Question

At 25${}^o$C, the vapour pressure of methyl alcohol is 96.0 torr. What is the mole fraction of CH${}_3$OH in a solution in which the (partial) vapor pressure of CH${}_3$OH is 23.0 torr at 25${}^o$C?

• A. $0.24$
• B. $0.25$
• C. $0.26$
• D. $0.27$

Answer 1

The correct option is A $0.24$

According to Raoult's law, $p=p^0\times x$

p = partial vapour pressure of methanol

$p^0=$ pure vapour pressure of methanol

x = mole fraction of methanol.

Substitute values in the above expression

$23.0=96.0\times x$

Hence, the mole fraction of methanol is 0.24.

Option A is correct.