FeSO4 (s) plus 4H2 (g) gives 3Fe(s) plus 4H2O(l)
from the equation above i mole of FeSO4 reacted with 4 mole of H2 gas to give 3 moles of iron and 4 moles of water.There is a relationship between volume and equilibrium shift. Decrease in volume favor the side with less moles of a gas. since hydrogen is a gas a decrease in volume favor the forward reaction hence more Fe is produced.
