Question

Taking into account the vapor pressure of water, how many moles of hydrogen gas, n, are present in 345 ml at 752 torr and 29 ∘c? the value of the gas constant r is 0.08206 l⋅atm/(mol⋅k). you may also find the conversion

Answer 1

To make things simple, assume ideal gas. Then, we use the ideal gas equation.

PV = nRT

Since we are finding for n, the equation should be rearranged to

n = PV/RT

Make sure you are consistent with your units. If you use R = 0.08206 l⋅atm/(mol⋅k), the pressure should be:
P = 752 torr (1 atm/760 torr) = 0.98947 atm
The volume should be:
V = 345 mL (1 L/1000 mL) = 0.345 L
The temperature should be:
T = 29 + 273 = 302 K

Thus,

n = (0.98947 atm)(0.345 L)/(0.08206 l⋅atm/(mol⋅k))(302 K)
n = 0.01377 moles of hydrogen gas