Solutions Question 249

Question: Out of the following liquid pair which solution follows the positive deviation from Raoult’s law-

Options:

A) Acetone + Chloroform

B) Water + Nitric acid

C) Water + Hydrochloric acid

D) Benzene + Methanol

Show Answer

Answer:

Correct Answer: D

Solution:

(1) $ CH_3COCH_3 $ and $ CHCl_3 $ are volatile. On mixing, there is an increase in intermolecular H-bonding due to the formation of chloretone.

Thus, force of attraction between $ (CHCl_3-CH_3COCH_3) $ molecules is larger than between $ (CHCl_3-CHCl_3) $ and $ (CHCOCH_3-CH_3COOH_3) $ molecules.

Thus, vaporization decreases, a case of negative deviation. (2) As in [c], negative deviation. (3) When $ HCl $ is mixed with $ H_2O $ , force of attraction between $ HCl $ and $ H_2O $ molecules is increased (due to dissolution), hence vaporization decreased, a case of negative deviation. (4) $ CH_3OH $ molecules are joined by intermolecular H-bonding which provides a liquid state.

On adding benzene. H-bonding breaks and the force of attraction between $ CH_3OH $ and benzene molecules is less than between $ CH_3OH-CH_3OH $ and between benzene-benzene. Hence, more is the vaporization of mixture. Thus a case of positive deviation.



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