How many moles of water are needed to produce 11.5 L of oxygen gas according to the following reaction at 0 °C and 1 atm?

Question

water (l) hydrogen (g) + oxygen(g)

??  moles water

Answer 1

The unbalance chemical reaction equation is then:

H₂O(l) → H₂(g) + O₂(g)

To balance it, we need to have 2 "O"s on the left side which drives 2 "H₂"s on the right side making the balanced chemical reaction equation:

2H₂O(l) → 2H₂(g) + O₂(g)

An important fact that you should have learned is that 1 mole of any gas at standard temperature and pressure (0 °C and 1 atm) occupies 22.4 liters. So 11.5 L would be (11.5/22.4) moles or 0.51339 moles of O₂.

Looking at the balanced chemical reaction equation, we see that 2 moles of water create 1 mole of oxygen gas so that means the number of moles of water would be 2(0.51339) = 1.03 moles of water