Two solutions A and B are prepared by dissolving 1 g of non-volatile solutes X and Y. respectively in 1 kg of water. The ratio of depression in freezing points for A and B is found to be 1: 4. The ratio of molar masses of X and Y is :

Question

Two solutions A and B are prepared by dissolving 1 g of non-volatile solutes X and Y. respectively in 1 kg of water. The ratio of depression in freezing points for A and B is found to be 1: 4. The ratio of molar masses of X and Y is : (A) 1: 4 (B) 1: 0.25 (C) 1: 0.20 (D) 1: 5

Tardigrade Admin · Accepted Answer

(Δ T fx /Δ T fy )=( k f ⋅ m x / k f ⋅ m y )=((1 / M x /1)/(1 / M y )1) ⇒ (1/4)=( M y / M x ) ⇒ M x: M y =1: 0.25

Q. Two solutions $A$ and $B$ are prepared by dissolving $1 g$ of non-volatile solutes $X$ and $Y$ . respectively in $1 k g$ of water. The ratio of depression in freezing points for $A$ and $B$ is found to be $1 : 4$ . The ratio of molar masses of $X$ and $Y$ is :

$1 : 4$

$1 : 0.25$

$1 : 0.20$

$1 : 5$

$\frac{Δ T _{f x}}{Δ T _{f y}} = \frac{k _{f} \cdot m _{x}}{k _{f} \cdot m _{y}} = \frac{\frac{1/ M _{x}}{1}}{\frac{1/ M _{y}}{1}}$
$\Rightarrow \frac{1}{4} = \frac{M _{y}}{M _{x}}$
$\Rightarrow M_{x} : M_{y} = 1 : 0.25$

Q. Two solutions A and B are prepared by dissolving 1g of non-volatile solutes X and Y. respectively in 1kg of water. The ratio of depression in freezing points for A and B is found to be 1:4. The ratio of molar masses of X and Y is :

1:4

1:0.25

1:0.20

1:5