# Comparing vapour pressure of 1 molar vs 1 molal solution of sodium chloride

Say, we have 1 molar solution of $$\ce{NaCl}$$ and 1 molal solution of $$\ce{NaCl}$$. Among these, which will have maximum vapour pressure?

I know that vapour pressure will depend on the number of $$\ce{Na+}$$ and $$\ce{Cl-}$$ ions, but how do we determine which has greater amount? Like one is 1 mol in 1 L while other is in 1 kg.

• You need to use the density of water at the same temperature to determine the conversion factor between molality and molarity. – Buck Thorn May 20 at 9:49