Hydrogen gas was collected in a gas-collecting bottle with a volume of 30.0 mL by water displacement on a day where the temperature was 24ºC and the barometric pressure was 98.125 kPa. The vapour pressure of water at 24ºC is 2.99 kPa. What would be the volume of hydrogen gas at STP if it was dry

Answer 1

(P1V1/T1) = (P2V2/T2)
Ptota = pH2 + pH2O. You are given Ptotal and pH2O.
98.125 = pH2 + 2.99
Solve for pH2(dry) and use that in the equation above. You know all but V2.