Question

A graph of vapour pressure and temperature for three different liquids $X,Y$ and $Z$ is shown below:
The following inferences are made:
A) $X$ has higher intermolecular interactions compared to $Y$
B) $X$ has lower intermolecular interactions compared to $Y$
C) $Z$ has lower intermolecular interactions compared to $Y$
The correct inference(s) is/are:

• A. $C$
• B. $A$
• C. $B$
• D. $A\text{and}C$

Answer 1

The correct option is C $B$

As shown in the plot below, for the same T, the vapour pressure of $X$ is the highest and of $Z$ is the lowest. Now, that means with the same average K.E. of $X,Y$ and $Z$ molecules, the $X$ molecules are able to compensate their respective intermolecular forces better. So, $X$ molecules have the highest vapour pressure. Which implies that the intermolecular forces in $X$ are the weakest among the three. The opposite could be said for $Z$ as well.