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12th Class Chemistry Sample Paper - 4

Chemistry (Theory)
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Time Allowed: 3 hours

Maximum Marks: 70

General Instructions:

(a) All questions are compulsory.

(b) Question numbers 1 to 5 are very short answer questions and carry 1 mark each.

(c) Question numbers. 6 to 10 are short answer questions and carry 2 marks each.

(d) Question numbers 11 to 22 are also short answer questions and carry 3 marks each.

(e) Question number 23 carries 4 marks.

(f) Question numbers. 24 to 26 are long answer questions and carry 5 marks each

1. An element occurs in the BCC structure. How many atoms are present in its unit cell?

2. Consider the following reaction:

2NO(g)+2H2(g)--->N2 (g) + 2H2O(g)

The rate law for this reaction is first order with respect to H2 and second order with respect to NO. Write the rate law for this reaction.

3. Name the defect that results in decrease of density in crystals.

4. Draw the wedge and dash formula of the simplest chiral alkane and alkyne.

5. Mention two properties of acetonitrile because of which it acts as good solvent.

6. What happens when:

(i) Orthophosphorus acid is heated?

(ii) XeF6undergoes complete hydrolysis?

7. Define insulators and semiconductors on the basis of the band model. In an element 3s band half filled. Will it be insulator conductor or semiconductor?

8. The freezing point of benzene decreases by 2.12 K when 2.5 g of benzoic acid (C6H5COOH) is dissolved in 25 g of benzene. If benzoic acid forms a dimer in benzene, calculate the van’t Hoff factor and the percentage association of benzoic acid. (Kf for benzene = 5.12 K kg mol-1)

9. Write the names of monomers of Bakelite. State whether Bakelite is a thermoplastic or a thermosetting plastic. Give reason for your answer.

10. The conductivity of 10-3 mol /L acetic acid at 250C is 4.1 × 10-5 S cm-1. Calculate its degree of dissociation, if Λm for acetic acid at 250C is 390.5 S cm2 mol-1.

11. What is mordant dye? Give one example. How is it applied to fabrics?

12. What is chemical name of aspirin? Write its three uses.

13. Give the IUPAC name of the product formed when:

(i) 2-Methyl-1-bromopropane is treated with sodium in the presence of dry ether.

(ii) 1- Methyl cyclohexene is treated with HI.

(iii) Chloroethane is treated with silver nitrite.

14. A compound is formed by the substitution of two chlorine atoms for two hydrogen atoms inpropane. Write the structures of the isomers possible. Give the IUPAC name of the isomer which can exhibit enantiomerism.

15. Which one of the following compounds will undergo faster hydrolysis reaction by SN1 mechanism? Justify your answer.

16. Describe how the following steps can be carried out?

(a) Recovery of Gold from leached gold metal complex.

(b) Conversion of Zirconium iodide to pure Zirconium.

(c) Formation of slag in the extraction of copper.

(Write the chemical equations also for the reactions involved)

17. Explain the use of the following:

(a) NaCN in Froth Floatation Method.

(b) Carbon monoxide in Mond process.

(c) Coke in the extraction of Zinc from Zinc Oxide.

18. Predict the products of the following reaction:

19. (i) Deficiency of which vitamin causes night-blindness?

(ii) Name the base that is found in nucleotide of RNA only.

(iii) Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose?

20. A metal complex having composition Cr(NH3)4Cl2Br has been isolated in two forms A and B. The form A reacts with AgNO3 to give a white precipitate readily soluble in dilute aqueous ammonia whereas B gives a pale yellow precipitate soluble in concentrated ammonia.

i. Write the formulae of isomers A and B.

ii. State the hybridisation of chromium in each of them.

iii. Calculate the magnetic moment (spin only value) of the isomer A

21. Explain the following:

i. A body centered cubic (BCC) element (atomic mass 60kg) has a cell edge of 300pm.What is its density?

ii.Define the forbidden zone in band model of bonding in metals.

22. Describe the following with suitable examples:

i. Preservatives

ii. Tranquilizers

iii. Hybrid propellants

23. Convert:

i. Phenol into ocresol.

ii. Calcium acetate into ethanol.

iii. Propanoic acid into 3-aminopropanoic acid.

24. (a) Explain the following:

i. Henry’s law about dissolution of a gas in a liquid.

ii. Boiling point elevation constant for a solvent.

(b) A solution of glycerol (C3H88O3) in water was prepared by dissolving some glycerol in 500g of water. This solution has a boiling point of 100.42°C. What mass of glycerol was dissolved to make this solution? (Kb for water = 0.512 K kg mol-1)


OR


(a) Complete the following reactions:

(b) Give simple chemical tests to distinguish between the following pairs of compounds:

i. Ethanal and Propanal

ii. Benzoic acid and phenol

25. (a) Complete the following chemical equations:

i. Cu + HNO3 (dilute) →

ii. XeF4 + O2F2

(b) Explain the following observations:

i. Phosphorus has greater tendency for catenation than nitrogen.

ii. Oxygen is a gas but sulphur a solid.

iii. The halogens are coloured. Why?


OR


(a) What inspired N.Bartlett for carrying out reaction between Xe and PtF6?

(b) Arrange the following in the order of property indicated against each set:

i. F2, I2, Br2, Cl2 (increasing bond dissociation enthalpy)

ii. NH3, AsH3, SbH3, BiH3, PH3 (Decreasing base strength)

(c) Complete the following equations:

i. Cl2 + NaOH(cold and dilute) →

ii. Fe3++SO2+H2O →

26. (a) Account for the following observations:

i. SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed

ii. Chlorine water is a powerful bleaching agent.

iii. Bi(V) is a stronger oxidising agent than Sb(V)

(b) What happens when:

i. White phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2.

ii. XeF6 undergoes partial hydrolysis.

(Give the chemical equations involved).


OR


(a) A cell is prepared by dipping a zinc rod in 1M zinc sulphate solution and a silver electrode in 1M silver nitrate solution. The standard electrode potential given:

What is the effect of increase in concentration of Zn2+ on the Ecell?

(b) Write the products of electrolysis of aqueous solution of NaCl with platinum electrodes.

(c) Calculate e.m.f. of the following cell at 298 K:

Write the overall cell reaction.

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