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