Question

Two liquids $X$ and $Y$ form an ideal solution. At $300K$, vapour pressure of the solution containing $1mol$ of $X$ and $3mol$ of $Y$ is $550mmHg$. At the same temperature, if $1mol$ of $Y$ is further added to this solution, vapour pressure of the solution increases by $10mmHg$. Vapour pressure (in $mmHg$) of $X$ and $Y$ in their pure states will be ______ respectively.

• A. $200$ and $300$
• B. $300$ and $400$
• C. $400$ and $600$
• D. $500$ and $600$

Answer 1

The correct option is C $400$ and $600$

$0.25P_X^0+0.75P_Y^0=550$ mm

$0.20P_X^0+0.80P_Y^0=560$ mm

$P_X^0+3P_Y^0=2200$ ..........(1)

$P_X^0+4P_Y^0=2800$ ...........(2)

From equation (1) and (2) we get

$P_Y^0=600$ mm

$P_X^0=400$ mm

Thus vapour pressure of X and Y in their pure state will be 400 and 600 mm of Hg respectively.

Hence, the correct option is $C$