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Standard XII

Chemistry

Liquids in Liquids

At 20 0 C, ...

Question

At $20^{0} C$ , the vapour pressure of diethyl either is 44mm. When 6.4 g. of a non-volatile solute is dissolved in 50g. of either, the vapour pressure falls to 410mm. The Molecular weight of the solute is:

150

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130

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160

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180

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Solution

The correct option is B 130
$Δ_{P} = 440 - 410 = 30 m m$
$∴ \frac{Δ_{P}}{P_{0}} = x_{s o l u t e}$

$\Rightarrow \frac{30}{440} = \frac{\frac{6.4}{M}}{\frac{6.4}{M} + \frac{50}{74}}$

$\Rightarrow \frac{19.2}{M} + \frac{150}{74} = \frac{44 \times 6.4}{M}$

$\Rightarrow \frac{150}{74} = \frac{6.4 (44 - 3)}{M}$

$\Rightarrow M = \frac{6.4 \times 41 \times 74}{150}$

$\approx 130$

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At 200C, the vapour pressure of diethyl either is 44mm. When 6.4 g. of a non-volatile solute is dissolved in 50g. of either, the vapour pressure falls to 410mm. The Molecular weight of the solute is:

The correct option is B 130ΔP=440−410=30mm ∴ΔPP0=xsolute ⇒30440=6.4M6.4M+5074 ⇒19.2M+15074=44×6.4M ⇒15074=6.4(44−3)M⇒M=6.4×41×74150 ≈130

At $20^{0} C$ , the vapour pressure of diethyl either is 44mm. When 6.4 g. of a non-volatile solute is dissolved in 50g. of either, the vapour pressure falls to 410mm. The Molecular weight of the solute is: