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Question

Chemistry Question on Colligative Properties

Two solutions AA and BB are prepared by dissolving 1g1 g of non-volatile solutes XX and YY respectively in 1kg1 \,kg of water The ratio of depression in freezing points for AA and BB is found to be 1:41: 4 The ratio of molar masses of XX and YY is :

A

1:41: 4

B

1:0.251: 0.25

C

1:0.201: 0.20

D

1:51: 5

Answer

1:0.251: 0.25

Explanation

Solution

ΔTfxΔTfy​​=kfmxkfmy​​=1/Mx11/My1\frac{​Δ_Tf_x}{Δ_Tf_y}​​=\frac{​k_f​⋅mx}{k_f​⋅my}​​=\frac{\frac{1/M_x}{1}}{\frac{1/M_y}{1}}​​​

14=MyMx​​⇒\frac{1}{4}​=\frac{​M_y}{M_x}​​

Mx:My=1:0.25⇒M_x​:M_y​=1:0.25

Hence, the correct option (B):1:0.25\text{Hence, the correct option (B):} 1:0.25