CBSE Sample paper class XII CHEMISTRY 2008 1


Sample Paper – 2008

Class – XII

Subject - Chemistry

(Kinetics, Solid, Solutions and Electro)

Q1. Identify the reaction order from each of the rate constants is k = 2.3 × 10–5 L mol-1 s-1. 1 mark

Q2. (a)What advantage the osmotic pressure method has over elevation in boiling point method for determining molecular mass? 1 mark (b) Arrange the following in increasing order of freezing points; 1 mark

1M NaCl, 1M glucose, 1M CaCl2

Q3 (a) Atoms of element B form hcp lattice and those of the element A occupy 2/3rd of tetrahedral voids. What is the formula of the compound formed by the elements A and B? 1 mark

(b) Under what conditions could quartz be converted into glass? 1 mark

Q4. Discuss positive deviation from Raoult’s law with suitable example? 3 marks

Q5. (a) Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example. 2 marks

(b)Write two differences between Frenkel defect and Schottky defect 1 mark

Q6. How many grams of KCl should be added to 2 Kg of water to lower the freezing point to minus 8 0C? Kf (water) = 1.86 0C kg mole -1

Or

An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling point of the solvent. What is the molar mass of the solute? 3 marks

Q7. An element with molar mass 2.7×10-2 kg mol-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7×103 kg m-3, what is the nature of the cubic unit cell? 3 marks

Q8. Resistance of a conductivity cell filled with 0.1 mol L–1 KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 mol L–1 KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 mol L–1 KCl solution. The conductivity of 0.1 mol L–1 KCl solution is 1.29 S/m. 3 marks

Q9. Calculate the e.m.f of cell reaction Cr (s)| Cr3+(0.001 M) || Fe 2+ (0.001 M)| Fe(s)

given [ E0 (Fe2+ / Fe ) = _ 0.44 V and E0 (Cr3+ / Cr ) = _ 0.74 V ] 3 marks

Q10. A reaction is first order in A and second order in B. 3 marks

(i) Write the differential rate equation.

(ii) How is the rate affected on increasing volume of container two times?

(iii) How is the rate affected when the concentrations of both A and B are doubled?

Q11. For the decomposition of azoisopropane to hexane and nitrogen at 543 K, the following data are obtained.

t (sec)

P(mm of Hg)

0

35.0

360

54.0

Calculate the rate constant. 3 marks

Q12. (i) Write anodic and cathodic reactions taking place in Mercury cell. 2 marks

(ii) For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction. 2 marks

(iii) ZnO becomes yellow on heating. Why? 1 mark

Q13. Predict & write reactions at cathode and ande when 2 marks

(i) AgNo3 solution is electrolysed using Pt electrodes.

(ii)CuSO4(aq) solution is electrolysed using copper electrodes (aq)

Q13. Caesium chloride crystallises as a body centred cubic lattice and has a density of 4.0 g cm-3. Calculate the length of the edge of the unit cell of caesium chloride crystal. (Moleculer mass of CsCl = 168.5 g mol-', NA = 6.02 x 1023 mol-'].

3marks

Q14. Explain giving suitable reasons: 3 marks

    1. Rusting of iron is quicker in saline water than in ordinary water.
    2. Iron does not rust even if zinc coating is broken in a galvanised iron pipe.
    3. It is not possible to determine λm for weak electrolytes graphically.

Q15. A galvanic cell consists of a metallic zinc plate immersed in 0.1M Zn(NO3)2 and metallic plate of lead in 0.2M Pb(NO3)2 solution. Calculate the emf of cell.

Given E0 Zn2+ │ Zn = -0.76V & 3 marks

E0Pb2+ │Pb= -0.13V.

 

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