Question

When the metal sample reacts with acid, the gas evolved will be collected over water; the gas is said to be "wet". What is the composition of the wet gas? How can the partial pressure of hydrogen be obtained from the total pressure of wet gas? From where will you obtain the necessary data to determine the pressure of hydrogen gas?

Answer 1

Ptotal = pH2 + pH2O
Ptotal is what you read as the room pressure. pH2O is the vapor pressure of H2O which you can obtain from tables in your book at the corresponding temperature.

Answer 2

hgh