What is the partial pressure of the hydrogen gas collected?

May 7th at 1:58 am By: Chem Man

The vapor pressure water at 30 C is 31.8 torr. (Source: http://intro.chem.okstate.edu/1515SP01/Database/VPWater.html ).

P(total) = P(H2) + P(H2O)
P(H2) = P(total) – P(H2O) = 728 – 31.8 = 696 mmHg.
696 mmHg x (1 atm / 760 mmHg) = 0.916 atm

Use the ideal gas law to find the moles of H2 produced, then convert to mass in grams.
PV = nRT
n = PV / RT = (0.916 atm x 0.720 L) / (0.08206 L atm / K mol x 303 K) = 0.0265 mol H2

1 mol H2 has a mass of 2.016 g.
0.0265 mol H2 x (2.016 g / 1 mol) = 0.535 g H2