Question

A 0.90 g sample of liquid water was introduced into an evacuated 2.00 L flask, which was then sealed and

heated to 37°C. What percentage, by mass, of the water remained as liquid? [Vapor pressure of water at 37°C=48.2 torr.]

A)0%

B)82%

C)90%

D)18%

E)10%

Answer #1

let x be the fraction remained as liquid

mass of liquid water = 0.90 g

mass of vapourized = 0.9 (1 - x)

moles of water vapourized = 0.9 (1 - x) / 18.02

= 0.0499 (1 - x )

P V = n R T

0.0634 x 2 = 0.05 (1-x) x 0.0821 x 310

x = 0.900

**percentage of water remained = 90 %**

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