Question

The following is a graph plotted between the vapour pressure of two volatile liquids against their respective mode fractions. Which of the following statement is/are correct?

• A. When $x_A=1$ and $x_B=0$, then $P=P_A^0$
• B. When $x_B=1$ and $x_A=0$, then $P=P_B^0$
• C. When $x_A=1$ and $x_B=0$, then $P<P_B^0$
• D. When $x_B=1$ and $x_A=0$, then $P>P_A^0$

Answer 1

Answer: (A), (B), (C), (D)

From the graph, we can observe that $p_A^0<p_B^0$
The vapour pressure at any $x$ can be given as
$P=\left(p_B^0-p_A^0\right)\times x_B+p_A^0$
Also, $x_A+x_B=1$ (Binary system)
So, at $x_A=1,x_B=0$ and $P=p_A^0<p_B^0$
and
at $x_B=1,x_A=0$ and $P=p_B^0>p_A^0$
Hence, options A, B, C and D are correct