Aug 212013

Time: 3 hours

Full Marks: 75
Pass Marks: 27

Group ‘A’

Attempt any fifteen questions. (2 × 15 = 30)

1. Calculate the percentage of sulphur in Na2S2O3 (Na = 23, S = 32 and O = 16). [Ans: 40.5%]
2. Calculate the number of moles of carbondioxide molecules in 2.24ml of carbondioxide at STP. [Ans: 0.0001 mole]
3. The element Ag consists of two isotopes: Ag-107 with natural abundance of 51.83% and Ag-109 with natural abundance of 48.17%, calculate the relative atomic mass of Ag. [Ans: Relative atomic mass of Ag = 107.96 amu]
4. Define intramolecular hydrogen bonding. Give one example.
5. Why is CO2 a non polar molecule?
6. Assign all the values of quantum numbers of electron of the configuration of 2p1.
7. Arrange the elements Na, Li and K in the increasing order of first ionization energy. Give reasons.
8. Write the Lewis structure of sodium sulphate.
9. Calculate the molarity of 2.12% aq. sodium carbonate. [Molecular mass of sodium carbonate = 106] (Transferred to grade 12)
10. State Hess’s law of constant heat summation. (Transferred to grade 12)
11. How does temperature change affect the equilibrium of the given reaction?

N2 + 3H2↔ 2NH3 (g) ΔH = -22.4 Kcal

12. Why is solid sodium chloride a non conductor of electricity?
13. Differentiate between ortho and para hydrogen.
14. Write down the resonating structures of ozone.
15. Why are noble gases chemically inactive?
16. Distinguish between alloys and amalgams. Give one example of each.
17. What happens when a piece of sodium is exposed to air?
18. Name two important ores of copper with their formulae.
19. Write the structures of (i) Aldehyde and (ii) Ester.
20. Account for the fact that chloroacetic acid is a stronger acid than acetic acid.
21. Write the possible isomers of C2H6O and give their IUPAC names.
22. Write chemical reactions involved when acetylene is passed through ammonical cuprous chloride.

Group ‘B’

Attempt any five questions. (5 × 5 = 25)

23. You are given,

Na2CO3 (aq) + 2HCl (aq) → 2NaCl (aq) + CO2 (g) + H2O (l)

If this reaction is carried out by mixing 2.12 g of Na2CO3 and 1.5 g of HCl,
i) find which is the limiting reactant. [Ans: Na2CO3 is limiting reactant.]
ii) calculate the amount of NaCl formed. [Ans: 2.34 g = 0.04 mole]
iii) calculate the volume of CO2 produced at STP. [Ans: 448 cc]
24. Specify oxidant and reductant in the following redox oxidation and balance it by ion electron method.

Zn + H+ + NO3 → Zn+2 + NH4+ + H2O

25. State Avogadro’s law. Apply the law to deduce the relationship between molecular mass and vapour density.
26. Compare the bleaching actions of sulphur dioxide and chlorine.
27. What happens when:
a) Ammonia solution is added to the copper sulphate solution drop by drop till excess.
b) The gas obtained by the action of marble upon dilute hydrochloric acid is passed through lime water till excess.
28. Write down the principle involved in the extraction of sodium by Down’s process with well labelled diagram.
29. Write the structure of an alkene which yields the mixture of acetaldehyde and formaldehyde upon ozonolysis. Suggest your answer with chemical reactions.

Group ‘C’

Attempt any two questions. (10 × 2 = 20)

30. Describe the manufacture of nitric acid by catalytic oxidation of ammonia.
31. a) Derive PV = nRT. b) When 2 gm of gaseous substance A, is introduced into an initially evacuated flask at 25oC, the pressure is found to be 1 atm and 3 gm of another gaseous substance B, is introduced in the same flask. The final pressure of the mixture of gases was found to be 1.5 atm. Assuming ideal behaviour, calculate the ratio of molecular mass of A and B. [Ans: MA:MB::1:3]
32. How is blister copper extracted from its sulphide ore? How is it refined electrolytically?
33. Write short notes on: (any two)
a) Extraction of calcium
b) Solubility curve and its application
c) Detection of nitrogen in organic compound
d) Polymerization