Solutions and Colligative Properties - Result Question 58
####29. $1.22 g C _6 H _5 COOH$ is added into two solvents and data of $\Delta T _b$ and $K _b$ are given as :
(i) In $100 g CH _3 COCH _3 \Delta T _b=0.17, K _b=1.7 K kg / mol$
(ii) In $100 g$ benzene, $\Delta T _b=0.13$ and $K _b=2.6 K kg / mol$
Find out the molecular weight of $C _6 H _5 COOH$ in both the cases and interpret the result.
$(2004,2 M)$
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Solution:
- (i) $\Delta T _b=K _b \cdot m _2$
$$ \Rightarrow \quad 0.17=1.7 \times \frac{1.22}{M} \times \frac{1000}{100} \Rightarrow M=122 $$
(ii) $0.13=2.6 \times \frac{1.22}{M} \times \frac{1000}{100} \Rightarrow M=244$
The above molar masses suggests thapt benzoic acid is monomeric in acetone while dimeric in benzene.
