JEE MAIN - Chemistry (2022 - 29th June Evening Shift - No. 16)
Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4 K. The ratio of molal elevation constant to molal depression constant (Kb/Kf) is _________.
Answer
3
Explanation
$$\begin{aligned}
&\Delta \mathrm{T}_{\mathrm{b}}=\mathrm{iK}_{\mathrm{b}} \mathrm{m} \\\\
&\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{iK}_{\mathrm{f}} \mathrm{m} \\\\
&\frac{4}{4}=\frac{\mathrm{K}_{\mathrm{b}} 1.5}{\mathrm{~K}_{\mathrm{f}} 4.5} \\\\
&\frac{\mathrm{K}_{\mathrm{b}}}{\mathrm{K}_{\mathrm{f}}}=3
\end{aligned}$$
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