1. Tardigrade
  2. Question
  3. Chemistry
  4. At 25°C the vapour pressure of benzene, C6H6 (78 g/mole), is 93.2 Torr and that of toluene, C7H8 (92 g/mol), is 28.2 torr. A solution of 1.0 mole of C6H6 and 1.0 mol of C7H8 is prepared. Calculate the mole fraction of C6H6 in the vapour above this solution (assume the solution is ideal)

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Q. At $25^{\circ}C$ the vapour pressure of benzene, $C_{6}H_{6}$ (78 g/mole), is $93.2$ Torr and that of toluene, $C_{7}H_{8}$ (92\,g/mol), is 28.2 torr. A solution of 1.0 mole of $C_{6}H_{6}$ and 1.0 mol of $C_{7}H_{8}$ is prepared. Calculate the mole fraction of $C_{6}H_{6}$ in the vapour above this solution (assume the solution is ideal)

Solutions

Solution:

$Y_{B}=\frac{P_{B}^{o}\times X_{B}}{P} $
$Y_{B}=\frac{93.2\times0.5}{P}$
$Y_{T}=\frac{28.2\times0.5}{P}$
$\therefore \frac{Y_{B}}{Y_{T}}=3.3$ & $Y_{B}+Y_{T}=1$
On solving $Y_{B}=0.768$