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KVS(KOL)CHEM/PBCHEM/PBCHEM/PBCHEM/PB----3333

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KENDRIYA VIDYALAYA KENDRIYA VIDYALAYA KENDRIYA VIDYALAYA KENDRIYA VIDYALAYA SANGATHANSANGATHANSANGATHANSANGATHAN KOLKATA REGIONKOLKATA REGIONKOLKATA REGIONKOLKATA REGION

3333RDRDRDRD PREBOARD EXAMINATION (2016PREBOARD EXAMINATION (2016PREBOARD EXAMINATION (2016PREBOARD EXAMINATION (2016----17)17)17)17)

CLASSCLASSCLASSCLASS----XII CHEMISTRY (Theory) XII CHEMISTRY (Theory) XII CHEMISTRY (Theory) XII CHEMISTRY (Theory)

Time allowed: 3 hours Maximum Marks: 70Time allowed: 3 hours Maximum Marks: 70Time allowed: 3 hours Maximum Marks: 70Time allowed: 3 hours Maximum Marks: 70

General InstructionsGeneral InstructionsGeneral InstructionsGeneral Instructions : : : :

1) All questions are compulsory.

2) Q. no. 1 to 5 are very short answer questions and carry 1 mark each.

3) Q. no. 6 to 10 are short answer questions and carry 2 marks each.

4) Q. no. 11 to 22 are also short answer questions and carry 3 marks each.

5) Q. no. 23 is a value based question and carry 4 marks.

6) Q. no. 24 to 26 are long answer questions and carry 5 marks each.

7) Use log tables if necessary, use of calculators is not allowed.

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Q.1. What type of solid is SiC ? 1

Q.2. Write the IUPAC name of the given compound 1

CH3CH(CH3)C(CH3)2CH(CH3)CH2OH

Q.3. Give the two factors which influence the adsoption of a gas on a solid surface. 1

Q.4. Why the bond angle of NH4+ is higher than NH3 ? 1

Q.5. Which of the following compound will undergo SN2 reaction faster and why ? 1

CH3-CH-CH2-CH2-Br and CH3-CH2-CH-CH2-Br

CH3 CH3


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Q.6. Explain the following 2

i) A solution of chloroform and acetone is an example of maximum boiling azeotrope. ii) Doctors advice people suffering from high blood pressure to take salt restricted diet. Q.7. Write the IUPAC name of the compound [Co (NH3)2(en)2 ]Cl3 and draw the possible

Geometrical isomers of the compound. 2

Q.8.State Kohlrausch law of independent migration of ions. Why does the conductivity of a

solution decrease with dilution?

OR

What are fuel cells ? Give one example. What are the advantages of fuel cells over other

Galvanic cells. 2

Q.9. Name the reagents used in the following reactions : 2

i) CH3- C-CH3 CH3-CH-CH3

O O OH

ii) C-Cl CHO

Q.10. Give reasons for the following

i) The atomic sizes of Zr and Hf are almost equal.

ii) Transition metals have high enthalpies of atomisation. 2

Q.11. 3.9 g of benzoic acid dissolved in 49 g benzene shows a depression of freezing point

of 1.62 K. Calculate the van`t Hoff factor and predict the nature of solute (associated or

dissociated).Given kf for benzene is 5.12 K Kg mol-1 3

Q.12. a) Explain with suitable equation how Glucose reacts with the following reagents

i) HI

ii) Acetic anhydride, Pyridine


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b) Why α-amino acids in aqueous solution exhibits amphoteric behaviour. 3

Q.13. An element occurs in BCC structure with cell edge of 288 pm. The density of the

element is 7.2 g cm-3. How many atoms of the element does 208 g of the element contain? 3

Q.14. a) Arrange the following compounds in order of their increasing boiling point

i) Bromomethane, Bromoform, Chloromethane, Dibromomethane.

ii) 1-Chloropropane, Isopropylchloride, 1-Chlorobutane.

b) Draw the structure of optical isomers of 2-butanol. 3

Q.15. a) Name the following

i) A transition metal that does not exhibit variable oxidation state.

ii) Ore used for preparation of potassium permanganate.

b) Complete the following reactions

i) MnO4 + C2O42- + H+

ii) Cr2O72- + I + H+ (1+2)

Q.16. a) Give the mechanism of acid catalysed dehydration of ethanol to form ethene.

b) Write the equation for Reimer-Tiemann reaction. (2+1)

Q.17. A Galvanic cell consists of a metallic zinc plate immersed in 0.1 M Zn(NO3)2 solution

and metallic plate of lead in 0.02 M Pb(NO3)2 solution. Calculate the emf of the cell. Write the

chemical equation for the electrode reactions and represent the cell.

(Given EO Zn2+/Zn = -0.76 V , EO Pb2+/Pb = -0.13 V) 3

Q.18. Answer the following questions

i) What happens when a freshly precipitated Fe(OH)3 sol is shaken with small

amount of FeCl3 ?

ii) Mention how physisorption and chemisorption varies with temperature.

iii) Why leather gets hardened when soaked in chromic salt solution ? 3

Q.19. What chemical principle is involved in choosing a reducing agent for getting the metal

from its ore in pyrometallurgy? Consider the metal oxides Al

choice of reducing agent in each case.

Account for the following:

i) The reduction of metal oxide is easier if the metal formed is in the luquid state at

the temperature of reduction.

ii) CO is used in the purification of Ni by Mond proces

iii) Zinc metal is used in the extraction of Silver.

Q.20. a) What kind of drug is aspirin? Give

b) Give an example of a substance that can act as a disinfectant or antibiotic

depending upon its concentration and also mention its concentrations.

c) Name two artificial sweeteners

Q.21. Complete the following reactions

i) CH3- C-CH3 CH

O

KVS(KOL)

chemical principle is involved in choosing a reducing agent for getting the metal

from its ore in pyrometallurgy? Consider the metal oxides Al2O3 and FeO and justify

agent in each case. (Refer Ellingham diagram below)

OR

The reduction of metal oxide is easier if the metal formed is in the luquid state at

the temperature of reduction.

CO is used in the purification of Ni by Mond process.

Zinc metal is used in the extraction of Silver.

What kind of drug is aspirin? Give its structural formula



artificial sweeteners.

Complete the following reactions

CH3MgBr, H3O+


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chemical principle is involved in choosing a reducing agent for getting the metal

and FeO and justify the

The reduction of metal oxide is easier if the metal formed is in the luquid state at

3



3


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ii) CH3COOH Cl2 , Red P

iii) CH3 CHO dil NaOH 3

Q.22. a) Compare the following complexes on the basis of Hybridisation, Magnetic moment

using Valence Bond theory:

[ Fe F6 ] 4- and [ Fe ( CN ) 6 ] 4-

b) Write the ionisation isomer of [ Co ( NH3 )5 SO4 ] Br and give one chemical test to

distinguish between them. 3

Q.23. At a sweet shop in Kolkata, Rohit bought some sweets. He requested the sales boy to

put the sweets in a polythene bag. The sales boy refused to do so, instead he kept the sweet

box in a paper bag. After reading the above passage, answer the following questions.

i) As a student of chemistry, why would you advocate the use paper bags instead of

polythene bags? Which value is promoted through the use of paper bag?

ii) Give example of (a) a non biodegradable polymer other than polythene

(b) a biodegradable polymer

and also give the name and structure of their monomers from which they are prepared.

4

Q.24.a) Write the rate law for a first order reaction. Justify that half life for a first order

reaction is independent of initial concentration of the reactant.

b) For a first order reaction show that the time required 99% completion is twice the

time required for the completion of 90%.

c) Give an example of pseudo first order reaction.

OR

a) For the reaction A B , the rate of reaction becomes twenty seven

times when the concentration of A is increased three times. What is the order of

the reaction?

b) The rate constant for a first order reaction is 60 S-1. How much time will it take to

reduce the initial concentration of the reactant to its 1/16th value.

c) Give one difference between order and molecularity. 5


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Q.25. a) Write balanced equation of the following

i) Complete Hydrolysis of XeF6.

ii) Disproportionation reaction of orthophosphorous acid in water.

b) Account for the following

i) All the P-Cl bonds in PCl5 are not equal.

ii) O3 is strongly oxidising.

c) Arrange the following species in order of increasing acidic character

HF,HCl,HBr,HI

OR

a) Compare between Cl2 and F2 on the basis of their electron gain enthalpy and

oxidising property with proper justification.

b) Complete the following reaction

i) PbS + O3

ii) P4 + NaOH(aq)

c) PCl5 in solid state behaves as ionic salt. Explain. 5

Q.26. a) Distinguish between following pairs of compound by means of chemical test

i) Aniline and N-methylaniline

ii) Aniline and ethanamine.

b) Complete the following reaction

i) C6H5N2Cl + H3PO2 + H2O

ii) C6H5NH2 + Br2 (aq)

c) Explain why methanamine is more basic than aniline.

OR

a) Identify A,B in each case

I) NH2

NaNO2,HCl(273K) A CuCN B

NH2

Ii) Conc.H2SO4 A Heat B


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b) Account for the following

i) Aromatic amines cannot be prepared by Gabriel Phthalimide process.

ii) Aniline can not undergo Fridel Craft reaction.

c) How do you convert Benzene into Aniline. 5

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