1. Tardigrade
  2. Question
  3. Chemistry
  4. At 20° C, the vapour pressure of benzene is 70 torr and that of methyl benzene is 20 torr. The mole fraction of benzene in the vapour phase at 20° C above an equimolar mixture of benzene and methyl benzene is × 10-2. (Nearest integer)

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Q. At $20^{\circ} C$, the vapour pressure of benzene is $70$ torr and that of methyl benzene is $20$ torr. The mole fraction of benzene in the vapour phase at $20^{\circ} C$ above an equimolar mixture of benzene and methyl benzene is ________ $\times 10^{-2}$. (Nearest integer)

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Solution:

$P_{B}^{\circ}=40$
$P_{T}^{\circ}=20$
$K_{B}=0.5=K_{T}$
Now $y_{B}=\frac{K_{B} P_{B}^{\circ}}{K_{B} P^{\circ}{ }_{B}+K_{T} P^{\circ}}$
$=\frac{70 \times 0.5}{70 \times 0.5+20 \times 0.5}$