CBSE Question Paper 2009 for Class 12 - Chemistry

by saumil shrivastava

General Instruction for CBSE question Paper

(i) All questions are compulsory

(ii) Marks for each question are indicated against it.

(iii) Question numbers 1 to 8 are very short-answer question and carry 1 mark each.

(iv) Question numbers 9 to 18 are short-answer question and carry 2 mark each.

(v) Question number 19 to 27 are also short-answer questions and carry 3 marks each.

(vi) Question number 28 to 30 are long-answer questions and carry 5 marks each.

(vii) Use Log tables, if necessary. Use of calculators are not allowed.

1. Which point defected in crystals does not alter the density of the relevant solid ?

2. Define the term 'Tyndall effect'.

3. Why is the froth flotation method selected for the concentration of Sulphide ores ?

4. Why is Bi(v) a stronger oxidant than Sb(v) ?

5. Give the IUPAC name of the following compound :

6. Write the structure of 3-oxopentanal.

7. Why is an alkylamine more basic than ammonia ?

8. Give an example of elastomers.

9. A reaction is of second order with respect to a reactant. how will the rate of reaction be effected if the concentration of this reactant is

(i) doubled,
(ii) reduced to half?

10. Explain the role of

(i) Cryolite in the electrolytic reduction of alumina.
(ii) Carbon monoxide in the purification of nickel.

11. Draw the structure of the following molecules :

(i) XeF_4
(ii) BrF_3

12. Complete the following chemical reaction equations :

(i) $P_{4(s)} + NaOH_{aq} + H_2O_{(l)} \longrightarrow$

(ii) $I^-{}_{(aq)} + H_2O_{l} + O_{3(g)} \longrightarrow$

13. Differentiate between molality and molarity of a solution. What is the effect of change in temperature of a solution on its molality and molarity ?

14. Which ones in the following pairs of substances undergoes S_N2 substitution reaction faster and why ?

15. Complete the following reaction equations :

16. Explain what is meant by

(i) a peptide linkage
(ii) a glycosidic linkage

17. Name two water soluble vitamins, their sources and the diseases caused due to their deficiency in diet.

18. Draw the structure of the monomers of the following polymers :

(i) Teflon
(ii) Polythene

What is the repeating unit in the condensation polymer obtained by combing HO_2CCH_2CH_2CO_2H (succinic acid) and H_2NCH_2CH_2NH_2 (ethylene diamine).

19. Iron has a body centred cubic unit cell with a cell edge of 286.65 pm. The density of iron has is 7.87 g $cm^{-3}$ . Use this information to calculate Avogadro's number (At. mass of Fe = 56 g $mol^{-1}$ ).

20. 100 mg of a protein is dissolved in just enough water to make 10.0 ML of solution. If this solution has an osmotic pressure of 13.3 mm Hg at $25^{^{\circ}}C,$ What is the molar mass of the protein ?

(R = 0.0821 L atm $Mol^{-1} K^{-1}$ and 760 mm Hg)

21. A first order reaction has a rate constant of $0.0051\ min^-1.$ If we begin with 0.10 M concentration of the reactant, what concentration of reactant will remain in solution after 3 hours ?

22. How are the following colloids different from each other in respect of dispersion medium and dispersed phase ? Give one example of each type.

(i) An aerosol (ii) A hydrosol (iii) An emulsion

23. Account for the following :

(i) NH_3 is a stronger base than PH_3

(ii) Sulphur has a greater tendency for catenation than oxygen.

(iii) Bonds dissociation energy of F_2 is less than that of Cl_2

Explain the following situations :

(i) In the structure of HNO_3 molecule, the N - O bond (121 pm) is shorter than N - OH bond (140 pm).

(ii) SF_4 is easily hydrolysed whereas SF_6 is not easily hydrolysed.

(iii) XeF_2 has a straight linear structure and not a bent angular structure.

24. For the complex [Fe(en)_2Cl_2]Cl, (en = ethylene diamine), Identify

(i) The oxidation number of iron,

(ii) The hybrid orbitals and the shape of the complex,

(iii) The magnetic behaviours of the complex,

(iv) The number of geometrical isomers,

(v) Whether there is an optional isomer also, and

(vi) Name of the complex. (At. no. of Fe = 26)

25. Explain the mechanism of the following reactions :

(i) Addition of Grignard's reagent to the carbonyl group of a compound forming an adduct followed by hydrolysis.

(ii) Acid catalysed dehydration of an alcohol forming an alkene.

(iii) Acid catalysed hydration of an alkene forming an alcohol.

26. Giving an example for each describe the following reactions :

(i) Hofmann's bromamide reaction
(ii) Gatterman reaction
(iii) A coupling reaction

27. Explain the following types of substances with one suitable example, for each case :

(i) Cationic detergent .
(ii) Food preservatives.
(iii) Analgesics.

28. (a) Define molar conductivity of a substances and describe how for weak and strong electrolytes, molar conductivity changes with concentration of solute. How is such change explained ?

(b) A voltaic cell is set up at $25^{^{\circ}}$ with the following half cells :
$Ag^+ (0.001 M) | Ag\ and \ Cu^{2+} (0.10 M) | Cu$
What would be the voltage of this cell ? $(E^{^{\circ}}{}_{cell} = 0.46 V)$

(a) State the relationship amongst cell constant of a cell, resistance of the solution in the cell and conductivity of the solution. How is molar conductivity of a solute related to conductivity of its solution ?

(b) A voltaic cell is set up at $25^{^{\circ}}$ with the following half-cells :
$Al | Al^{3+} (0.001 M)\ and \ Ni | Ni^{2+} (0.50 M)$ Calculate the cell volatge $[E^{^{\circ}}{}_{_{Ni^{2+} | Ni}} = -0.25\ V, E^{^{\circ}}{}_{_{Al^{3+} | Al}} = -1.66\ V]$

29. (a) Complete the following chemical reaction equations :

(i) $MnO^-_{4(aq)} + C_2O^{2-}_{4}_{(aq)} + H^+_{(aq)} \longrightarrow$

(ii) $Cr_2O^{2-}_{7}_{(aq)} + Fe^{2+}_{(aq)} + H^{+}_{(aq)} \longrightarrow$

(b) Explain the following observation about the transition/inner transition elements :

(i) There is in general an increase in density of element from titanium (Z = 22) to copper (Z = 29).

(ii) There occurs much more frequent metal-metal bonding in compounds of heavy transition elements $(3^{rd} Series).$

(iii) The members in the actinoid series exhibit a larger number of oxidation states than the corresponding member in the lanthanoid series.

(a) Complete the following chemical equation for reactions :

(i) $MnO^-_{4(aq)} + S_2O^{2-+}_{3}_{(aq)} + H_2O_{(l)} \longrightarrow$

(ii) $Cr_2O^{-}_{7(aq)} + H_2S_{(g)} + H^{+}_{(aq)} \longrightarrow$

(b) Give an explanation for each of the following observations :

(i) The gradual decrease ion size (actinoid contraction) from element to element is greater among the actinoids than that among the lanthanoids (lanthanoid contraction).

(ii) the greater number of oxidation states are exhibited by the member in the middle of a transition series.

(iii) With the same d-orbital configuration $(d^4)\ Cr^{2+}$ ion is reducing agent but $Mn^{3+}$ ion is an oxidising agent.