Question

An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase?

• A. Addition of NaCl
• B. Addition of Na${}_2$SO${}_4$
• C. Addition of 1.00 molal KI
• D. Addition of water

Answer 1

The correct option is D Addition of water

An aqueous solution is $1.00$ molal in $KI$. So, the addition of water will cause the vapour pressure to increase. This is according to Raoult's Law.

In the other three options, electrolyte undergo ionization, which leads to lowering of vapour pressure.

Hence, the correct option is $D$