Question

With a fact that at STP a mole of a gas occupies 22.4 L, calculate the entropy change

of mixing of 2.8 litres of O2 with 19.6 litres of H2 at STP. Assume the gases to behave

ideally

Answer 1

The Mixing of Ideal Gases:

is the mole fraction!

n (O2) = 2.8 / 22.4 = 0.125 mol

n (H2) = 19.6 / 22.4 = 0.875 mol

Total: 0.125 mol + 0.875 mol = 1 mol

mole fraction = 0.125 (O2)

mole fraction = 0.875 (H2)

Entropy change = - 1 * 8.314 * (0.125 ln(0.125) + 0.875 ln (0.875))

Entropy change = +3.13 J/K