Question

How can I calculate the molar volume of Hydrogen gas?

Answer 1

Molar volume, or volume of one mole of gas , depends on pressure and temperature, and is 22.4 liters - at 0 °C (273.15 K) and 1 atm (101325 Pa), or STP (Standard Temperature and Pressure), for every gas which behaves similarly to an ideal gas. The ideal gas molar volume increases to 24.0 liters as the temperature increases to 20 °C (at 1 atm).

For an ideal gas, the attractive or repulsive interactions between the molecules of gas can be neglected, therefore we can treat this gas as "ideal". (Side Note: interaction forces between specific gases create conditions for non-ideal gas situations)

The actual molar volume of hydrogen can be exactly calculated from the experimental density of that gas, that is 0,0899 g/L at 0 °C (1 atm ) and 0.0837 g/L at 20 °C (1 atm), knowing that one mole of dihydrogen (`H_2`) amounts to 2,0159 g/mol.

Thus, if 0,08988 grams amount to 1 liter, a mole will be as big as 2,0159/0,0899 = 22,42 liters at STP (0 °C - 1 atm) and 2,0159/0,0837 = 24,1 liters.

These values of true molar volume of hydrogen are very close to the ideal gas values of 22,41 L/mol and 24,0 L/mol at 0 °C and 20 °C, respectively, thus confirming that hydrogen gas behaves almost ideally.