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COMEDK · Chemistry · 17. Solutions

A non-volatile solute A weighing 60 g when dissolved in 212 g of the solvent Xylene reduces its vapour pressure to \(60 \%\). What is the Molar mass of A in \(\mathrm{g} / \mathrm{mol}\) ? [MM of xylene \(=106 \mathrm{~g} / \mathrm{mol}\) ]

  1. A \(56\)
  2. B \(60\)
  3. C \(126\)
  4. D \(45\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(45\)

Step-by-step Solution

Detailed explanation

According to Raoult's law for a non-volatile solute, the relative lowering of vapour pressure is equal to the mole fraction of the solute: \(\dfrac{P^o - P_s}{P^o} = \dfrac{n_A}{n_A + n_X}\) Given that the vapour pressure is reduced to \(60\%\), we have \(P_s = 0.6 P^o\).…