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## Homework Statement

A 32.0 mL sample of hydrogen is collected over water at 20°C and 750.0 torr pressure. What is the volume of the dry gas at STP? (vapor pressure of water at 20°C = 17.5 torr)

## Homework Equations

Ptot = Pdry + Pwet

P1V1/T1 = P2V2/T2

## The Attempt at a Solution

Pdry = Ptot - Pwet = 750 - 17.5 = 732.5 torr

V1 = P2V2T1/P1T2 = (732.5 torr)(32 mL)(298K)/(760 torr)(293 K) = 31.3 mL

The answer in the answer key gives 28.7 mL