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AIIMS2001ChemistrySolutions

Vapour pressure of benzene at 30^ C is 121.8 ~mm . When 15 ~g of a non-volatile solute is dissolved in 250 ~g of benzene, its vapour pressure is decreased to 120.2 ~mm . The molecular weight of the solute is

Options

  1. A35.67 ~g
  2. B356.7 ~g
  3. C432.8 ~g
  4. D502.7 ~g

Correct answer

B. 356.7 ~g

Step-by-step solution

Relative lowering of vapour pressure is given by : P^0-P P^0 = w / m w / m+W / M Where, P^0= Vapour pressure of pure solvent P= Vapour pressure of solution w mass of solute m= molecular mass of solute W = mass of solvent M= molecular mass of solvent. For dilute solution 121.8-120.2 121.8 = 15 / m 250 / 78 m=356.265

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