Question

The solubility of a salt at ${40}^{o}C$ is $25gm$ and at ${100}^{o}C$ it is $75$gm. A saturated solution of $1.5$gm of the salt is cooled from ${100}^{o}C$ to ${40}^{o}C$. How much salt will settle down?

• A. $5$gm
• B. $0.3$gm
• C. $1$gm
• D. $1.2$gm

Answer 1

Answer: (C)

$1$gm

Solubility of salt at ${100}^{o}C=75g$
Solubility of salt at ${40}^{o}C=25g$
$\therefore$ Ratio of solubility of salt at ${100}^{o}C$ and ${40}^{o}C=75:25$
$=3:1$
The saturated solution at ${100}^{o}C$ contains salt $=1.5g$
$\therefore$ At ${40}^{o}C$ the solubility will be-
$3:1=1.5:x$
$\therefore$ $x=0.5g$
Thus, the amount of salt that will settle down
$=1.5-0.5=1g$