CBSE Guess paper class XII Chemistry 2008 4


THE INDIAN SCHOOL, BAHRAIN

MODEL - I EXAMINATION (January 2007)

CHEMISTRY (Theory)

Class - XII

Marks 70

Time: 3 Hours

17 January 2007

Instructions

· Attempt ALL Questions.

· Electronic calculators are not allowed.

· Questions 1 to 5 carry 1 mark each.

· Questions 6 to 12 carry 2 marks each.

· Questions 13 to 24 carry 3 marks each.

· Questions 25 to 27 carry 5 marks each.

[1 - mark Questions]

1. Name two experiments or phenomena that support the wave nature of electrons.

2. Arrange the following orbitals in the increasing order of energy.

s*1s, 2s, s 1s, 1s

3. What is the percentage efficiency of packing in hcp structure. How do you rate the

efficiency of packing in body centred cubic structure with that in hcp?

4. State Henry’s law.

5. What is pseudo first order reaction?

[2 - mark Questions]

6. Account for the following:

(a) HF is a weaker acid than HCl.

(b) Na2HPO3 is neutral while Na2HPO4 is acidic.

7. The enthalpy of vaporisation of liquid ethoxyethane is 26.10 kJ mol-1at its boiling point

35.00 oC. Calculate the standard entropy change for the conversion of vapour to liquid

at the boiling point.

OR

The standard enthalpy of fusion (ΔfusHo) and standard entropy change (ΔfusSo) for the

melting of KCl are 7.25 kJ mol-1 and 7.00 J K-1 mol-1 respectively. Calculate the

melting point of KCl.

8. An aqueous solution of CuSO4 is electrolysed between platinum electrodes using a

current of 4 amperes for 30 minutes. What mass of copper is deposited at the cathode?

[Cu = 63.5 g mol-1; F=96500 C mol-1]

9. (a) Give the structure of the lowest possible alkane which has a chiral carbon atom.

(b) Account for the fact that meso compounds are optically inactive.

10. Write the structural formulae and names of the four possible products of aldol

condensation between ethanal and propanal.

11. Write the chemical equation to show the preparation of each of the following polymers.

(a) Neoprene

(b) Nylon-66

12. (a) What is meant by denaturation of protein?

(b) (i) What type of linkage is responsible for the formation of amylose from α-glucose?

(ii) Name the deficiency disease caused due to lack of vitamin E.

[3 - mark Questions]

13. The energy of the electron in hydrogen atom is – 2.18 x 10-18J per atom. If the electron

absorbs 1.938 x 10-18 J, what will be the principal quantum number of the electron in the excited state?

14. (a) If the radius of Li+ ion is 60 pm and that of F- is 136 pm, what are the coordination

numbers of Li+ ion and F- in LiF?

(b) In a metal iodide, every other octahedral hole in an hcp array of iodide ions is occupied

by the metal ion. What is the formula of the metal iodide?

15. (a) The osmotic pressure of blood is 7.75 bar at the body temperature 37 oC. What should be

the mass of glucose per litre for making an intravenous injection that is isotonic with

blood? [C6H12O6 = 180 g mol-1; R = 0.083 bar K-1 mol-1]

(b) Arrange the following liquids in the order of increasing boiling points:

0.15 m KI, 0.05 m AlCl3, water, 0.2 m CaCl2.

16. (a) Define the second law of thermodynamics.

(b) Find the value of equilibrium constant for the following reaction at 298 K.

2 NH3 (g) + CO2 (g) NH2 CO NH2 (aq) + H2O (l)

The standard Gibbs energy change, ΔrGo, at the given temperature is - 13.6 kJ mol-.

17. (a) Calculate the equilibrium constant for the cell reaction:

Ni (s) + Cu2+ (aq) Ni2+ (aq) + Cu (s) ; Eo = 0.59 V

(b) What is meant by the term ‘reduction potential’?

18. (a) What is rate law?

(b) For the reaction, A + 2B + C D2 + 2E ,

the experimentally determined order of the reaction is, Rate = [A] [B] [C]0.

What will be the rate of the reaction if the concentrations of all the reactants are tripled?

19. (a) Name two methods of purification of colloidal sols other than dialysis.

(b) What are heterogeneous catalysts? Give an example.

(c) Account for the fact that the extent of physisorption decreases with increase in

temperature.

OR

(a) Which one of the following electrolytes is most effective for the coagulation of

Fe(OH)3 sol and why? NaCl, Na2SO4, Na3PO4

(b) Which will be absorbed more readily on the surface of charcoal and why?

NH3 or O2.

20. (a) Give an example of industrial application of formation of coordination compound.

(b) Write the IUPAC name of [CoCl(ONO)(en)2] NO3.

(c) What is meant by the term ‘coordination number’?

21. (a) Explain why high temperatures are required in nuclear fusion reactions?

(b) Starting with 2.0 g of a radioactive sample, 0.50g of it was left after 5 days.

Calculate the mass that was left after just one day.

22. (a) How will you distinguish propanone and ethanol?

(b) Methylamine, CH3NH2, in water reacts with FeCl3 to form a precipitate of Fe(OH)3. Account.

(c) Give the IUPAC name of C6H5NHCOCH3.

23. (a) What are the functions of nucleic acids?

(b) Draw the zwitter ion form of the aminoacid, aniline.

(c) What are the differences between glucose and fructose?

24. (a) What is the advantage of detergent molecules associated with unbranched

hydrocarbon tail over its counterpart with branched hydrocarbon tail.

(b) What are monopropellants?

(c) What are broad spectrum antibiotics?

[5 - mark Questions]

25. (a) State the differences in the properties of white and red phosphorus.

(b) Arrange the following hydrides in the decreasing order of stability:

H2Se, H2O, H2Te, H2S,

(c) Complete and balance the following reaction:

Al2O3 + NaOH + H2O ®

(d) Describe the steps involved in the contact process for the manufacture of sulphuric acid.

OR

(a) Illustrate disproportionation with a suitable example.

(b) Why does Si not form a graphite like structure as carbon does?

(c) Complete and balance the following reactions:

XeF6 + KF ®

(d) Describe how bauxite is concentrated?

26. (a) Give reasons for the following:

(i) The d-block elements in general exhibit variable oxidation states.

(ii) The densities of post-lanthanoid elements are very high.

(b) Which is more stable: Mn2+ or Mn4+?

(c) (i) Name the chief ore of Copper.

(ii) Describe the principle of extraction of copper from the ore.

27. (a) How will you carry out the following conversions?

(i) Propanoic acid to ethanamine.

(ii) Toluene to benzene.

(b) An organic compound A has the molecular formula C5H10O. It does not reduce

Fehling’s solution, but forms an oxime with HCN. It also gives positive

iodoform test. Give two possible structures of A. Explain briefly how you arrive

at your conclusion.

 

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