A sample of hydrogen gas (H2) is produced in a laboratory by displacement of water. A 645 mL sample of hydrogen is collected at 25 degrees Celsius and a total pressure of 758 torr. Collecting gas by water displacement causes the gas to become saturated with gaseous water vapor. Thus the sample is a mixture, and the water vapor contributes to the total pressure of "wet" hydrogen. The partial pressure of water vapor in such a mixture is given by the vapor pressure of water. A table of experimentally determined water vapor pressures of water shows that the vapor pressure of water at 25 degrees Celsius is 24 torr. Calculate the pressure of the "dry" hydrogen in the mixture.

Answer 1

A lot of reading and most is just a description of the experiment. Don't get distracted by all the verbiage.
Ptotal = pH2 + pH2O
You know Ptotal and pH2O. Substitute and solve for pH2(dry).

Answer 2

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