CBSE Guess paper class XII Chemistry 2008 3



CBSE GUESS PAPER


CLASS: XII CHEMISTRY

Time allowed: 3Hours M.Marks: 70

General instructions

i) All questions are compulsory.

ii) Marks for each question is indicated against it

iii) Question numbers 1 to 5 are very short answer type questions, carrying 1 mark

each. Answer them in one word or in one sentence each

iv) Question numbers 6 to 12 are short answer type question, carrying 2 marks

each. Answer them in about 30 words each.

v) Question numbers 13 to 24 are short answer type questions, carrying 3

marks each. Answer them in about 40 words each.

vi) Question numbers 25 to 27 are long answer type questions, carrying 5

marks each. Answer them in about 70 words each.

vii) Use log tables if necessary. Calculators are not permitted.

1. What type of defect reduces the density of unit cell? 1

2. What is the effect of temperature on osmatic pressure of the solution? 1

3. Determine the order of the reaction if its half life is inversely proportional to the

initial concentration of the reactant. 1

4. Mention two uses of formaldehyde. 1

5. Write the IUPAC name of the compound

CH3 OCOCH2 CH2 COO CH3 1

6. What do you understand by radial probability function 4pr2R2? Draw the

radial probability function curve for 2s and 2p orbital. 2

7. Comment on the validity of the following statements: 2

(i) A reaction with DG0< 0 has always equilibrium constant greater than 1.

(ii) An exothermic reaction is always spontaneous.

8. The outer electronic configuration of two elements of lanthanoids are given below

(i) 4f1 5d1 6s2 (ii) 4f7 5d0 6s2. Determine the atomic number of these elements.

Determine the stable oxidation state of these elements. 2

9. Give two differences between conformational isomerism and configurational

isomerism. 2

OR

A compound having two chiral centers does not always have four stereo isomers.

Justify this statement with a suitable example. 2

10. Mention the differences between thermo setting and thermo plastic polymers.

11. Distinguish chemically between (i) Phenol and methanol (ii) Propan-1-ol and

propan-2-ol. 2

12. Complete the following chemical equations: 2

(i) U+ClF3®

(ii) Ca3(PO4)2 +SiO2 +C®

13. Write the ground state electronic configuration of N2. 3

(i) Determine the bond order of N2.

(ii) N2 and CO has same bond order, but CO is more reactive than N2. Why?

14. An element A crystallizes in FCC structure. 200g of this element has 24x1023

atoms. Density of unit cell is 7.2g/cm3. Calculate the radius of A. 3

Avagadro number= 6x 1023 mole- 1

15. The activation energy of a first order reaction at 270C is 54 KJ/mole. Activation

energy of the same reaction at the same temperature in the presence of a catalyst is 44 KJ/mole. How many times the reaction rate changes in the presence of catalyst at this temperature?

(R=8.314J/K/mole) 3

16. 0.85% solution of NaNO3 is 90% dissociated at 300K.Determine the 3

osmatic pressure of the solution.( R= 0.0821 L atm/K/mole. Molar mass of NaNO3=85u) OR 3

Determine the boiling point of 1M solution of KCl. Assume that KCl is 90% dissociated. Density of KCl solution is 1.05g/cm3. Molar mass of KCl=74.5u.

Kb= 0.52 K Kg mole- 1

17 (a) Predict the sign of entropy change for the reaction 3

CaCO3(s)®CaO(s) +CO2(g)

(b) You are provided with the following DrG0 values

S2 +2 O2 ® 2SO2 DrG0 = - 544 KJ/mole

2Zn +O2® 2ZnO DrG0 = - 480 KJ/mole

2Zn+ S2 ® 2ZnS DrG0 = - 293 KJ/mole

Show that roasting of ZnS to ZnO is a spontaneous process.

18. Explain the terms activity and selectivity of catalyst with examples. 3

19 (a) How is potassium dichromate prepared from chromite ore? 3

(b) Write the ionic equation of the reaction involved when KMnO4 is treated with

ferrous sulphate solution in acid medium.

20. Using Valence bond theory compare the structure and magnetic behavior of

(i) Ni (CO)4 (ii) [Ni (CN)4]2- Atomic number of Ni=28 3

21 (i) A radio active element of group 18 undergoes a decay. Determine the position of

the new nuclide.

(ii) Calculate the mass of 140 La in a sample whose activity is 3.7x1010Bq. Given

half life of 140 La = 40 hours. 3

22. Carry out the following conversions: 3

(i) Benzoyl chloride to benzaldehyde.

(ii) Hex-1-ene to pentanal

(iii) Hexane nitrile to 1-amino pentane.

23. Account for the following: 3

(i) In ammonalysis of halo alkanes primary amine is the only product when NH3

is taken in large excess.

(ii) Tert amine has lower boiling point than primary amine of comparable molar

mass,

(iii) Amide formed in acylation reaction of amine, does not react further with

acid halide.

24. Describe the following with suitable examples: 3

(i) Double base propellant (ii) Mordant dyes (iii) Broad spectrum antibiotics.

25. (i) Explain corrosion of iron as an electro chemical process. 5

(ii) The electrolysis of a metal salt solution was carried out by passing 4 amperes

for 45 minutes. It resulted in the deposition of 2.977g of the metal. If atomic

mass of the metal is 106.4g/mole, determine the charge carried by the metal

ion.

OR

(i) How does conductivity and molar conductivity of an electrolyte solution vary

with the dilution of the solution. 5

(ii) The E0 potentials of two reduction electrodes are Cu+/ Cu = + 0.52V and

Cu2+ / Cu+ = + 0.16 V. Calculate the work obtainable from the cell.

26 (a) Account for the following: 5

(i) PCl5 solid is ionic in nature.

(ii) SF6 is resistant to hydrolysis.

(iii) Inter halogen compounds are more reactive than halogens from which it is

made.

(b) Draw the structures of the molecules (i) P4O10 (ii) per oxo mono sulphuric acid.

OR

(a) Account for the following: 5

(i) PCl5 fumes in air.

(ii) Ga is smaller in size than Al.

(iii) PbO2 is a good oxidizing agent.

(b) Draw the structures of the molecules (i) SF4 (ii) IF4¯

27 (a) what are lipids? Based on their chemical composition, present a classification of

lipids. 5

(b) In reference to DNA molecule what do you under stand by the terms replication

and transcription.

OR 5

(a) Define the terms (i) codon (ii) native state of protein (iii) Denaturation of protein.

(b) Write the name of the nucleoside which is present only in (i) DNA (ii) RNA.

 

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