JEE PYQ: Solutions And Colligative Properties Question 45
Question 45 - 2019 (12 Jan Shift 1)
Molecules of benzoic acid ($\text{C}_6\text{H}_5\text{COOH}$) dimerise in benzene. ‘w’ g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2 K. If the percentage association is 80, then w is:
[$K_f = 5$ K kg mol$^{-1}$, Molar mass of benzoic acid $= 122$ g mol$^{-1}$]
(1). (2.4 g)
(2). (1.0 g)
(3). (1.5 g)
(4). (1.8 g)
Show Answer
Answer: (1)
Solution
$i = 1 - \alpha/2 = 0.6$. $2 = 0.6 \times 5 \times \frac{w}{122} \times \frac{1000}{30}$. $w = 2.4$ g.
BETA
