1100 C and 1300 C, which one of them has higher vapour pressure at 500C.

13. Benzene and Toluene forms ideal solution over entire range of composition. Thevapour pressure of pure Benzene and Toluene at 300 K are 50.71 mm Hg and32.06 mm Hg respectively. Calculate the mole fraction of Benzene in vapour phase if 80 gm of Benzene is mixed with 100 gm Toluene.

14. An aquous solution of 2 % non volatile solute exerts a pressure of 1.004 bar anormal boiling point of solvent. What will be the molar mass of solute. (V.P of pure water = 1.013 bar).

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15. A person suffering from high blood pressure is advised to take minimum quantiof salt.

16. Write the name of two inorganic substance (compounds) which can be used assemipermiable membrane.

17. 100 mg protein is dissolved in enough water to make 10 ml of solution if this

solution has an osmotic pressure of 33.3 mm Hg at 250

C . what is the molar massof protein. ( R = 0.0821 L atm mol-1 K -1 and 760 mmHg = 1 atm).

18. State condition resulting in reverse osmosis. Give one of its application.

19. Define the following with a suitable example :

a) Maximum and minimum boiling azeotropes.

b) Desalination

c) Ideal solution

d) Abnormal molecular mass

20. a) Define Vanthoff factor.

b) What is the Vanthoff factor for a compound which

undergoes tetramerisation in an organic solvent.

c) What would be the value of Vanthoff factor for

1) dilute solution of K 2SO4 in water 2) Na2SO4.10H2O in water

3) Ethanoic acid in Benzene

d) When is the value of Vanthoff factor

1) more than one

2) less than one

3) equal to oneHints:3. m = 1000 M / (1000d MMB) ,

M=molarity, MB = molar mass of solute, d= density of sol.d = 1.24 gm/cm3

4. 157.8 ml7. Partial pressure of nitrogen in atmosphere (P N2) = Ptotalx X N2

P N2= 592.8 mm HgSolubility of N2 = K Hx P N2= 4.99 x 10-4 (M)

8. K H = 1.67 x 108 Pa , PCO2= 2.5 atm = 2.5 x 1.01325 x 10-5 PaPCO2 = K H x XCO2, XCO2 = 1.517 x 10-3

nCO2/(nCO2+ nH2O) = 1.517 x 10-3nCO2= 42.14 x 10-3 mole.

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10. From Raults Law : (PA0 P)/PA0 = XB = nB/nAP = 53.46 mm Hg.

12. X has higher vapour pressure than Y.13. n benzene= 80/78 = 1.026 moles

ntoluene= 100/92 = 1.087 molesX benzene= 0.486 , Xtoluene= 0.514From Raults Law : PBen= PBen0 x XBen= 24.65 mm Hg

PTol= PTol0 x XTol = 16.48 mm HgMole fraction of Benzene in vapour phase =

PBen/PBen+ PTol = 0.60.14. (PA0 P)/PA0 = XB = nB/nA

MB = 41.34 gm mol-116. Calcium phosphate , Copper Ferrocyanide

17. = C x R x T

= WB x R x T/MBVMB = 13980.45 gm Mol-1

18. External pressure greater than osmotic pressureDesalination plant .20. a) Ratio of observed value of colligative properties to the

normal value of colligative properties is called Vanthoff factor. b) i = c) 1) 3,

2) 3,3)

d) 1) solute undergoes dissociation in the solution2) solute undergoes association in the solution

3) solute undergoes neither dissociation nor association

1 MARK QUESTIONSQ. 1.The vapour pressure of deliquescent substance is less or more than that of watervapours in air ?Ans. Less than that of water vapours in air.Q. 2. If is the degree of dissociation of Na2SO4then write the Vant Hoff factor usedfor calculating the molecular mass.Ans. = i 1 / m 1, => (m 1) = i 1, => 1 + (m 1) = i, => i = 1 + (3 1),

=> i = 1 + 2 .Q. 3. If 6.023 1020molecules of urea are present in 10 ml of its soln. then what is theconc. of urea soln.?Ans. N0= 6.023 1023 = 1 mol

6.023 1020molecules = 0.001 mol in 10 mlM =

N 1000

v

=

.001 1000

10 1000

= 0.01 M.

Q. 4.Why camphor is used in molecular mass determination ?Ans. Because it has very high cryoscopic constant.

It has large depression in m. p. when an organic solute is dissolved in it.Q. 5.0.004 M soln of Na2SO4is isotonic with 0.01 M soln of glucose at the temp. What isthe apparent degree of dissociation of Na2SO4?

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Ans. 75%Q. 6.What happen when mango is placed in dilute aqueous soln. of HCl?Ans. When mango is placed in dilute aqueous soln. of HCl it swells.Q. 7. Out of (a) 200 ml of 2 M NaCl Soln. and (b) 200 ml of 1 M glucose Soln. which onehas higher osmotic pressure?Ans.: (a) 200 ml of 2 M NaCl Soln. NaCl is an electrolyte which dissolve to give ions. Glucose and urea are non electrolytes.Thus glucose has minimum conc. and hence minimum osmotic pressure.Q. 8.Out of (a) 0.01 M KNO3, (b) 0.01 M Na2SO4which aqueous soln. will exhibit highB. P.?Ans. (a) 0.01 M Na2SO4Q. 9.Out of (a) 1 M CaCl2(b) 1 M AlCl3which aqueous soln. will show max. vapourpressure at 300 K ?Ans. (a) 1 M CaCl3, if we assume 100% dissociation, i for CaCl2= 3 and AlCl3= 4 andrelative lowering of V. P. is directly proportional to i.Q. 10. Out of (a) HNO3+ H2O and (b) C6H6+ C6H5CH3which will form max. boilingazeotrope ?Ans. (a) HNO3+ H2O.

2 MARKS QUESTIONSQ. 1.Two solns of a substance (non-electrolyte) are mixed in the following manner 480ml of 1.5 M (First Soln) + 520 ml of 1.2 M (Second Soln). What is the molarity of thefinal mixture ?

Ans. Total molarity =1 1 2 21 2

M V M VV V

++ =

1.5 480 1.2 520

480 520

+

+=1.344 M

Q. 2.To get the hard boiled eggs, why common salt is added to water before boiling theeggs?Ans. Due to addition of common salt the B. P. of the salt containing water elevated, hencthe egg at high temperature becomes hard.Q. 3.Equimolar Soln. of NaCl and BaCl2are prepared in H2O. D. F. pt. of NaCl isfound to be 2 C. What freezing point do you expect from BaCl2soln ?Ans. i for NaCl = 2 i for BaCl2= 3

Therefore TF(BaCl2) =3 2

32

= ,

TFfor BaCl2= 3 C ,Freezing Point of BaCl2 Solution isTF = 3 C.

Q. 4.Why water cannot be separated completely from ethyl alcohol by fractionaldistillation?Ans. Ethyl alcohol and water (95.4% ethyl alcohol and 4.6% water) form constant boilingmixture (azeotrope) boiling at 351.1 K. Hence, further water cannot be separated completefrom ethyl alcohol by fractional distillation.Q. 5.Why a person suffering from high blood pressure is advised to take minimum

quantity of common salt ?Ans. Osmotic pressure is directly proportional to the conc. of solutes. Our body fluid conta number of solutes. On taking large amount of salts, ions enter the body fluid there by

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raising the conc. of the solutes. As a result osmotic pressure increases which may rapture t blood cells.Q. 6.Chloro acetic acid is a monoprotic acid and has K a = 1.36 10 3. Calculate b. p. of 0.01 M aqueous solution? (K b = 0.51 k kg/mol)

Q. 7.Which colligative property is preferred for the molar mass determination of macromolecules ? Why ?Ans. Osmotic pressure is preferred over all other colligative properties because :(a) even in dil. soln theo. p.values are appreciably high and can be measured accurately.(b) o. p.can be measured at room temp. on the other hand elevation in B. P. is measuredat high temp. where the solute may decompose. The depression in freezing point is measuat low temp.Q. 8. How much ethyl alcohol must be added to 1 litre of water so that the solution willfreeze at 14 F ?(K f for water = 1.86 C/mol)Ans. (14 32) / 9 = C / 5

C = 5 ( 18) / 9= 10 C

TF =F b

a b

K 1000 WW M

W b= mass of solute

M b= molar mass of solute

Wa= mass of solvent10 = b

1.86 1000 W

1000 46

W b = 247.31 gQ. 9. 75.2 g of phenol is dissolved in solvent of K F = 14, if the depression in freezingpoint is 7 k. What is the % of phenol ?

Ans. K b= 0.51 k kg/mol = K a / C

= 1.36 10 3/ 0.01= 0.3687

i = 1 += 1 + 0.3687 = 1.3687T b

= i K b

m= 1.36 10 2 .51= 0.0069 C

Ans. K F= 14

M b=F 2

1 F

1000 K WW T

Taking the solvent as 1 kgM b=

1000 14 75.2

1000 7k

= 150.4 g per mol phenol (molar mass) 94 g/mol

i =Calculated molar massObserved molar mass

= 94 / 150.4 = 0.625

2 C6H5OH (C 6H5OH)21 0

1 / 2Total = 1 + / 2

= 1 / 2i = 1 + / 2

= 1 / 2 = 0.625/ 2 = 0.375

= 0.75% of association = 75%

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Q. 10. How many ml of 0.1 M HCl are required to react completely with 1 gm mixtureof Na2CO3& NaHCO3containing equimolar amounts of both ? Ans.

Q.11 Given below is the sketch of a plant for carrying out a process.

Ans. (i) The process is calledReverse Osmosis. [Reverse Osmosis:If the pressure appliedon solution side exceeds the osmotic pressure then theosmosiscan be reversed (i.e. puresolvent can be forced out of the solution to pass through the pores of membrane in opposidirection). This is calledReverse osmosis].(ii) The solvent moves from sea water container to fresh water container.(iii) Cellophane (It is one of the semi-permeable membranes that can be used)

(iv) This process is used for desalinationof sea water.Q.12 On increasing the temperature the solubility of most of the gases in waterdecreases. An important consequence of this effect is thethermal pollution of water , suchas occurs around power plants cooled by a river or stream. How is the survival of fishaffected by thermal pollution of water?Ans.: When the water temperature of the river or stream is increases the solubility of oxygin water decreases. Due to this decrease in dissolved oxygen the survival of fish becomesdifficult .Q.13 How much NaOH is required to preapre 50 ml of aqueous solution with 70mg of Na+ ions per ml. of the solution?Ans. : Na+ ions in 1 ml = 70 mg Na+ ions in 50 ml = 70 50 = 3.5g

Let the amount of Na2CO3be x

Let the amount of NaHCO3be 1 xSince no. of moles of both are equal

2 3 3

x 1 xN(Na CO ) M(NaHCO )

=

x 1 x

106 84

=

84 x = 106 106 xx = 0.5578xNa2CO3= 0.5578 / 106= 0.00526

xNaHCO3

= 0.00526

Na2CO3+ 2 HCl 2 NaCl + CO2+ H2 NaHCO3+ HCl NaCl + CO2+

H2OM1V1= 2 M2V2+ M3V30.1 V1= 2 0.00526 + 0.00526

V1 =0.01578

0.1

= 0.1578 LV = 157.8 ml.

(i) Name the process occurring in theabove plant(ii) To which container does the net flowof solvent take place

(iii) Name one SPM which can be usedin this plant(iv) Give one practical use of the plant

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Ans:- Molality of a solution depends on the mass of solvent and man does not vary withchange in temp. where as molarity depends on volume of solution and volumechange with change in temp.

Q10. What are azotropes?Ans:- A liquide mixture which distills over without changes in composition is called

ozeotropes or ozeotropic mixture.Q11. What are maximum boiling azeotropes? Give one example?Ans:- A mixture which boils at temp. brighter than the boiling point of its components the

mixture is known as maximum boiling azeotropes. Eg- a mixture of HCl and H2Ocontaining 20.2% of HCl by weight.

Q12. What are minimum boiling azeotropes? Give one example?Ans:- A mixture which boils at temp. lower than boiling point of its components the

mixture is known as minimum boiling azeotropes. E.g water and Benzene.Q13. What is expected value of i for K 4[Fe(CN)6] in dilute solution?Ans:- Expected value of n in K4(Fe(CN)6) is 5.Q14. What are isotonic solutions?Ans:- Those solutions are said to be isotonic which have the same osmotic pressure.Q15. Define molal elevation constant or ebullioscopic constant.Ans:- It is equal to the elevation in boiling point of1 molar soln. i.e one mole of a solute

dissolved in 1 kg of the solvent.Q16. What are non-ideal solutions? Explain as to why non-ideal solutions deviate from

Raoults Law.Ans:- Non ideal solution are those which do not obey Raoults law.

When the molecular interaction between solute molecules solvent. Solvent moleculesis not same as the molecular interaction between solute & solvent molecules thendeviotion occurs.

Q17. What are colligative properties? Mention them.Ans:-these are the colligative properties.

(a) Osmotic pressure (b) Relative lowering of vapour pressure(b) Elevation in B.P (d) Depression in F.P

NUMERICALSQ1. Calculate the mole fraction of ethylene glycol (C2H6O2) in solution containing 20 %

of ethylene glycol by mass.Ans:-

Mole fraction of ethylene glycol =262.......

.....

O H ofC molesof Nowater of molesof No

glycol theleneof moleof no

+

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mol-1K -1)Ans:-

We know nRT V =

Or atm022.21

2.022930821.035.0

2930821.0)2

1.025.0(2.0

=

=

+=

Q5. 2 g of benzoic acid (C6H5COOH) dissolved in 25 g of benzene shows a depression infreezing point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mol-

1. what is the percentage association of acid if it forms dimmer in soln.?Ans:-

Given that

WB=2g , K f =4.9 KKgmol-1, WA=25 g, K T f 62.1=

We have198.241

2562.19.4100021000 =

=

= gmol W T

K W M

A f

f B B

Also 2C6H5COOH (C6H5COOH)2

Initially 1 0( 1-x) x/2 mole

Total no. of particles at equilibrium. =2

12

)1(x x

x =+

21

xi =

Now i=(Normal molecular mass/Abnormal molecular mass)=122/241.98

Thus 122/241.98=1- x/2Or x/2 =1- (122/241.98) =0.4958So x = 0.9916The degree of association of benzoic acid in benzene is 99.16 %

***************

FOR BELOW AVERAGE01 Mark questions

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1. State Henrys law.2. Define osmotic pressure.3. How pressure effect the solubility of a solid in a liquid.4. State Raoults Law for a binary solution containing volatile components.5. Define Henrys law about solubility of a gas in a liquid.6. Define Vant Hoff factor.7. What do you understand by colligative properties?8. Define an ideal solution.9. State any two characteristics of ideal solution.10. Distinguish between molarity and molality.11. What is a non- ideal solution?12. Mention a large scale use of the phenomenon called reverse osmosis.13. What is antifreeze? Give one example.14. When is the value of Vant Hoff factor less than 1?15. Name the two factors on which the vapour pressure of the liquids depend.16. Define mole fraction of a substance in a solution17. When is the value of Vant Hoff factor more than 1?

FOR AVERAGE

1. Why is the elevation in b.p. of water different in the following solutions? (i) 0.1 NaCl solution (ii) 0.1 M Sugar solution.

2. What are azotropes?3. What happens when blood cells are placed in pure water?4. Why is the cooking temperature in pressure cooker higher than in open pan?5. Why does molality of a solution remain unchanged with change in temperature wh

its molarity changes?6. Why is ether not miscible in water?7. What are maximum boiling azeotropes? Give one example?8. What are minimum boiling azeotropes? Give one example?9. Why do doctors advice gargles by saline water in case of sore throat?10. Why is boiling point elevated when a non volatile solute is added?11. A person suffering from high blood pressure should take less common salt, why?12. Why do gases always tend to be less soluble in liquids as the temperature is raised?

FOR ABOVE AVERAGE1. How mole fraction of a solute and molality are related?

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2. Two liquids A and B boil at 145C and 190C respectively. Which of them has ahigher V.P. at 80C?

3. What is expected value of i for K 4[Fe(CN)6] in dilute solution?4. How molarity and molality of solute are related.5. What possible value of i will it have if solute molecules undergo association

solution.6. Define molal elevation constant or ebullioscopic constant?7. Define molal depression constant or cryoscopic constant?8. Why is osmotic pressure considered as a colligative property?9. On mixing equal volumes of water and ethanol what type of deviation would y

expect from Raoults Law?10. What are isotonic solutions?

FOR BELOW AVERAGE02 Marks question

1. Under what condition Vant Hoff factor is (i) equal to one, (ii) greater than 1, (iii) lthan 1.

2. Two liquid A and B on mixing produce a warm solution. Which type of deviatifrom Raoults Law does it show?

3. What are non-ideal solutions? Explain as to why non-ideal solutions deviate froRaoults Law.

4. What are colligative properties? Mention them.5. Differentiate between molarity and molality of a solution. When and why is molal

preferred over molarity in handling solutions in chemistry?

FOR AVERAGE1 Name the factors which affect the vapour pressure.2. Amongst the following compounds, identify which are insoluble, partially soluble a

highly soluble in water.(a) Phenol (b)Toluene (c) Formic Acid (d)Ethylene Glycol(e)Chloroform (f) Pentanol

3. What do you mean by relative lowering of vapor pressure ? How is relative lowerinof vapor pressure related with mole fraction of non volatile solute in a solution?

4. With the help of a suitable diagram show that the vapour pressure of a solution islower than the pure solvent, causes a lowering of freezing point for the solutioncompared to that of the pure solvent.

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5. Carbon tetra chloride and water are immiscible where as ethanol and water aremiscible in all proportions. Correlate this behaviour with molecular structures of thecompounds.

FOR ABOVE AVERAGE1. What do you mean by abnormal molecular mass? What are its cause?

2. With the help of suitable diagrams, illustrate the two types of non ideal solutions.3. State Raoults law for solutions of non volatile solutes in volatile solvents. Derive

mathematical expression for this law.4. What is osmotic pressure and how is it related with the molecular mass of non-vola

solute?5. What is meant by abnormal molecular mass of solute? Discuss the factors which br

abnormality in the experimentally determined molecular masses of solutes usin

colligative properties.6. State Raoults Law. Discuss the factor responsible for the deviation from this law.7. State Henrys Law and mentions some important application.8. Explain the significance of Henrys Constant (K H). At the same temperature,

hydrogen is more soluble in water than helium. Which of them will have a highvalue of K H and why?

9. Explain the difference between osmotic pressure and vapour pressure of a solution.

10. Give one example each of miscible liquid pairs showing positive and negativdeviation from Raoults Law. Give one reason each for such deviations.

FOR AVERAGE/BELOW AVERAGE02 Marks question (Numerical)1. The vapour pressure of pure liquid A and B are 450 and 700 mm Hg respectively

350 K. Find out the composition of the liquid mixture if total vapour pressure is 6

mm Hg.2. Calculate the mass percentage of aspirine(C9H8O4) in acetonitrile(CH3CN) when 6.5 g

of C9H8O4 is dissolved in 450 g of CH3CN.3. H2S, toxic gas with rotten a like smell, is used for qualitative analysis. If the solubili

of H2S in water at STP is 0.19 m. Calculate Henrys law constant.4. 18 g of glucose is dissolve in 1 kg of water in a saucepan. At what temperature w

water boil at 1.03 bar? K bfor water is 0.52 K kg mol-1.

5. An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at tnormal point of the solvent. What is the molar mass of the solute?

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*************************

STUDY MATERIAL

28

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Q1. Define molar conductivity. How does it varies with dilution ?Ans:- Molar conductivity:-It is the product of specific conductivity and volume of solution containing 1 g molecular mass of the electrolyte.

C K

mol 1000=

Unit= Sm2 mol-1

* Variation :-

Strong Electrolyte:-Molar conductivity increases slowly with decrease in concentration.

Weak Electrolyte:- Molar Conductivity increases sharply for weak electrolyte on dilution.Q2. States Koahlrausch law.Ans:- Limiting molar conductivity of an electrolyte is the sum of molar conductivity of caand anion at concentration approaches zero.

000

+=mol

0+ =Molar Conductivity of cation

0

=Molar Conductivity of anion

Q3. Wat do you mean by fuel cell? Write cathode and anode reaction in fuel cell.Ans:- Fuel Cell:- These are electrical cells which can convert the energy of combustion of

a fuel like (H2, CO etc.) directly into electrical energyEx:-H2-O2 fuel cell.

Reaction :-Anode reaction:- H2(g)+2OH-(aq) --- 2H2O+2e.X 2Cathode reaction:- O2(g) +2H2O+4e ---- 4OH-

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Overall reaction :-2H2(g) + O2(g) ------ 2H2O(l)

Q3. What do you mean by Corrosion? How it is a electrochemical phenomena?Ans:- in corrosion a metal is oxidized by a lose of electrons to oxygen and metal oxide isformed. It is an electrochemical phenomenon.

Chemistry of corrosion of iron:-The sport where iron under goes oxidation is considered as anode.At anode: 2Fe ---- 2Fe2+ + 4e-

At another sport on the metal these electrons reduce oxygen in presence of H+.At anode :O2(g) + 4H+ + 4e- ---- 2H2O(L)

The overall reaction is2Fe + O2 + 4H+ ----- 2Fe2++ 2H2OThe ferrous ions formed are further oxidized to ferric ions by atmospheric oxygen a

products comes out as rust in the form of Fe2O3XH2O(hydrated Ferric oxide)

Q4. A solution of CuSO4 is electolysed for 10 minutes with a current of 1.5 amperes. What isthe mass of copper deposited at cathode?Ans:- t= 10X60=600 Sec.

I=1.5 amperes.Q=nF

(Cu2++2e --- Cu)=2X96500CQ=It=1.5X600

=900 C2 X 96500 C charge deposited 63 g of copper

900 C charge deposited965002

90063

gm of copper

=0.2938 gm.Q5. The resistance of a conductivity cell containing 0.001 M Kcl solution at 298 K is 150

. What is the cell constant If conductivity of 0.001 M Kcl solution 298 K is 0.148 X10-3 S cm-1.

Ans:- R=1500K=0.148 X 10-3 S cm-1

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=al Cell Constant = ?

=al RK

=1500 X 0. 148 X 10-3

=0.222 Cm-1

Q6. Conductivity of 0.00241 M acetic acid is 7.896 X 10-5 Scm-1. Calculate its molar conductivity and if 0 for acetic acid 390.5 Scm2 mol-1. what is its dissociation

constant?Ans:-

K=7.896 X 10-5 S cm-1

20 5.390 Scm=

C K C 1000=

93.32241

7896

00241.0

100010896.7 5 ==

=

522

0

1085.100241.0)0838.0(

0838.05.390

93.32

===

===

C K

C

Q7. Represent the cell in which the following reaction takes place.

Mg(S) + 2Ag+(0.0001 M) ----- Mg2+(0.130M) + 2Ag(s)Calculate its E.M.F when E0=3.17V

Ans:- Cell reactionMg ----- Mg2++ 2e -- - - - - Oxidation at anode2Ag+ + 2e --- 2 Ag --- - - - - - -Reduction at cathodeRepresentation of cell

MgMg2+(0.130 M) Ag+(0.0001 M) AgC1 C2

E.M.F of the cell E= 12log

591.0

C

C

n E +

=3.17 +[ ][ ]+

+

2

2

log2

0591.0

Mg

Ag

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=3.17 + ( )130.0)0001.0(

log2

0591.0 2

=3.17 -0.21E=2.96 V

Q8. mol 0 for NaCl, HCl and Na AC(CH3COONa) are 126.4, 425.9 and 91.0 Scm2 mol-1

respectively. Calculatemol 0 for HAC(CH3COOH, Acetic Acid).

Ans:-

4.1269.5164.1269.4250.91

00000#

00

=+=+++= +++ Cl NaCl H NaCOOCH HAC

=390.5 Scm2 mol-1

Q9. States Faradays laws of electrolysis.Ans:1st law:- The amount of substance deposited during electrolysis is directly

proportional to quantity of electricity passed.m Q, m=Z Q

=ZitWhere Z=electrochemical equivalent.

2nd law:- If same change is passed through different electrolytes, the mass of substancedeposited at each electrodes will be propositional to their equivalent weights.W1/E1=W2/E2Where W is mass of substance and E is its equivalent weight.

Q10. Calculate G0 for Zn-Cu cell at standard conditions.

Given C F V E V E CuCun Zn 96500,34.0/,76.0/ 22 020 =+== ++

Ans:-

1

0

000

2.2129650010.120

10.176.034.0)76.0(34.0

=

==

=

+=+=

=

kjmol cV F nE G

V

E E E anodeCathodecell

Q11. Depict the galvanic cell in which the reaction

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Q. 5. Rusting of iron is quicker in saline water than in ordinary water. Why is it so ?

Ans. In saline water, NaCl helps water to dissociate into H+ and OH . Greater the number of H+, quicker will be rusting of Iron.

Q. 6. What would happen if the protective tin coating over an iron bucket is broken in

some places ?Ans. Iron will corrode faster as the oxidation potential of Fe is higher than that of tin.

Q. 7. Can a nickel spatula be used to stir a solution of Copper Sulphate ? Justify youranswer.(ENi+/Ni= 0.25 V ECu+/Cu= 0.34 V)

Ans. Reduction potential of Ni is less than Cu. Ni will replace the Cu from CuSO4. Thus Nispatula cannot be used to stir a solution of CuSO4.

Q. 8. Which out of 0.1 M HCl and 0.1 M NaCl, do you expect have greaterm andwhy ?

Ans. 0.1 M HCl will have greater m because H+ (aq) being smaller in size than Na+ (aq)and have greater mobility.

Q. 9. Three iron sheets have been coated separately with three metals A, B, C whosestandard electrode potentials are given below :

A B C Iron

Evalue 0.46 V 0.66 V 0.20 V 0.44 V

Identify in which rusting will take place faster when coating is damaged.

Ans. Rusting of iron will take place when coated with metal C as it is placed above iromore than other metal.

Q. 10. Which will have greater molar conductivity ? Solution containing 1 mol KCl in200 cc or 1 mol of KCl in 500 cc.

Ans. 1 mol of KCl in 500 cc.

2 MARKS QUESTIONS

Q. 1. (a) How will the value of Ecell change in an electrochemical cell involving thefollowing reaction of the concentration of Ag+ (aq) is increased ?

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(b) What will be e. m. f. when the cell reaches equilibrium :

Mg (s) + 2 Ag+ (aq) Mg2+ (aq) + Ag (s)

Ans. (a) Ecell= Ecell 0.059

2log

2

2

Mg

Ag

+

+

As the concentration of [Ag+] ion increases, Ecellincreases.

(b) e.m.f. = 0

Q. 2. (a) In a cell reaction, the equilibrium constant K is less than one. Is E for thecell positive or negative ?

(b) What will be the value of K of Ecell= 0 ?

Ans. For a cell E =0.0591n

log K

K < 0 log K < 0

i.e. log K is ve.

Then Ecellwill be negative.

(b) If Ecell= 9 then 0 =0.0591

n log K

log K = 0 K = 1

Q. 3. Knowing that :

Cu2+ (aq) + 2 e Cu (s) E = + 0.34 V

2 Ag+ (aq) + 2 e 2 Ag (s)E = + 0.80 VReason out whether, 1 M AgNO3 solution can be stored in Copper Vessel or 1 MCuSO4 solution in Silver Vessel.

Ans. A solution of an electrolyte can be stored in a particular vessel only in case there is chemical reaction taking place with the material of the vessel.

Cu is a strong reducing agent and can lose electrons to Ag+ as E of Cu is less thanthat of Cu. So AgNO3 cannot be kept in Copper Vessel.

CuSO4 solution can be stored in Ag Vessel as no chemical reaction will take place asAg is placed above Cu in the activity series and Ag is less reactive than Copper.

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A

B

400

200

0.2 0.4C

m

Q. 4. What is the number of electrons in one Coloumb of electricity ?

Ans. Charge on one mole of electrons = 1 F = 96500 C

96500 C of Charge is present on electrons = 6.022 1023

1 C of Charge is present on electrons =236.022 10

96500 C

1 C

= 6.24 1018

Q. 5. Which of the following pairs will have greater conduction and why ?(a) Copper wire at 25 C and Copper wire at 50 C.

(b) 0.1 M acetic acid solution or 1 M acetic acid solution ?

Ans. (a) Copper wire at 25 C because with increase in temperature metallicconduction decreases due to vibration of kernels.

(b) 0.1 M acetic acid solution because with dilution degree of dissosciationincreases and hence no. of ions.

3 MARKS QUESTIONSQ. 1. The following curve is obtained when molar conductivity (m) is plotted against

the square root of concentration for 2 electrolytes A and B.(a) What can you say about the nature of the two electroyltes A and B ?(b) How do you account for the increase in molar conductivitym for the

electrolytes A and B on dilution ?

Ans. (a) A is a strong electrolyte and B is a weak electrolyte.

(b) Molar conductivity of a strong electrolyte (A) increases with dilution as ionmobility increases. In a weak electrolyte molar conductivity increases steeplwith dilution as degree of dissociation increases and hence no. of ionsincreases.

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Q. 2. Iron and nickel are used to make electrochemical cell by using a salt bridge to join a half cell containing 1 M Fe2+ (aq) in which a strip of iron has beenimmersed to a second half cell which contains 1 M Ni2+ (aq) in which a strip of Nihas been immersed ? A voltmeter is connected between the two metal strips :EFe+/Fe= 0.44 V ENi+/Ni= 0.25 V

(a) Write the name of the cathode and anode.

(b) Write the half reactions involved ?

(c) What would be the effect on the Voltmeter reading if Fe2+ concentrationwere increased ?

Ans. (a) Anode : Fe

Cathode : Ni

(b) Reaction at anode : Fe Fe2+ + 2 e

Reaction at cathode : Ni2+ + 2 e Ni

(c) Voltmeter reading decreases.

Q. 3. Consider the electrochemical cell :

Zn (s) / Zn2+ (aq) // Cu2+ (aq) / Cu. It has an electrical potential of 1.1 V whenconcentration of Zn2+ and Cu2+ ions is unity.

State the direction of flow of electrones and also specify if Zinc and Copper aredeposited or dissolved at their respective electrodes. When :

(a) an external opposite potential of 0.8 V is applied.

(b) an external opposite potential of 1.1 V is applied.

(c) an external opposite potential of 1.4 V is applied.

Ans. (a) Electrons flow from Zn rod to Cu rod.

Zinc dissolved and Copper gets deposited.(b) No flow of electrons and current.

No change observed at Zinc and Copper electrodes (system is at equilibrium)

(c) Electrons flow from Cu rod to Zn rod.

Zinc is deposited and Copper gets dissolved.

Q. 4. Given that :

CO3+

+ e

CO2+

E = 1.82 V2 H2O O2 + 4 H+ +4 e E = 1.23 V

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Explain why CO3+ is not stable in aqueous solution ?Ans. The Ecellcan be calculated as :

4 [CO3+ + e CO2+] E = 1.82 V2 H2O O2 + 4 H+ +4 e E = 1.23 V

Cell reaction : 4 CO3+ + 2 H2O CO2+ O2 + 4 H+

Ecell= 1.82 V ( 1.23 V) = 3.05 V

Since Ecell is positive, the cell reaction is spontaneous. CO3+ iron will take part in thereaction and hence unstable in aqueous solution.

Q. 5. For the reaction :Ag+ + Hg Ag + Hg22+

E = 0.80 V E = 0.79 V

Predict the direction in which the reaction will proceed if :

[Ag+] = 10 1mol/h [Hg2+] = 10 3mol/hAns. Cell reaction is :

2 Ag+ + 2 Hg 2 Hg + Hg22+

Ecell

= Ecell

0.05912

log2

2

2

Hg

Ag

+

+

= (0.80 V 0.79 V) 0.0591

2log ( )

3

21

10

10

= 0.01 V 0.05912

( 1) = 0.01 + 0.0295

= 0.0395 VSince Ecellis positive, the reaction will be spontaneous in the forward direction.

FOR ABOVE AVERAGE01 Marks Questions

1. Express mathematical relationship among resistance(R), Specific conductivity (K)and cell constant.

2. Write relation between specific conductance and molecular conductivity of anelectrolytic.

3. State the Kohlrausch law.4. Name a metal that can be used for the cathodic protection of iron against rusting.

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5. How are secondary cells different from primary cells?6. Write the reaction occurs in fuel cell.

7. What do you mean by standard electrode potential?8. What is galvanization of iron?9. Define strong electrolytes.10. Define molar conductivity.

02 Marks Questions1. What is corrosion? How is rusting of iron protected by cathodic protection.2. How is cathodic protection different from galvanization in protection of iron fro

rusting?3. What do you understand by equilibrium constant? Calculate the equilibrium

constant of the reactionCu (s ) + 2Ag+ (aq) Cu2+ (aq) + 2Ag (s) E = 0.46 v .

4. Represent Zn Cu cell and write Nernst equation for the calculation of emf of thecell.

5. The conductivity of 0.2M solution of NaCl at 298 K is 0.0248 S cm-1. Calculate itsmolar conductivity.

6. The standard electrode potential for Daniell cell is 1.1v. Calculate the standaGibbs energy for the reactionZn (s) + Cu2+(aq) Zn2+(aq) + cu (s)

7. State and explain the Faradays laws of electrolysis. What is the value oFaradays constant?

8. State reasons for the following Rusting of iron is said to be an electrochemical phenomena. Rusting of iron is quicker in saline water than in ordinary water. Arrange the following metals in the order in which they displace each from

the solution of their salts.Al, Mg, Fe, Cu, Zn

03 Marks Questions1. Write the Nernst equation and calculate theemf of the following cell at 298 K.

Cu(s) / Cu2+ ( 0.130 M ) // Ag+ ( 1 x 10-4 M ) / Ag (s). Given that E0 Cu+2 / Cu =0.34 V and E0 Ag+ / Ag = 0.80 V, F = 95500 C Mol-1

2. What is standard hydrogen electrode? How it measures the electrode potential of electrode? Explain.

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3. What are secondary cells? Explain lead storage battery with electrode reactions.4. A galvanic cell is constructed in which the cell reaction is

Zn(s) + 2 Ag+ (aq) Zn2+(aq) + 2 Ag (s), Now write:(a) Which of the metal electrode is negatively charged?

(b) The direction of the current (either anode to cathode or cathode to anode)(c) Individual half electrode reaction for cathode

5. What are electrode potential andemf of a cell?Calculate theemf of the cellMg(s) / Mg2+( 0.1 M ) // Ag+ ( 0.01 M ) / Ag at 250 CGiven that E0 Ag+ / Ag = 0.8 V, E0 Mg2+ / Mg = - 2.37 V

05 Marks Question

1. What is EMF of a cell?Calculate the emf of the cellMg(s) / Mg2+( 0.1 M ) // Ag+ ( 1 x 10-4 M) / Ag (s) at 250 C,Given that E0 Ag+ / Ag = 0.8 V , E0 Mg2+ / Mg = -2.37v

2. What will be the effect on EMF of the cell if concentration of Ag+ is increased to 1 x 10-3M?

3. Explain the product of electrolysis of molten NaCl and aqueous NaCl. Explain t

difference between these two phenomena and list two other application of electrolys4. A cell is formed as Ni (s) / Ni2+( 0.01 M ) // Cu2+( 0.1 M ) / Cu(s)

The E0 values for Ni2+ / Ni and Cu2+ / Cu electrodes are -0.25 V and 0.34 Vrespectively.Calculate the cell potential, equilibrium constant and work done by the cell.

5. Electrolysis of aqueous sodium chloride gives H2 gas at cathode instead of sodium mand Cl2 gas anode while electrolysis of molten NaCl gives sodium metal at cathodHow is this difference in results explained? Give electrode reactions for anode ancathode.

FOR BELOW AVERAGE01 Mark Questions

1. What is over voltage in an electrolytic reaction?

2. What is Nickel- Cadmium cell?3. How is unit of molar conductivity arrived at?

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4. How many faradays of electricity are required to liberate 2 moles of hydrogen gaselectrolysis of a solution ?

5. Why does cu not displace Fe from FeSO4 Solution?6. Why does an alkaline solution enhance the rusting of iron?7. What is concentration cell? Give an example.

8. In function of a galvanic cell, one of its electrodes does oxidation reaction. Whatthe name of the electrode and what is its polarity?

9. What is the electrolyte used in a fuel cell?10. Suggest one method to operate galvanic cell if the salt bridge is absent.11. The standard reduction potential for the Zn2+ aq/Zn (s) half cell is -0.76 V. Write the

electrode reactions of the cell when it is coupled with standard hydrogen electrod(SHE). Also give the standard cell potential.

02 Marks Questions1. Why is it not allowed to determine the molar conductivity at infinite dilution of a w

electrolyte by extrapolating is allowed in the graph of strong electrolytes. Explain.

2. If E0 for copper electrode is +0.34V; how will you calculate itsemf when the solution incontact with it is 0.1 M in copper ions? How doesemf of copper electrode change whenconcentration of Cu2+ ions in solution is decreased?

3. Calculate the potential of a zinc - zinc ion electrode in which the zinc ion activity0.001M

[E0 Zn2+/Zn = -0.76 V, R= 8.314 JK -1mo1-1, F=96500 Cmo1-1]4. The molar conductance of sodiumacetate, hydrogenchloride and sodiumchloride

infinite dilutions are 91, 426 and 126 Simen cm2 mol-1. Calculate the molar conductanceof acetic acid at infinite dilution.

5. Estimate the minimum potential difference needed to reduce Al2O3 at 500c. The for the decomposition reaction2/3 Al2O3 4/3 Al + O2 is G = 960 KJ.

6. The E0 Values for two metal electrodes are given below(i) Cr 3+/Cr 2+= -0.4V (ii) Fe3+/Fe2+= 0.8V

Comment on the result of treating a solution of Cr (II) with a solution containinFe (III) ions

7. Calculate the standard free energy change for the reaction occurring in the cellZn|Zn2+(IM) // Cu2+(IM) / CuGiven E0zn2+/zn = -0.76V and E0 cu2+/Cu= 0.34V.

19. Explain the electrolysis of aqueous NaCl and molten NaCl with their Chemicreactions. Give reasons for this difference and deduce criteria for product formatio

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20. Explain the electrode reaction of a fuel cell. Discuss the advantage of fuel cell space programme.

03 Marks Question1. Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO3 With Ag electrodes.

(ii) A Dilute solution of H2SO4 With platinum electrodes.(iii) An aqueous solution of CuCl2 with platinum electrodes.

2. The resistance of a conductivity cell containing 0.001 M KCl Solution at 298 K1500 ohms. What is the cell constant if conductivity of 0.001 M KCl Solution at 2K is 0.146X10-3 S cm-1.

3. Conductivity of 0.00241 M acetic acid is 7.896X10-5 S cm-1, calculate its molar conductivity and if ^0m for acetic acid is 390.5 S cm2 mol-1. What is its dissociation

constant?4.. Rusting is an electrochemical phenomena. Explain this phenomena with the he

of rusting of iron with reactions involved.5. Silver is electrodeposited on a metallic vessel of surface area 800 cm2 by passing

current of 0.2 ampere for 3 hours. Calculate the thickness of Silver deposited.(Density of Ag =10.47 g cm-3, Atomic mass of Ag=108 amu)

05 Marks Question

6. Calculate the potential of following cell reaction at 298 K Sn4+(1.50 M)+ Zn Sn2+(0.5M)+ Zn2+(2M)The standard potential E0; of the cell is 0.89V, whether the potential of the cellincrease or decease (R=8.314 JK -1mol-1, F=96500 C mol-1) if the concentration of Sn2+ is increased in the cell.

7. The conductivity of NaCl at 298 K has been determined at different concen-tration andresults are given below:

Concn

/ M 0.001 0.010 0.020 0.050 0.100102 x K/S m-1 1.237 11.58 23.15 55.53 106.74Calculate ^m for all concentrations and draw a plot between ^m and C1/2. Find tvalue of ^m.

8. (a) State the reasons for the following :-a. Iron does not rust even if Zinc coating is broken in a galvanized iron

pipe. b. Electrolysis of KBr (aq) gives Br2 at anode, but that of KF (aq) does

not give F2.(b) Write the electrode reaction of H2-O2 Cell.

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(c) Calculate the EMF of the following cell at 298 K Sn/Sn2+(0.1M) // Ag+(0.1M) / AgGiven E0 Sn2+/Sn = -0.14V, E0 Ag+/Ag = 0.8V

9. (a) State Kholrauschs law for electrical conductance of an electrolyte at infinidilution.

(b) Give the composition and reaction of cathode and anode in a mercury cellGive one use.

(c) Silver is electrodeposited on a metallic vessel by passing a current of 0.ampere for 3 hours. Calculate the weight of silver deposited.

(Atomic mass of Ag=108 amu)FOR AVERAGE01 Mark Question

1. Define the molar conductivity of an electrolytic solution.2. Express the relation between degree of dissociation of an electrolyte and its molar

conductivities.3. What does the standard electrode potential of a metal being negative E0

Zn2+/Zn = - 0.76 v shows?4. What happens when the protective coating of galvanized iron is broken?5. How is electroplating different from galvanization?

6. How does a fuel cell operate?7. How much charge is required for the following reduction of 1 mol of Cu2+ions to cu

(s)?8. Which type of metal can be used for the cathodic protection of iron?9. Give one difference between primary and secondary cells.10. What are uses of salt bridge in a galvanic cell?02 Marks Question

1. What is mercury cell? Give an electrode reaction?2. Make difference between molar conductivity and equivalent conductivity.3. Suggest a cell to determine molar conductivity experimentally.4. How will you explain the sharp increase in molar conductivity of a week electroly

on dilution? How is molar conductivity related to the degree of dissociation?5. The conductivity of 0.20 M solution of potassium chloride 298 K is 2.48 x 10-2 ohm-1

cm-1 calculate the molar conductivity ?

6. A solution of Ni (NO3)2 is electrolyzed between platinum electrodes using a currof 5 A for 20 minutes? What mass of Nickel is deposited at the cathode?

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7. The Zinc - silver oxide cell has the following reactions.Zn Zn2++ 2 e- E0= 0.76 vAg2O + H2O + 2e- 2Ag+ + 2OH- E0=0.34V

Calculate the standard free energy in joules8. Give reason for the following phenomena:

(i) Iron does not rust if coating is broken in a galvanized iron pipe.(ii) Rusting is said to be an electrochemical phenomena

9. Molar conductance of a 1.5 M solution of an electrolyte is found to be 138 simen c2.What would be specific conductance of this solution?

10. What is rusting? Explain how galvanization gives better protection than electroplatfor an iron object from rusting?

11. Describe the characteristics of variation in molar conductivities (^m) strong and w

electrolytes on dilution.03 Marks Question1. Given E0 Cu2+ / Cu = 0.34 volt and E0 Ag+ /Ag = 0.80 volt for a cell

a) Calculate cell potential for the cell containing 0.1 M Ag+ and 4 M Cu2+ at 25C. b) How many hours does it take to reduce 3 moles of Fe2+with 2 amp current.

2. Calculate the standard cell potential, standard free energy charge rG0 and equilibriumconstant for the Galvanic cell 2Cr(s) + 3 Cd2+ 2Cr 3++ Cd

Given that E0

Cr 3+

/Cr = -0.74 v, E0

Cd2+

/Cd= -0.40 v3. Define conductivity and molar conductivity for the solution of an electrolyte. Disc

their variation with concentration.4. The resistance of a conductance cell containing 7.5 x 10-3 M solution of KCl at 250 C.

was 1005 ohms.Calculate the specific conductance and molar conductance of the solution if ceconstant is 1.25 Cm-1.

5. What happens during the corrosion of a metal? Explain the electro-chemical basiscorrosion of iron with chemical equation involved?05 Marks Question1 What is EMF of a cell? How is it different from cell potential (Ecell)? Calculate t

EMF of the cell reactionSn4+(1.5M) + Zn Sn2+(0.5 M) + Zn2+(2M )The standard cell potential of the cell is 0.89 v.

2. Explain the primary and secondary batteries. How are secondary cells different fr primary cells? Give the composition and reaction of cathode and anode in a mercucell?

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3.. What do you mean by molar conductivity and equivalent conductivity? Explain experimental Determination of molar conductivity with help of conductivity cell.

4 In the electrolysis of aqueous solution of sodium chloride, there are two possibanode reactions.

2Cl- (aq) Cl2 + 2e- E0 = 1.36 v

2 H2O (l) O2 (g) + 4H+

(aq) + 4e-

E0

= 1.23 vWhich of the above reaction actually takes place and why? Also give other utilitieselectrolysis?

********************

STUDY MATERIAL

Chemical Kinetics :Study of chemical reactions w.r.t. reaction rate, effect of variousvariables, rearrangement of atoms and formation of intermediates.

Rate of Reaction :It is concerned with decrease in concentration of reactant per unit time.Rate = - d[c]/ dt

It can also be defined as increase in concentration of products per unit time.Rate= d[p]/ dt

Average Rate:It is rate of reaction measured over a long time interval.Average Rate = X/ t

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UNIT 04CHEMICAL KINETICS


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Instantaneous RatedT dX

T X

t Lt

=

0

i.e. rate of reaction when the average rate is taken over a very small interval of time.

Rate law or Rate equation :Rate law is relation between Rate of reaction and concentration

of reactants. [ ] [ ]y x B A K tion Rateofreac =

Mind always, it is not theoretical but it is written when order of reactions w.r.t. A & ordereaction w.r.t. B are known experimentally.

Rate Constant : It is defined as rate of reaction when molar concentration of reactant isunity.

Molecularity : Total number of molecules of the reactants in an elementary reaction(Single step reaction) is called molecularity of reaction.Unimolecular reaction :When molecularity is one.

NH4 NO2 N2 + 2 H2OBiMolecular Reaction :When molecularity is two.

2HI H2+ I2

Trimolecular or Termolecular reactions :When three species collide2NO + O2 2NO2

Note that Molecularity greater than three is not observed? It is due to the probabilthat more than three molecules can collide and react simultaneously is very small. Hence,molecularity greater than three is not observed.

Order of Reaction :The sum of the powers of the concentration of reactants in the rate lawis termed as order of the reaction. It can be in fraction. It can be Zero.

Order of a reaction is an experimental quantity. It is applicable to elementary as was complex reactions where as molecularity is applicable only for elementary reactions.

For complex reaction, Order is given by the slowest step and generally, moleculariof the slowest step is same as the order of the overall reaction.

Zero order Reaction :Rate = K[A]oThe rate of a reaction does not change with the concentration of reactants.

First Order Reaction :The reaction in which the rate of reaction is directly proportionate tothe concentration of reacting substance.

Rate constant of first order reaction is xa

at

K

= log303.2

46

Rate = dx = k[A]dt


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or [ ][ ] A A

t K 0log

303.2=

Where a is initial concentration, (a-x) is the concentration of reactants after time The unit of K is s-1 or Min-1.

Half Life of a reaction :The time taken for a reaction when half of the starting material hasreduced is called half life of a reaction.

K t

693.02

1= Where K= rate constant

Second Order Reaction :[ ] [ ]11 B A K

dT dX

Rate ==

The reaction in which sum of powers of concentration terms in rate law or rate equation

equal to 2.Third Order Reaction : The reaction in which sum of powers of concentration terms inrate law is equal to 3 i.e.

[ ] [ ] y x B A K dT dX

Rate == , Where x+y =3

Pseudo First Order Reaction :The reaction which is bimolecular but order is one is calledPseudo first order reaction.

OH H C COOH CH O H H COOC CH H 5232523 + ++

Large Excess

Factors affecting rate of reactions :Rate of reaction is affected by

Nature of Physical Surface Concentration Temp.Reactants State Area

Reactions of fraction order : HBr Br H 2

22

+

[ ] [ ]2121

2Br H K Rate =

Half life of Reaction of nth Order :

In general, [ ] 1021

1n A

t where n is order of reaction.

For at 2

1 for Zero order t is independent for first order.

at 1

21 for second order.

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22

11

at for 3rd order.

Activation Energy (Ea) :It is extra energy which must be possessed by reactantmolecules so that collision between reactant molecules is effective and leads to formatof product molecules.

Arrhenius equation of reaction rate : RT

E ae A K

= .

Where K = rate constantA= frequency factor,Ea= Energy of activation,R = gas constant,T= temperature in Kelvin

lnK = lnA Ea/ RTlog K = log A- Ea/ 2.303 RT

Rate determining step:The slowest step in the reaction mechanism is called rate determining step.

Temperature coefficient :It is the ratio of rate costant at temperature 308 K to the rate constant at

temperature 298 K,Temperature Coefficient = Rate ConstantK at 308 K / Rate ConstantK at 298 K

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Q13. Write the Unit of K in Zero Order reaction.Ans.: M0L -1 S -1

Q14. What is the Unit of K in first order reaction.Ans. K=S-1

Q15. What is the unit of K in Second Order reaction?Ans. K=Mol-1.L.S-1

Q16. Write the determination of second order reaction?Ans. Molecularity is two & order of reaction is one.

Ex : OH H C COOH CH O H H COOC CH H 5232523 + ++

Q17. Identify the reaction order if the unit of rate constant is Sec-1.Ans. First order reaction.

Q18. What is the order of reaction of Nuclear reaction.Ans.: First Order reactionFor Average Students :01 Mark

Q1. State any one condition under which a bimolecular reaction may be kinetically of first ordeAns.:

02

1523

523523

][][ O H H COOC CH K Rate

OH H C COOH CH HOH H COOC CH

=

++

i.e. H2O is in excess.

Q2. Define activation energy.Ans.: It is defined as extra energy to be supplied to the reactants so that they canchange into products.

Q3. A reaction is 50% complete in 2 Hrs and 75% complete in 4 Hrs.What is the order of the reaction?

Ans. First Order.

Q4. The plot of log K versus X is linear with a slope = -Ea/ 2.303 R. What is X?Ans. X is 1/T.

Q5. The rate constant of a reaction is 1.2 x 10-2 L.Mol-1S-1. What is the order of thereaction ?

Ans.: Order =2For Above Average Students : 01 Mark

Q1. What is temperature coefficient ?

Ans.:298

308

R R

Q2. Fill up the blanks :..............

.

12

21

=T T

T T R

E a

Ans.:1

2

R R Ln

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Q3. A catalyst provides a path of . Activation energy.Ans. Lower

Q4. In a photochemical reaction, the energy of activation is provided by

Ans.: RadiationQ5. Which of the following graphs correspond to first order reaction ?

Ans.: (a)

Q6. Photochemical reaction between hydrogen & Chlorine on the Surface of water is a reaction(a) Zero Order, (b) First Order, (c) Second Order, (d) Third Order Ans. : Zero Order

Q7. For a chemical reaction XA yM.The rate law is r=K[A]3. If the concentration of A is doubled the reaction rate will be (a)

Doubled, (b) Quadrupled, (c) Increased by 8 times, (d) UnchangedAns.: (c)

CHEMICAL KINETICSBelow Average Students :02 Marks

Q1. Differentiate between order of reaction and molecularity of reaction.Ans.Order of reaction Molecularity1. It is defined as sum of powers to whichconcentration terms are raised in rate law

1. It is the number of molecules taking part inchemical reaction.

2. It is determined experimentally 2. It is determined theoretically3. It can be zero or even in fraction 3. It is always in whole number except Zero.4. Order of complex reaction can be determined, 4. Molecularity of complex reaction can not b

determined.

Q2. For a reaction A+H2O B, rate TA. What is itsi) Molecularity, ii) Order of reactions ?

Ans. I) Its molecularity is 2ii) Its order is 1.

Q3. Define pseudo unimolecular reaction. Give two examples.Ans.: The reaction which is molecular but its order is one is called pseudo unimolecular

reaction. Eg.:

612661262112212

5232523

.)2

.)1

O H C O H C O H O H C

OH H C COOH CH O H H COOC CH invertage

H

+ +

+ ++

Glucose Fructose

Q4. Name four factors affecting rate of reduction.

51

(a) (b) (c) (D)

Rate Rate Rate Rate

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Ans.: 1) Nature of reactants2) Temperature3) Concentration4) Catalyst

Q5. When could order an molecularity of a reaction i) be Same ii) be differentAns.: i) Order and molecularity will be same in single step reaction.

ii) They will be different if reaction is of two or more steps.For Average Students : 02 Marks

Q1. Plot a graph between log cone Vs time and give expression value of K.Ans. Slope= -K/2.303

Q2. The rate constant for a first order reaction is 0.005 min-1. Calculate its half life.

Ans.: Min K t 138605.0693.0693.0

21 ===

Q.3. What is meant by effective collision?Ans.: The collision which leads to formation of product. Molecules is called effective

collision.Q4. When do molecules undergo effective collision?Ans.: Molecules undergo effective collision if they cross energy barrier and orientation

barrier, that is they possess activation energy and collide in proper orientation.

Q5. How does concentration effect the rate of reaction?Ans,: When we increase concentration of reactants, total no. of collision will increase, therefo probability of effective collision will increase, hence the rate of reaction will increase.For Above Average Students : 02 MarksQ1. An increase of 10 K in temp. rarely doubles the kinetic energy of particles but

doubles the rate of reaction, why?Ans.: When temp. is increased 10 K , kinetic energy of molecules increases, no. of

molecules possessing activation energy become double, therefore no. of effectivecollision doubles hence rate of reaction.

Q2. The rate of constants of a reaction at 500 K & 700 K are 0.02 Sec-1 and 0.07 Sec-1 respectively. Calculate the values of Ea & A.

Ans.

61.1012.002.0

.02.0

,

8.1823010714.5

15.19544.0

15.1910

714.5544.0

500700500700

314.8303.202.007.0

log

.303.2log

500314.88.18230

14

4

11

21

12

1

2

===

=

=

=

=

=

=

Ae A

Ae K Since

J Ea

Ea

mol JK EaT T

T T

R

Ea

K

K

RT Ea

Log(Conc.)

time

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FOR BELOW AVERAGE STUDENTS :03 Marks

Q1. Drive the relation[ ][ ] R

o Rt

K log303.2=

Ans.: We know that rate of reaction is proportional to the first power of concentration of the reactant R. For Ex.

[ ] [ ]

[ ][ ] dt K R

Rd or

R K dt Rd

Rate

P R

., =

==

Integrating this equation, we getLn[R]=-Kt+ I -------------------(1)

Again;I is the constant of integration and its value can be determined easily,When t=0, R=[R 0], where [R 0] is the initial concentration of the reactant.Ln[R 0]=-K x 0 +ISo, Ln[R 0]=I

Substituting the value of I in Equation (1)Ln[R]= -Kt + Ln [R 0]

Rearranging this equation,[ ][ ]

[ ]

[ ] R R

Log t

K or

R R

Lnt

K or

Kt R R

Ln

0

0

0

303.2,

1,

=

=

=

Q2. Derive the expression t = 0.693/ K for first order reaction.

Ans,:

[ ]

K t

t K

R R

t K

R

R Log

t K

O

O

693.0

2log303.2

2

log303.2

303.2

21

21

21

0

=

=

=

=

FOR AVERAGE STUDENTS :03 Marks

Q1. Derive the relationship between activation energy & rate constant.Ans. Arrhenius equation RT E e A K

= . where A is frequency factor, Ea is activation

energy, R= 8.314 JK -1mol-1, T is temp. in Kelvin.

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=

=

=

=

=

21

12

1

2

211

2

2

1

.303.2log

11ln

lnln

lnln

lnln

T T

T T

R Ea

K

K

T T R Ea

K

K

RT Ea

Ak

RT EG

A K

RT Ea

A K

For Above Average Students : 03 MarksQ1. The following results have been obtained during the kinetic studies of the reaction.

2A + B C + D

Experimental [A] M [B] M Initial rate of formation of D/M min-11 0.1 0.1 6.0 x 10-3

2 0.3 0.2 7.2 x 10-23 0.3 0.4 2.88 x 10-14 0.4 0.1 2.4 x 10-2

Determined the rate law and the rate constant for the reaction.Ans.:

)4(]1.0[]4.0[1040.2

)3(]1.0[]1.0[100.6

2222

141

,),2/()1()2(]4.0[]3.0[102.7

)1(][][

2

3

2

2

=

=

=

==

=

=

y x

y x

y

y x

y x

K

K

yY

weget Dividing K

B A K dt dx

Dividing (3) by (2), we get,

12

213

21

0.6]1.0[]1.0[100.6

][][][][

141

41

==

==

==

S M K K

B A K B A K dt dx

x x

y x

Q2. Calculate the half life of a first order reaction from their rate constants given below :(a) 200 S-1 (b) 2 Min-1 (c) 4 year -1

Ans.: (a) .10465.3200

693.0693.0 31

21 Sec

S K t ===

(b) ..min35.0min465.32

693.01

21

=== Min

t

(c) yearst 173.04693.0

21

==

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Q3. Give the mechanism of the reaction)(2)()( 22 g HCl g Cl g H

Sunlight +

Ans.: Chain initiation step :Cl Cl Cl HN 2 +

Chain propagation step

Cl HCl Cl H HCl H Cl H ++

++

2

2

Chain termination stepQ4. State the role of activated complex in a reaction and state the relation with energy of activation.Ans.: When the colliding reactant molecules possess the kinetic energy equal to energy of activatthen the configuration of atoms of the species at this state is different from the reactants as well as products.This state is called activated or transition state and specific configuration of this statcalled activated complex.

The reactant molecules do not change directly into products, first they absorb energequivalent to the energy of activation and form an activated complex. The activated complex for

has a very short life spam and splits into the products. The activated complex is at the top of energy barrier graph and possess the highest energy. In this activated complex, all the bonds are intransition state.

Low energy activation barrier means the activated complex is readily formed and it is fareaction.

High energy of activation barrier means the activated complex is difficult to form and it islow reaction.

55

A.BActivated complex

Eaf Energy P RS o E E H =

ER JHoS

UNIT 05SURFACE


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STUDY MATERIAL

1. Adsorption:- It is the process of attracting molecular species on the surface of solidor liquid .

2. Adsorbate:- The molecular species which concentrates or accumulates on thesurface known as Adsorbate.3. Adsorbent:- The solid or liquid substance on which adsorption takes place knownas adsorbent .

4. Desorption:- The process of removal of adsorbed substance from a surface of solidor liquid known as desorption.

5. Absorption:- The uniform distribution of molecular throughout the bulk of the solidknown as absorption.

6. Sorption:- The process in which both adsorption and absorption takes placesimultaneously known as sorption.

7. Enthalpy of Adsorption:- The amount of energy released by the attraction of onemole of adsorbate on the adsorbent.

8. Types of adsorption:- There are two types of adsorption :(a) Physisorption or Physical adsorption :- When the gas molecules are attracted or accumulated on the solid by Vander waals forces.(b)Chemisorption or Chemical adsorption :- When the gas molecules are accumulated on thesolid by chemical bonds.

9. Freundlich adsorption isotherm:- He gave a relation between the quantity of gasadsorbed by unit mass of solid adsorbent and pressure at a particular temperaturex/m=k P1/n (n>1)Where x be the mass of adsorbate ,m be the mass of adsorbent k & n be the constantsP be the pressure .This relation can be changed at different Pressure:-At low pressure x/m=k P1At high pressure x/m=k P0At intermediate pressure x/m=k P1/n

10. Adsorption from solution phase:- It has similar relation with Freundlich adsorptionisotherm .Only in place of pressure ,concentration of solution is taken.Therefore x/m=k C1/n

11. Catalyst:- A substance which increase or decrease the rate of chemical reactionand quantitatively unchanged after the reaction known as catalyst. There are two types of catalyst:- (i) Positive Catalyst and (ii) Negative Catalyst.

12. Promters:- A substance enhances the activity of catalyst.13. Poisons:- A substance decreases the activity of catalyst.14. Homogeneous catalysis:- When reactants and catalysts are in same phase ,the process is known as Homogeneous catalysis.Eg. )(2)()(2 3)(22 g SO g O g SO g NO +

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15. Heterogeneous catalysis :-When reactants and catalysts are in different phases,this process is known as Heterogeneous Catalysis.

Eg.: N2(g) + 3 H2(g) Fe(S) 2 NH3(g)

16. Mechanism of heterogeneous catalysis:- The steps are as follows :(i) Diffusion of reactants on the surface of catalyst.(ii) Adsorption of reactants on the surface of catalyst.(iii) Chemical reaction between reactants on the solid surface to form intermediat

product.(ii) Desorption of product from solid surface.(iii) Diffusion of products away from solid surface.

17. Shape-selective catalysis :A catalytic reaction that depends upon the pore structureof catalyst as well as the size of reactant & product molecules is called Shape-selecticatalysis.

18. Enzyme Catalysis :Enzymes are biological catalyst which catalyse specific

biochemical reactions. They are complex nitrogenous organic compounds which a produced by living plants and animals having high molecular mass. They are highly effic because they increase the rate of reaction by 108 to 1020 times.

Eg. 23222 2 CO NH O H CONH NH Urease + +

Urease is an enzyme used for the decomposition of Urea only.

19. Colloids or Colloidal Solution :A heterogeneous solution in which dispersed phase mixed in dispersion medium.

20. Lyophilic Colloids :Those colloids which are solvents loving or attracting they arereversible Sols.21. Lyophobic Colloids :- Those colloids which are solvent hating. It isirreversible Sols.

22. Multimolecular Colloids:A colloid in which large no. of atoms or smaller molecules aggregate together to form species having size in colloidal range for eg. A sulpsol consists of particles containing about a thousand of S8 molecule.

23. Macromolecular colloids :A colloid in which the size of dispersed particles are ina colloidal range. Such dispersed phase in dispersion medium is called Macromolecucolloids. For Eg. Proteins, Starch and Cellulose form macromolecular colloids.24. Associated Colloids :Those colloids which behave as strong electrolyte at lowconcentration but at high concentration behave like colloids due to formation of aggrega particle of colloidal dimensions. For eg. Micelles are associated colloids.

25. Kraft Temperature :The formation of Micelles takes place only above a particular temp. is called Kraft temp.

26. Peptization :The process of converting precipitate into colloidal sol by mixingsmall amount of electrolyte into dispersion medium known as peptization and the electroknown as peptizing agent.

27. Dialysis : It is the process of purification of colloids by diffusion through a semi permeable membrane.

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28. Ultra filtration: It is the process of separating the colloidal particles from thesolvent and the solute present in colloida solution by ultra filter paper.

29. Tyndal effect : The process of scattering of light in colloidal solution bycolloidal solute known as Tyndal effect. The bright cone of light is called Tyndal cone.

30. Brownian Movement : The continuous zig zag motion of dispersed phase in dispersion medium is called Brownian Movement. It is due to the unbalanc bombardment of the particles by the molecules of the dispersion medium.

31. Helmholtz Electrical double layer : The combination of the two layers of opposite charges around the colloidal solute is called Helmholtz Electrical double layWhen the colloidal particles acquire +ve or ve charge by selective adsorption of one ofions, It attracts counter ions from the medium forming a second layer like.

Ag I / I- K + AgI / Ag+ I

32. Zeta potential or Electro kinetic potential : The potential difference between

the fixed layer and the diffused layer of colloidal solution having opposite charges.33. Electrophoresis : The process of migration of charged colloidal solute towardsthe oppositely charged electrode in colloidal solution is known as Electrophoresis.

34. Coagulation :The process of converting colloidal solution into precipitate by mixingsmall amount of oppositely charged electrolyte known as Coagulation.

35. Coagulative Value :The minimum no. of a milli moles of electrolyte requires tocoagulate one litre colloidal solutions.

36. Hardy-Schultz Rules: It has two rules :a) Oppositely charged ions are effective for coagulation. b) The coagulative power of electrolyte increases with increase in charged on th

ion used for coagulation. For Eg. :Al3+> Ca++> Na+ for negatively charged colloids. Similarly[ Fe(CN)6]4- > PO43- >SO42- > Cl- for positively charged colloids.

37. Emulsion : A colloids contain dispersed phase and dispersion medium both inliquid state is known as Emulsion.

There are two types of emulsion.(i) Oil in water & (ii) water in oil.

38. Cottrell Smoke precipitator : Smoke is a colloidal solution of solid particleslike C, As compounds and dust in air. It comes out through the chimneys of industrial plaIt consists of two metal discs charged to high potential. The charged dust and C , As partiget discharged towards oppositely charged metal disc in form of precipitate while gases coout through chimney.

1 MARK QUESTIONS

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Q. 1. What kind of adsorption is represented by the following graph :

T

x

M

Ans. Chemisorption.

Q. 2. In the titration of oxalic acid by acidified KMnO4, the oxidation of oxalic acid isslow in the beginning but becomes fast as the reaction progresses. Why ?

Ans. Autocatalysis by Mn+2.

Q. 3. Out of PO43,, SO42,, Cl ,, which wil act as the best coagulating agent for for Fe(OH)3 ?

Ans. PO43 .

Q. 4. Arrange the following in correct order of their coagulating power :

Na+, Al3+, Ba2+

Ans. Na+ < Ba2+ < Al3+

Q. 5. Which type of charged particles are adsorbed on the surface of As2S3 during itspreparation ?As2O3 + 3 H2S As2S3 + 3 HOH

Ans. S2

.Q. 6. Which type of metals act as effective catalysts ?

Ans. Transition metals.

Q. 7. The colloidal solution of gold prepared by different methods have differentcolours. Why ?

Ans. Due to difference in th

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