hydrogen

chemister

If 277 L of LIQUID hydrogen has a mass of 19.7 kg, what volume will this amount of hydrogen occupy as a GAS at 25 degrees celcius and 1 atm?



Is there some kind of equation that I can use to make this problem easier?

THANKS!

Cesium

PV = nRT

You'll use this equation for almost every gas problem.

R (ideal-gas constant) = 0.0821 L-atm/mole-K
V = volume (L)
P = pressure (atm)
n = amount (moles)
T = temperature (K)

V = nRT/P

You need to convert the 19.7 kg H2 to moles H2 and the 25 C to Kelvin.

If you need more help, go ahead and ask.

chemister

Do you have to take into account the hydrogen beginning as a LIQUID and ending as a GAS?

Cesium

No because when you go from a liquid to a gas, the number of moles of H2 will still stay the same and therefore you can predict the volume.

chemister

When converting 19.7 Kg to moles would you use H2 (being 2.0158g) or just H (being 1.0079g)?

Cesium

Good question. Always use the diatomic molecule...so H2.

chemister

Thanks for your help. So if i have done things right my answer should be close to 2.39 X 10^5 L

Cesium

Yes I got a similiar answer. By the way, what value are you using for R? 0.0821 or something more precise?

chemister

For this problem I just used 0.0821, but usually I use 0.082057