North Maharashtra University 2009 B.Sc Chemistry Colligative properties. - Question Paper

weight of a solute.
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10. Derive the Van’t Hoff formula for Osmotic Pressure.
11. OR Using relation ranging from osmotic pressure and vapour pressure
deduced Van’t Hoff formula for osmotic pressure.
12. Write a note on abnormal molecular weight.
13. describe the term abnormal molecular weight. elaborate the reasons for
abnormal molecular weight.
14. discuss why molecular weight of non-electrolyte found from Colligative
property is identical as that of formula weight; but in case of electrolyte it is
not identical as that of formula weight.
15. Vapour pressure of ether at 20oC is 442 mm and that of solution of 6.0 gm
of benzoic acid in 50 gm ether is 410mm at identical temperature. compute
the molecular weight of benzoic acid in ether. Molecular weight of ether is
74.
16. obtain the molecular weight of the solute when 1.03 gm of it current in 75
gm phenol freezes at 312.25 K. Latent heat of fusion of phenol = 26.5gm-
1.Freezing point of phenol= 313 K.
17. obtain molecular weight of boric acid if 0.4% boric acid is isotonic with 2.3%
sucrose solution. (Molecular weight of sucrose=342).
18. compute the boiling point of 3% solution of glucose in water. Kb for 100
gm water=5.20C.
19. Latent heat of fusion of phenol is 26.5 cal gm-1 and melting point is 400C.A
solution of 0.170 gm of an organic substance in 12.5 gm phenol freezes at
39.250C .Calculate the molecular weight of the organic substance.
20. calculate the Cryoscopic constant of benzene which freezes at 5.50C.The
molar enthalpy of fusion of benzene is 2.347 Kcalmole-1. (Molecular weight
of benzene= 78).
21. What will be the osmotic pressure of 3.5% sucrose solution at 200C?
(Molecular weight of sucrose=342).
22. 13.6 gm of cane sugar (molecular weight 342) dissolved in 20 gm of water
caused a depression of freezing point of water by 3.7oC.
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23. A solution containing 5gm of urea per 100gm of water. Vapour pressure of
pure water is 27.756 mm. compute vapour pressure of this solution at
identical temperature.
24. A solution of 1.35gm of substance in 71.4gm of water boils at 100.162oC.
compute the molecular weight of substance. Latent heat of vaporisation is
543 cal/gm
25. At 270C osmotic pressure of solution is 2.525 atmosphere. compute
concentration of solution.

ques. of 6 marks.

1. State and discuss Raoult’s legal regulations. What is relative lowering of vapour
pressure.
2. discuss how relative lowering of vapour pressure is used in determining
the molecular weight of solute.
3. What is vapour pressure lowering and relative vapour pressure lowering?
Show that relative lowering of vapour pressure depends on mole fraction
of solute in solution.
4. Show that for provided solvent depression of freezing point is proportional to
molality of solution when non-volatile solute is added in solvent.
Or Derive thermodynamically ?Tf= Kf X m.
5. What is elevation in boiling point? Show it is a Colligative property.
Or What is elevation in boiling point? Show that for a provided solvent
elevation in boiling point depends on molality of solution.
6. Prove thermodynamically elevation in boiling point is a Colligative
property.
Or Derive thermodynamically ?Tb= Kb X m.
7. Derive the formula for the elevation in boiling point.Hence describe
ebullioscopic constant.
8. describe Osmosis and osmotic pressure. Derive the relation ranging from
osmotic pressure and vapour pressure.
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9. explain the phenomenon of Osmosis and Osmotic pressure. discuss
Berkely and Hartley’s method for determination of osmotic pressure. provide
its advantages.
10. State the principle of Berkeley and Hartley method. define Berkely and
Hartley’s method for determination of osmotic pressure. provide its
advantages.
11. discuss the various Colligative properties. explain in brief the
dependence of elevation of boiling point on the concentration.
12. What is abnormal molecular weight? describe and discuss Van’t-Hoff factor.

Earning:   Approval pending.