JEE Main 2015 · 10 Apr · Shift 1 · Chemistry Q36

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ChemistrySingle correct+4 / -1Question 36 of 90

A solution at 20°C is composed of 1.5 mol of benzene and 3.5 mol of toluene. If the vapour pressure of pure benzene and pure toluene at this temperature are 74.7 torr and 22.3 torr, respectively, then the total vapour pressure of the solution and the benzene mole fraction in equilibrium with it will be, respectively :

35.0 torr and 0.480

38.0 torr and 0.589

30.5 torr and 0.389

35.8 torr and 0.280

Answer and worked solution

Official answer: B

$x_B=0.3$ : $p=0.3(74.7)+0.7(22.3)=22.41+15.61=38.0$ torr. In the vapour, $y_B=\frac{22.41}{38.0}=0.589$ .

Topics:Raoult's law and vapour pressure

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JEE Main 2015 · 10 Apr · Shift 1, Chemistry question 36