Question

The vapour pressure (VP) of a dilute solution of non-volatile solute is P and the VP of a pure solvent is $P^o$. The lowering of the VP is:

• A. $+ve$
• B. $-ve$
• C. $P/P^o$
• D. $P^o/P$

Answer 1

The correct option is A $+ve$

According to Raoult's law,
$\frac{P^o-P_s}{P^o}$= Mole fraction of solute =${\chi }_2$
and lowering is always positive.

Hence, the correct option is $\text{A}$