If the pressure in the room is 759.2 torr and the vapor pressure of water is 23.8 torr, what is the pressure of hydrogen gas in the collection tube?

The partial pressure of Hydrogen gas can directly be calculated by simply taking the difference of the overall pressure and the vapour pressure of water. That is:

P (H2 gas) = 759.2 torr – 23.8 torr

P (H2 gas) = 735.4 torr

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.