# Vapor pressure lowering

I have got this problem in my text book,

Consider these three mercury manometers. One of them has 1 mL of water placed on top of the mercury, another has 1 mL of a 1 m urea solution placed on top of the mercury, and the third one has 1 mL of a 1 m NaCl solution placed on top of the mercury. Identify X, Y, and Z with these solutions.

I got the answer in answer sheet is X = ${H_2}O$ , Y = $NaCl$ and Z = ${(NH_2)}_2{CO}$ . Can any one please explain me? Thanks in advance.

• – MaxW Jan 29 '17 at 3:16
• @MaxW but i'm confused whether Y = NaCl or not, i think Z = NaCl is more preferable – IAmBlake Jan 29 '17 at 3:32
• NaCl splits into two ions thus has more colligative influence than urea which the molecule dissolves as one thing. Scale in drawing obviously greatly exaggerated. – MaxW Jan 29 '17 at 3:45
• @MaxW sorry i couldn't get it. Can you please write your answer with proper description ? – IAmBlake Jan 29 '17 at 3:51