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# The correct option for the value of vapour pressure of a solution at 45°C with benzene to octane in molar ratio 3: 2 is:

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The correct option for the value of vapour pressure of a solution at 45°C with benzene to octane in molar ratio 3: 2 is:

[At 45°C vapour pressure of benzene is 280 mm Hg and that of octane is 420 mm Hg. Assume Ideal gas]

(1) 160 mm of Hg

(2) 168 mm of Hg

(3) 336 mm of Hg

(4) 350 mm of Hg

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Correct answer: (3) 336 mm of Hg

Explanation:

$$\frac{n_B}{n_o}$$ = $$\frac{3}{2}$$

nB = 3, no = 2

nTotal = 3 + 2 = 5

XB = $$\frac{n_B}{n_r}$$ = $$\frac{3}{5}$$

Xo = $$\frac{n_o}{n_r}$$ = $$\frac{2}{5}$$

Ps = P'BXB + P'oXo

Ps = 280 x $$\frac{3}{5}$$ + 420 x $$\frac{2}{5}$$

= 336 mm of Hg

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