HILLOCK INTERNATIONAL SCHOOLSIRUMALAIClass VII

Marks 30I. Fill in the blanks:

4x1=41. The rearing of silkworms for obtaining silk is called _______________

2. _____________ leaves are eaten by silkworms.

3. _____________ is extracted from lichens.

4. Properties such as shape, size, colour and state of a substance are called its _______________ properties.

II. Match the following:

5x1=51. Scouring

|Metal

2. Mulberry leaves|Base

3. Yak

|Wool yielding animal

4. Sodium hydroxide|Food of silkworm

5. Copper

|Cleaning sheared skin

III. Answer the following questions:

4x1=41. Name the most common Silkmoth.

2. Which solution is applied on the skin when an ant bites

3. What is the chemical name of baking soda

4. Burning of coal is a physical change or chemical change?

IV. Answer any three questions:

3x2=61. Why rusting of iron objects is faster in coastal areas than in deserts

2. Explain why an antacid tablet is taken when you suffer from acidity

3. Is distilled water acidic/basic/neutral? How would you verify it?

4. What is mean by the term rearing?

5. What is meant by the white fleece of the lamb

V. Answer any 2 questions:

2x3=61. Describe the process of neutralization with an example2. State any 3 differences between acids and bases

3. Classify the changes involved in the following processes as physical or chemical changes

a. Melting of wax

b. Digestion of food

c. Beating aluminium to make aluminium foil

4. Complete the following using appropriate wordsa. Silk fibres are made of ___________

b. Weavers weave silk threads into _________

c. Mostly, sheep are reared for getting ______________

VI. Answer any one question:

1x5=51. Draw the life cycle of silk worm

2. Describe how crystals of copper sulphate are prepared

HILLOCK INTERNATIONAL SCHOOL

SIRUMALAIClass VII

Marks 30I. Fill in the blanks:

4x1=41. Like synthetic fibres, plastic is also a ____________2. Synthetic fibres are synthesized form raw material called___________

3. Metals react with acids to produce ______________ gas.

4. Least polluting fuel for vehile is _____________.

II. Match the following:

5x1=51. Coke

|Jewellery

2. Gold

|Machinery

3. Iron

|carbon

4. Rayon

|Do not wrinkle

5. Polyester|Artifical silk

III. Answer the following questions:

4x1=41. Give an example for synthetic fibres

2. Why plastic containers are favoured for storing food

3. Why aluminium foils are used to wrap food items

4. Name the petroleum product used for surfacing roads

IV. Answer any three questions

3x2=61. Write any two uses of coke

2. Sodium and potassium are stored in kerosene. Give reason

3. Write word equation of the reaction involved when nails are placed in copper sulphate solution

4. Give examples which indicate that nylon fibres are very strong.

5. Explain why some fibres are called synthetic

V. Answer any two questions:

2x3=61. Explain the difference between thermoplastics and thermosetting plastics.

2. Write any 3 uses of metals

3. Can you store lemon pickle in an aluminium utensil? Explain.

4. Describe how coal is formed from dead vegetation. What is this process called?

VI. Answer any one questions:

5x1=51. Distinguish between Metals and Non-Metals.2. Avoid plastics as far as possible. Comment on this advise.

Marking Scheme

Class :VII

Subject: Science-ChemistryQ.NOANSWERSMARKS

I.1Sericulture1

2Mulberry1

3Litmus1

4Physical1

II1Cleaning sheared skin1

2Food of silk worm1

3Wool yielding animal1

4Base1

5Metal1

III1Mulberry silk moth1

2Calamine1

3Sodium bi carbonate1

4Chemical change1

IV1In coastal areas content of moisture in air is high as compared to desert regions, rusting becomes faster2

2An antacid tablet consists of a base like milk of Magnesia. It neutralizes the effect of excessive acid and brings relief.2

3Distilled water is neutral by nature. We can verify by performing litmus paper test. It neither turns blue litmus into red. Nor it turns red litmus into blue.2

4It is raising and taking care of live stock for commercial purposes.2

5White fleece of lamb means the colour of the fleece of lamb is white. The natural fleece of sheep and goats is black, brown or white.2

V1a. Protein

b. Silkcloth

c. Wool1

1

1

2The reaction between an acid and a base is known as neutralization. Salt and water are produced in this process with the evolution of heat.

Acid+Base --------------( salt+water

3

3AcidBase1

1

1

1. Sour in tasteBitter in taste

2. Turns blue litmus into redTurns red litmus into blue

3. Eg. Acetic acid, citric acidEg. Sodium hydroxide, potassium hydroxide

4a. Physical change

b. Chemical change

c. Physical change1

1

1

V1

21. Take a cupful of water in beaker and add a few drops of dil. Sulphuric acid.2. Heat the water. When it starts boiling add copper sulphate powder slowly while stirring continuously.

3. Filter the solution. Allow it cool.

4. Do not disturb the solution when it is cooling.

5. You can see the crystals of copper sulphate after few hours11

1

1

1

Marking Scheme

Class :VIII

Subject: Science-Chemistry

Q. NOANSWERSMARKS

I.1Polymer1

2Petrochemicals1

3Hydrogen 1

4CNG1

II1Carbon1

2Jewellery1

3Machinery1

4Artificial silk1

5Do not wrinkle1

III1Rayon, nylon1

2Light, strong, durable and cheap1

3Because it is highly malleable.1

4Coal tar1

IV1It is used in the manufacture of steelIt is used to make fuel gases2

2Sodium and potassium are highly reactive elements. They can easily catch fire even when they come in contact with air. So, they have to be kept in kerosene.2

3Iron + copper sulphate-----( iron sulphate + copper2

4Nylon is a very strong fibre that is why nylon is used for making parachutes, rock climbing ropes, fishing nets, seat belts etc., A nylon thread is actually stronger than a steel wire.2

5Some fibres are called synthetic because they are not made from natural fibres. Eg. Rayon nylon and acrylon2

V1ThermoplasticsThermosetting plastics1

1

1

1. Plastics which can be deformed and bend easily are known as thermoplasticsPlastics which when moulded once cannot be bent and deformed on heating are known as thermosetting plastics

2. They are used for making toys, containers, etcThey are used for making switches, handles of utensils, floor tiles etc.,

3. Example : PVC, PolytheneBakelite and Melamine

2Metals are used in the following1. Machinery

2. Cooking utensils

3. Electrical wires

4. Ships , trains

5. Construction material 3

3No, we cannot store lemon pickle in aluminium utensils, as metals react with acids to liberate hydrogen gas. The pickle can be spoiled3

4Due to natural processes the forests got buried under the soil. The plants got converted into coal. The process of conversion of dead vegetation into coal is called carbonization. It is also known as fossil fuel.3

VI1PropertiesMetalsNon-Metals1

1

1

1

1

1. AppearanceLustrousDull

2. HardnessHardSoft

3. MalleablilityMalleableNot malleable

4. DuctilityDuctileNot ductile

5. ConductivityGood conductorsBad conductors

21. Plastics are non-biodegradable and take a lot of time to decompose.

2. Plastics are not eco-friendly.

3. The plastic left in the soil results in soil pollution

4. Plastic bags drained into the water bodies cause threat to the aquatic life also

5. Polybags choke the drains and sewage piper thus causing lot of trouble.11

1

1

1

HILLOCK INTERNATIONAL SCHOOL

SIRUMALAIClass XI

Marks 70

I. Answer all the questions:

20x1=201. What is limiting reagent?

2. What do mean by Mole fraction?

3. Calculate the formula mass calcium chloride.

4. Define one mole?

5. Which of the following orbitals are not possible? 1p, 2s, 3f and 4d

6. Write the electronic configuration of the element having atomic number 24.

7. What is the relationship between frequency and wavelength of light?

8. State Pauli Exclusion Principle. 9. State the modern periodic law. 10. Define atomic radius.

11. What the elements of a group have common among them?

12. What the s- and p- block elements are collectively called?

13. What is meant by disproportionation?

14. What is galvanization?

15. Identify the central atom in the following and predict their Oxidation state

16. Name the constituents of water gas.

17. Name one compound each in which hydrogen exists in (i) positive oxidation state, and (ii) Negative oxidation state.

18. What is meant by 10 volume hydrogen peroxide?

19. Why is dihydrogen gas not preferred in balloons?

20. Out of Zn and Cu which is more reactive?

II. Answer the following questions:

5x2=101. Define the law of multiple proportions. Explain it with one example.

2. Mention the draw backs of Rutherfords atomic model.

3. Describe the two merits of long form periodic table over the Mendeleevs periodic table?

4. Determine the oxidation no. of all the atoms in the following oxidants:KMnO4, K2Cr2O7 and KClO4 5. What causes the temporary and permanent hardness of water?

III. Answer the following questions:

5x3=15

1. What is the percentage of carbon, hydrogen and oxygen in ethanol?

2. Write the 3 points of difference between orbit and orbital.

3. Why does the first ionization enthalpy increase as we go from left to right through a given period of the periodic table?4. Identify the oxidizing and reducing agents in the following equations:

(i) Fe + H2SO4FeSO4 + H2 (ii) H2 + Cl2 2HCl (iii) MnO2 + 4HClMnCl2 + 2H2O + Cl2 5. Hard water is unsuitable for laundry, washing and dyeing. Explain

IV. Answer the following:

5x5=25

1. What is the difference between empirical and molecular formula? A compound contains 4.07 % hydrogen, 24.27 % carbon and 71.65 % chlorine. Its molar mass is 98.96 g. What are its empirical and molecular formulas?

2. What are the draw backs of Bohrs atomic model? Show that the circumference of the Bohr orbit for the hydrogen atom is an integral multiple of the de Broglie wavelength associated with the electron revolving around the orbit.

3. What is the cause of the periodicity in the properties of the elements? How do the following properties vary in (a) a group and (b)in a period (i) electro negativity (ii) ionization enthalpy (iii) Atomic size

4. What is SHE? What is its use?5. What do you understand by (i) electron-deficient, (ii) electron-precise, and (iii) electron-rich compounds of hydrogen? Provide justification with suitable examples.

Marking Scheme

Class :XI

Subject:Chemistry

Q.NOAnswersMarks

I1The reactant which gets consumed first or limits the amount of product formed is known as limiting reagent1

2One mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of the carbon-12.1

3 Formula mass of CaCl2= 40+2 x35.5=40+71 = 111 u1

4Mole Fraction is the ratio of number of moles of one component to the total number of moles (solute and solvents) present in the solution. It is expressed as 'x'.1

51p and 3f are not possible.1

61s2 2s2 2p6 3s2 3p6 3d5 4s11

7velocity of light = frequency x wavelength. Frequency and wavelength are inversely proportional to each other.1

8No two electrons in an atom can have the same set of four quantum numbers or an orbital can have maximum two electrons and these must have opposite spin.1

9- The physical and chemical properties of the elements are the periodic function of their atomic numbers.1

10The one-half the distance between the nuclei of two covalently bonded atoms of the same element in a molecule is called as atomic radius.1

11They have same number of electrons in the valence shell.1

12Representative elements.1

13In a disproportionation reaction an element simultaneously oxidized and reduced. P4 + 3OH- +3H2O PH3 +3H2PO2-1

14Coating of a less reactive metal with a more reactive metal e.g.- coating of iron surface with Zn to prevent rusting of iron.1

15central atom:- N; O.S. +5 1

16Zn1

17Carbon monoxide and hydrogen1

18(i) HCl (ii) NaH1

19It means that 1 ml of H2O2 will give 10 ml of oxygen at N.T.P. 1

20Dihydrogen gas is combustible in nature. Therefore, it may react with oxygen highly violently. Thus, it is not used in balloons. 1

II1When two elements combine to form two or more compounds, then the different masses of one element, which combine with a fixed mass of the other, bear a simple ratio to one another. For example- carbon combines with oxygen to form two compounds CO and CO2. Compound CO CO2 Mass of C 12 12 Mass of O 16 32 Masses of oxygen which combine with a fixed mass of carbon (12g) bear a simple ratio of 16:32 or 1:2.2

21.It could not explain the stability of an atom.

2. It could not explain the line spectrum of H- atom.2

31. It removed the anomalies about the position of isotopes which existed in the Mendeleevs table.

2. It relates the position of an element in the periodic table with its electronic configuration.2

4In KMnO4 K = +1, Mn = +7, O = -2 In K2Cr2O7K = +1, Cr = +6, O = -2 In KClO4K = +1, Cl = =+7, O = -22

5Temporary hardness is due to presence of soluble bicarbonates of calcium and magnesium. On the other hand, permanent hardness is due to presence of chlorides and sulphates of calcium and magnesium. 2

III1Molecular formula of ethanol is : C2H5OH Molar mass of ethanol is : (212.01 + 61.008 + 16.00) g = 46.068 g Mass per cent of carbon = (24.02g / 46.068g) 100 = 52.14% Mass per cent of hydrogen = (6.048g / 46.068g)100 = 13.13% Mass per cent of oxygen = (16.00 g / 46.068g)100 = 34.73%3

2Ans. Orbit orbital 3

1. An orbit is a well defined circular path around the nucleus in which the electrons revolve 1. An orbital is the three dimensional space around the nucleus within which the probability of finding an electron is maximum(upto 90 %)

2. It represents the planar motion of an electron around the nucleus 2. It represents the three dimensional motion of an electron around the nucleus

3. All orbits are circular and disc like

3. Different orbitals have different shapes, i.e., s-orbitals are spherically symmetrical, p-orbitals are dumb-bell shaped and so on.

3In a period, the nuclear charge (the number of protons) increases on going from left to right. The electron added to each element from left to right enters the same shell. This results in an increase of the effective nuclear charge across the period on moving from left to right. As a result, the electron get more firmly bound to the nucleus. This causes an increase in the first ionisation enthalpy across the period.3

4:(i) O.A. =H2SO4 ; R.A.= Fe (ii) O.A. = Cl2; R.A.=H2 (iii)O.A. = MnO2; R.A. =HCl3

5since we know that the soap are the sodium salts of higher fatty acids like stearic acid (C17H35COOH), oleic acid (C17H33COOH) or palmitic acid (C17H31COOH). When soap is added to hard water, the anions of soap combine with Ca+2 and Mg+2 ions to form calcium and magnesium salt which are insoluble in water.

M+2 + 2C17H35COONa (C17H35COO)2M + 2Na

From hard sodium stearate Metal stearate

Water (Soap) (precipitate)

Therefore, no lather is produce until all the calcium and magnesium ions are precipitated. This also results into wastage of lot of soap. So hard water is unsuitable for laundry, washing and dyeing

3

IV1A compound contains 4.07 % hydrogen, 24.27 % carbon and 71.65 % chlorine. Its molar mass is 98.96 g. What are its empirical and molecular formulas? Ans. An empirical formula represents the simplest whole number ration of various atoms present in a compound whereas the molecular formula shows the exact number of different types of atoms present in a molecule of a compound.

The empirical formula of the above compound is CH2Cl. empirical formula mass is 12 + (1x2) + 35.5 = 49.5 n= molecular mass/ empirical formula mass =98.96/49.5 = 2 Hence molecular formula is C2H4Cl2

5

2.1.Bohrs model failed to account for the finer details of the hydrogen spectrum.

2. Bohrs model was also unable to explain spectrum of atoms containing more than one electron.

3. Bohrs model was unable to explain Zeeman effect and Stark effect i

4. Bohrs model could not explain the ability of atoms to form molecules by chemical bonds

Since a hydrogen atom has only one electron, according to Bohrs postulate, the angular momentum of that electron is given by:

Where, n = 1, 2, 3, According to de Broglies equation:

Substituting the value of mv from expression (2) in expression (1):

Since2rrepresents the circumference of the Bohr orbit (r), it is proved by equation (3) that the circumference of the Bohr orbit of the hydrogen atom is an integral multiple of de Broglies wavelength associated with the electron revolving around the orbit.5

3It is due to the similarity in the outer electronic configurations which gives rise to the periodic properties of the elements.

(a) In a group:

(i) Electronegativity- It decreases down the group.

(ii) Ionisation enthalpy- It decreases down the group.

(iii) Atomic size- It increases down the group.

(b) In a period:

(i) Electronegativity- Increases

(ii) Ionisation enthalpy- Increases

(iii) Atomic size- Dereases. 5

4Standard Hydrogen Electrode (SHE) has beenselected to have zero standard potential at alltemperatures. It consists of a platinum foilcoated with platinum black (finely dividedplatinum) dipping partially into an aqueous solution in which the activity (approximateconcentration 1M) of hydrogen ion is unity andhydrogen gas is bubbled through the solutionat 1 bar pressure.The potential of the other half cell is measuredby constructing a cell in which reference electrode is standard hydrogen electrode. The potential of the other half cell is equal to thepotential of the cell.

5

5[a]Electron deficient:- The hydrides which do not have sufficient number of electrons to form normal covalent bonds is called electron deficient hydride. For example, hydride of group 13 (BH3, AlH3, etc.).

[b] Electron precise:-The hydrides which have sufficient number of electrons required for forming covalent bonds is called electron precise hydride. For

example, hydrides of group 14 (CH4, SiH4, GeH4, SnH4, PbH4 etc.) they have tetrahedral geometry.

[c] Electron rich hydrides:-The hydrides which have excess electrons as required to form normal covalent bonds is called electron rich hydride. For example, hydrides of group 15 to 17 (NH3, PH3, H2O, H2S, H2Se, H2Te, HF etc.)5

HILLOCK INTERNATIONAL SCHOOL

SIRUMALAIClass XII

Marks 70

I. Answer all the questions:

1. Name one zero order reaction.2. What is the effect of temperature on the rate constant of a reaction?3. In a pseudo first order hydrolysis of ester in water, the following results were obtained:t/s 0 30 60 90

[Ester]mol L1 0.55 0.31 0.17 0.085

Calculate the average rate of reaction between the time interval 30 to 60 seconds4. Define the term colligative properties?5. What are the possible deviations from ideal behaviors? 6. Define the term azeotrope?7. Define 'electrophoresis'8. What is an emulsion? 9. what causes Brownian movement in a colloidal solution? (1)

10. Write the elements of group 15? 11. Write two uses of dinitrogen.12. What happens when red blood cells are placed in 0.1% NaCl solution? II answer all the questions:

1. A reaction is second order with respect to a reactant. How is the rate of the reaction affected if the concentration of the reactant is i) doubled ii) reduced to

2. A first order reaction is 15% complete in 20 minutes. How long it take to be 60% complete.3. Describe the following:( 2)

(i) Tyndall effect

(ii) Shape-selective catalysis

4. What is meant by coagulation of a colloidal solution? Name any method by which coagulation of lyophobic sols can be carried out. (2)5 Plot a graph between vapour pressure and mole fraction of a solution obeying Raoults Law at constant temperature? [2]

6 Draw the graphs of both deviations from ideal behaviours? [2]

7 When 20g of a non volatile solid is added to 250 ml of water, the freezing

point of water becomes -0.90C. Calculate molecular mass of the solid if kf of water is 1.860Ckg/mol. [2]

III answer all questions:1. The vapour pressure of CS2at 5000C is 854 mm Hg .A solution of 2.0g sulphur in 100g of CS2 has a vapour pressure of 848.9 mm Hg .Calculate the formula of sulphur molecule. [3]

6. What is the difference between multi molecular and macromolecular colloids? Give example of each type. How are associated colloids different from these two types of col1oids ? (3)

7. Define each of the following terms: (3)

(i) Micelles

(ii) Peptization

(iii) Desorption

IV answer all questions

1. (a) State Henry's law and mention its two applications.

(b) State Raoult's law for the solutions containing nonvolatile solute.

(c) On dissolving 19.5 g of CH2FCOOH in 500 g of water a depression of 10C in freezing point of water is observed. Calculate the Vant Hoff factor. Given Kf = 1.86 K Kg mol-1.2. a. Explain what is observed when (3)

(i) An electric current is passed through a sol

(ii) A beam of light is passed through a sol

(iii) An electrolyte (say NaCl) is added to ferric hydroxide solb. Write any two features which distinguish physisorption from chemisorption.Marking Scheme

Class :XI

Subject:Chemistry

Q.NOAnswersMarks

I11

2The rate constant is nearly doubled with a rise in temperature by 10 for a chemical reaction.

3Average rate of reaction between the time interval, 30 to 60 seconds, = 4.67 103 mol L1 s1

4The properties which depends upon amount of solute and not upon the nature of soluteare called colligative properties.

5There are two types of deviation from ideal behaviour positive and negative deviations.

6A solution at certain concentration when continues to boil at constant temperature without change in its composition in solution & in vapour phase is called an azeotrope.

7Themovement of colloidal particles under an applied electric potential towards oppositely charged electrodes is called electrophoresis.

8Emulsions are liquid-liquid colloidal systems

9Due to unbalanced bombardment of the colloidal particles by the molecules of the dispersion medium.

10The elements of group 15 are Nitrogen (N), Phosphorous (P) , Arsenic (As) , Antimony (Sb) and Bismuth (Bi).

11

12

II1 Rate = K [A]2

(i) When concentration of reactant is doubled the rate becomes 4 times.

(ii) When concentration of reactant is reduced to the rate becomes times.

2

3Tyndall Effect:- The scattering of light by the colloidal particles present in a colloidal sol is called Tyndall effect 1 + 1

Shape Selective Catalysis:- The catalytic reaction that depends upon the pore structure of the catalyst and the size of the reactant and product molecules is called shape-selective catalysis.11

4Coagulation is a process of aggregating together the colloidal particles so as to change them into large particles which ultimately settle as a precipitate.

By electrophoresis, coagulation of lyophobic Sols can be carried out / or any other method.

11

5

6

7

6Multimolecular colloids Macromolecular colloids

They are aggregates of molecules They themselves are large molecules

less than 1nm thick. of colloidal dimensions

Example :Sulphur Sol Example :Starch

Associated colloids are those which at low concentration behave as normal electolytes

& at high concentration act as colloids.

11

1

7i) Micelles:

Micelles are associated colloids which show colloidal behaviour at high

concentration and act as strong electrolytes at lowconcentration.

ii) Peptization:

The process of converting a precipitate into colloidal sol by shaking itwith

dispersionmediumin the presence of a small amount of electrolyte is called

Peptization.

iii) Desorption:

The process of removing an adsorbed substance froma surface onwhich it is adsorbed is called desorption.11

1

IV1a.

b.

2

1

2

2Electrophoresis takes place when sol particles move towards opposite

electrodes due to attraction.

ii) Tyndall effect will be observed due to scattering of light by colloidal

particles.

iii) Coagulation takes place (due to neutralisation of charges.)

b.