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

Options

A. addition of water
B. addition of NaCl
C. addition of `Na_(2)SO_(4)`
D. addition of 1.00 molal Kl

Answer

1

Explanation

Whenever we dissolve a nonvolatile solute (such as Kl) in a volatile solvent (such as `H_(2)O)`, the vapor pressure of the resulting solution is always less than the vapor pressure of solvent because in a pure solvent the entire surface in occupied by the molecules of the solvent but in the solution, the surface has both solute and solvent molecules. There-by, the number of solvent molecules gets reduced. Consequently, the number of solvent molecules escaping from the surface is corresponding reduced. Thus, the vapor pressure is also reduced.
On addition of water, the vapor pressure of the solution will increase on account of increase in the number of molecules of volatile component `(H_(2)O)` on the surface.