11.Sr_Chem.pdf

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BOARD OF INTERMEDIATE EDUCATIONSr. INTER CHEMISTRY MODEL PAPER

(English Medium)Time: 3 Hours (w.e.f. 2013 - 14) Max. Marks: 60

SECTION ANote: I. Very Short answer type questions.

II. Answer ALL THE QUESTIONS at one place in the same order.III. Each question carries 2 MARKS 10 2 = 20

1. What are 'Schottky defects' in crystalline solids?2. Calculate the 'spin only' magnetic moment of Fe+2(aq.) ion.3. Calculate the mole fraction of sodium hydroxide in 10% W/W NaOH solution.4. How is change in Gibbs energy (G) related to the emf (E) of a galvanic cell?5. What is the role of Cryolite in the extraction of aluminium?6. How do you distinguish between crystal lattice and unit cell?7. What is PHBV? How is it useful to man?8. Write the names and structures of the monomers of the following polymers.

(a) Bakelite and (b) Nylon 6, 69. Write the possible chain isomers of the compound having molecular

formula C4H9Br.10. How is ethane converted to bromoethane?

SECTION BNote: I. Short answer type questions.

II. Answers any SIX questions.III. Each question carries 4 MARKS 6 4 = 24

11. State Raoult's law. Calculate the vapour pressure of a solution containing 9 g ofglucose in 162 g of water at 293 K. The vapour pressure or water at 293 K is17.535 mm Hg.

12. What is Catalysis? What are the types of catalysis? Give one example for eachtype.

13. Differentiate roasting and calcination with examples?14. Explain the structures of a) XeF4 and b) XeOF4.15. Explain Werner's theory of coordination compounds with suitable examples.

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16. Give the sources of the following vitamins and name the diseases caused by thisdeficiency.a) A b) D c) E and d) K

17. Write short notes ona) Analgesics b) food preservatives

18. Explain Sand Meyer reaction and Carbyl Amine reactionSECTION C

Note: I. Long answer type questions.II. Answer any TWO questions.

III. Each question carries 8 MARKS. 2 8 = 1619. a) State and explain Kohlrausch's law of independent migration of ions.

b) What is order of a reaction? How is it different from the molecularity of areaction? Give one example each for first order and second order reactions.

20. a) How is Ozone prepared? How does Ozone reacts with i) PbS ii) Moist KI iii) Hg and iv) Ag ? Give equations.

b) Write the balanced equations for the following.i) NaCl is heated with conc. H2SO4 in the presence of MnO2.

ii) Chlorine is passed into a solution of NaI in water.21. a) Explain i) Cannizzaro reaction ii) Decarboxylation

b) Explain the acidic nature of phenols and compare it with that of alcohols.



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ANSWERSSECTION - A

1. What are "Schottky defects" in crystalline solids?Ans: A stoichiometric point defects that occurs due to missing of equal number of

cations and anions from their original lattice points, present in crystalline solidsare called schottky defects. e.g.: NaCl, CsCl.

2. Calculate the "spin only" magnetic moment of Fe+2 (aq.) ion?Ans: Fe = 26 = [Ar] 3d6 4s2 Fe+2 = [Ar]3d6

Magnetic moment () = n(n + 2). Where n = number of unpaired e = 4= 4(4 + 2)= 24 = 4.89 B.M.

3. Calculate the mole fraction of sodium hydroxide in 10% W/W NaOH solution.

Ans: n1 = number of moles of water = 90

18 = 5

n2 = number of moles of NaOH = 1040 = 0.25

n2 0.25 0.25 1X2 = mole fraction of NaOH = = = = = 0.0476

n1 + n2 5 + 0.25 5.25 21

4. How is change in Gibbs energy (G) related to the emf (E) of a galvanic cell?Ans: G = n F Ecell

where G = change in Gibbs energy

n = number of electrons

F = Faraday = 96487 C mol1

Ecell = emf of the cell.

5. What is the role of cryolite in the extraction of aluminium?

Ans: To dissolve alumina.

To increase electrical conductivity.

To decrease the melting point of alumina.



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6. How do you distinguish between crystal lattice and unit cell?

Ans: Crystal lattice: Regular three dimentional arrangement of points in space.

Unit Cell: The smallest basic three dimentional repeating unit from which

crystal lattice is built.7. What is PHBV? How is it useful to man?Ans: PHBV is poly - Hydroxy butyrate Co - Hydroxy valerate. It is a copolymer,

formed due to condensation of 3 - hydroxy butanoic acid and 3 - hydroxypentanoic acid. This biodegradable polymer is used for making capsules andorthopaedic devices.

8. Write the names and structures of the monomers of the following polymersa) Bakelite b) Nylon 6, 6

Ans: a) Bakelite:OH

O

Phenol: & Formaldehyde : H C H

b) Nylon 6, 6:Adipic acid: HOOC (CH2)4 COOH

Hexa methylene diamine: H2N (CH2)6 NH29. Write the possible isomers of the compound having molecular formula

C4H9Br.Ans: n-butyl bromide: CH3CH2CH2CH2Br

Secondary butyl Bromide: CH3 CH2 CH CH3Br

Tertiary butyl bromide: (CH3)3C Br10. How is ethane converted to bromoethane?Ans: When ethane is heated with bromine, bromoethane is formed due to free

radical bromination.Heat

C2H5 H + Br Br C2H5Br + HBr



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SECTION - B11. State Raoult's law. Calculate the vapour pressure of a solution containing

9 g of glucose in 162 g. of water at 293 K. The vapour pressure of water at293 K is 17.535 mm Hg.

Ans: The relative lowering of vapour pressure of a dilute solution of a non volatilesolute is equal to the mole fraction of the solute (X2).

p p = X2p

p = V.P. of pure solvent = 17.535 mm Hg.p = V.P. of solution = ?M1 = Molar mass of water (solvent) = 18 gM2 = Molar mass of glucose = 180 gw1 = Mass of solvent (water) = 126 gw2 = Mass of sloute (glucose) = 9 g

p p w2 M1 = p M2 w117.535 p 9 18 = 17.535 180 162

9 18 17.535p = V.P. of solution = 17.535

180 162= 17.535 0.0974= 17.438 mm Hg

12. What is catalysis? What are the types of catalysis? Give one example foreach type.

Ans: Small quantity of substances, which can alter the rate of a chemical reaction andthemselves remain chemically, quantitatively unchanged at the end of reactionare called catalysts and the phenomenon is called 'Catalysis'.Homogeneous Catalysis: The catalysis in which the reactants and catalyst are

in the same phase.NO (g)

2 SO2 (g) + O2 (g) 2 SO3HCl(l)

CH3COOC2H5 (l) + H2O (l) CH3COOH + C2H5OHHeterogeneous Catalysis: The catalysis in which the reactants and catalyst are in

different phases.Pt (s)

2 SO2 (g) + O2 (g) 2 SO3(g)Fe (s)N2(g) + 3 H2(g) 2 NH3(g)



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13. Differentiate roasting and calcination with examples.Ans: Roasting: The process of heating the ore strongly below its M.P. in presence of

air is called Roasting.Types of roasting:

a) Oxidising roasting: The type of roasting in which sulphide ore changes intooxide.

2 ZnS + 3 O2 2 ZnO + 2 SO2b) Sulphatizing roasting : The type of roasting in which sulphide ore changes

into sulphate.650C

ZnS + 2 O2 ZnSO4c) Chloridizing roasting: The type of roasting in which sulphide ore changes

into chloride.Calcination: The process of heating carbonate or bicorbonate ores below their

melting points in absence of air to give oxides (to remove volatile impurities).

ZnCO3 ZnO + CO2

2 NaHCO3 Na2CO3 + CO2 + H2O

14. Explain the structures of (a) XeF4 and (b) XeOF4.Ans: a) XeF4:

Xe = 5s25px25py15pz15d15d15d1 (2nd excited state)Xe undergoes sp3d2 hybridization. Due to presence of 2 lone pairs 4 bond pairs, in Xe, the shape of XeF4is square planar.

b) XeOF4:Xe = 5s25px15py15pz15d15d' 5d1 (3rd excited state)

Hybridization bondXe undergoes sp3d2 hybridization. Due to presence of one lone pair and 6 bond pairs (1 b.p. forms bond), the shape of XeOF4 is square pyramidal.

15. Explain Werner's theory of coordination compounds with suitable examples.Ans: Alfred Werner gave satisfactory explanation to the mechanism of formation of

complex. Some of the important postulates are: Every complex compound has central metal atom or ion. Central metal ion shows 2 types of valencies.



Xe

F F

FF

Xe

F O F

FF

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Primary Valence: It is equal to oxidation state of central metal atom. It is ionisable valence. It is non directional and represented by .... line. It is satisfied by -ve ions only.

Secondary Valence: It is equal to coordination number of central metal ion. It is satisfied by ligands. It is non ionisable valence. It is directional and represented by line. It is satisfied by -ve ions as well as neutral molecules.

16. Give the sources of the following vitamins and name the diseases caused bytheir deficiency.a) A b) D c) E d) K

S.No. Name of the Sources Deficiency diseasesVitamin

a Vitamin-A Carrot, Night Blindness,Fish oil Xerophthalmia

b Vitamin-D Egg Yolk, Rickets in Children,Sun Light Osteo- malacia in adults

c Vitamin-E Sun Flower oil, Sterility,Wheat germ oil Muscular weakness

d Vitamin-K Green leafy Haemorrhage, Vegetables, delay of blood clotting.Cabbage

H3N

H3N

Co+3

NH3Cl

ClCo+3

H3N

Cl

Cl

Cl

[Co(NH3)6] Cl3 [Co(NH3)5] Cl2

Ans:

NH3

NH3

NH3

NH3

Cl

NH3

H3N NH3

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17. Write short notes on

a) Analgesics and b) Food preservativesAns: a) Analgesics: The drugs which are used to reduce or relieve pain without

disturbing nervous system. There are 2 types of analgesies:

i) Narcotic analgesies: Analgesies having addictive property, that causedepression of central nervous system and relieves strong pains like cardiac

pain and post operative pains. e.g: Heroin, Morphine.

ii) Non-Narcotic Analgesics: Analgesics having no addictive property andrelieves mild aches like head ache, back ache etc. e.g.: Aspirin, Ibuprofen.

b) Food Preservatives: Chemicals which are added to preserve food by preventing spoilage of food due to microorganisms, to enhance appeal and to

increase the nutritive value.

e.g.: Common Salt, Sugar, Sodium Benzoate.

18. Explain (a) Sand Meyer reaction and (b) Carbyl amine reaction.Ans: (a) Sand Meyer reaction: The reaction in which diazonium group of diazonium

salt is replaced by the nucleophiles like Cl or Br or CN in presence of

Cu+ ion.e.g.: N2Cl Cl

HCl + N2Cu2Cl2

(b) Carbyl amine reaction: A dirty smelling compound Carbyl amine(Isocyanide) is formed when aliphatic or aromatic primary amine is heated

with Chloroform and ethanolic KOH.

NH2Heat

NC

e.g.: + CHCl3 + 3 KOH + 3 KCl + 3 H2O

(Alcoholic)



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SECTION - C19. (a) State and explain Kohlrausch's law of independent migration of ions.

(b) What is order of a reaction? How is it different from the molecularityof a reaction? Give one example each for first order and second orderreactions.

Ans: (a) Kohlrausch's law: The limiting molar conductivity of an electrolyte (m) isthe sum of the limiting molar conductivities of cation (+) and anion ().m = v+ + + V

Where V+ and V are the no. of cations and anions present in the electrolyte.e.g.: (1) m (NaCl) = Na+ + Cl

(2) m (BaCl2) = Ba+2 + 2 Cl(b) Order : The sum of the powers of the concentration terms of the reactants

present in rate determining step at a given temperature.

S.No. ORDER MOLECULARITY

1. The sum of the powers No. of species participating of the concentration terms in rate determining step.in rate equation.

2. It is determined It is determined theoritically experimentally. from reaction mechanism.

3. This can have values zero, This can not have values +ve, -ve or fractional. zero, -ve or fractional.

4. It is applicable to entire It is applicable to a part of the reaction. reaction.

Heat1st order reaction: e.g.: N2O5 2 NO2 +

12 O2

2nd order reaction: e.g.: CH3COOC2H5 + NaOH CH3COONa + C2H5OH

20. (a) How is ozone prepared? How does ozone reacts with (i) PbS (ii) Moist KI (iii) Hg and (iv) Ag.Give equations.(b) Write the balanced equations for the following.i) NaCl is heated with conc. H2SO4 in presence of MnO2.ii) Cl2 is passed into a solution of NaI in water.



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Ans: (a) By passing silent electric discharge through pure, dry, cold oxygen 10%ozone is formed. Pure O3 can be condensed in a vessel surrounded by liquidoxygen.

silent3 O2 2 O3; H = +142 K.J./molelectric discharge i) O3 oxidizes black PbS to white PbSO4.

PbS + 4 O3 PbSO4 + 4 O2ii) O3 oxidizes moist KI to I2.

2 KI + H2O + O3 I2 + O2 + 2 KOHiii) Hg loses lustre and meniscus and sticks to glass surface when reacts with

O3. This is called "tailing of mercury".2 Hg + O3 Hg2O + O2

iv) O3 oxidizes Ag to Ag2O.2 Ag + O3 Ag2O + O2

(b) (i) By heating NaCl with conc. H2SO4 & MnO2, chlorine gas is liberated.4 NaCl + MnO2 + 4 H2SO4 MnCl2 + 4 NaHSO4 + 2 H2O + Cl2

ii) Cl2 oxidizes NaI to I2.Cl2 + 2 Na I 2 NaCl + I2

21. (a) Explain i) Cannizzaro reaction and ii) Decarboxylation.(b) Explain the acidic nature of phenols and compare it with that of

alcohols.Ans: (a) i) Cannizzaro reaction: Aldehydes do not have alpha Hydrogens undergo

disproportionation on heating with strong alkali. Here aldehyde is oxidisedto salt of carboxylic acid & reduced to alcohol.H H

e.g.: C = O + C = O + Conc.KOH CH3OH + HCOOK

H Hii) Decarboxylation: The phenomenon of lose of CO2 from the sodium salt of

carboxylic acid when it is heated with soda lime (3 parts NaOH + 1part CaO)to form alkane.

CaOeg: CH3 COONa + NaO H CH4 + Na2CO3



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a.net(b) Acidic Nature of Phenols: Proton (H+) donor is acid -OH is electron withdrawing group and is attached to sp2 carbon of benzene ring. As

electronegativity of sp2 carbon of phenol, electron density decreases onoxygen. This will increase the polarity of O H bond and results increasein ionisation of phenols than that of alcohols. In alkoxide ion (RO), thenegative charge is localised only on oxygen, where as in phenol, negativecharge is deloclaised. Due to resonance, stable phenoxide ion is formed bylosing H+ ion easily.

.. ..

R O H R O: + H+.. ..

phenoxide ion is more stable than that of alkoxide ion. Acidity of phenolsis more than that of alcohols. When electron withdrawing groups like -NO2are attached to benzene in ortho, para positions in phenol, acidic nature willincreases further. From pka data we will understand that phenol is milliontimes more acidic than that of ethanol.

- A.N.S. SANKARA RAO, Senior Lecturer.



OH . .. O .. .

. .. O .. . . O .. .. O .. .

. O .. .. .. O .. .

+ H+

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11.Sr_Chem.pdf