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 Na₂SO₄
(c) Addition of 1.00 molal KI
(d) Addition of water

Answer 1

Addition of water in an aqueous solution of 1.00 molal in KI will cause the vapour pressure of the solution to increase.

• As we know that, surface area and vapour pressure are proportional to each other, as the surface area increases, the vapour pressure also increases.
• However, the dilution (addition of solvent) increases the surface area of of liquid, in turn resulting in the increased vapour pressure.