1. Balanced Chemical Equation:

The balanced chemical equation for the formation of water from oxygen and hydrogen is:

2 H₂ + O₂ → 2 H₂O

2. Mole Ratios:

The equation tells us that:

* 1 mole of oxygen gas (O₂) reacts with 2 moles of hydrogen gas (H₂) to produce 2 moles of water (H₂O).

3. Calculation:

You want to make 4 moles of water. Since the ratio of oxygen to water is 1:2, you'll need half the number of moles of oxygen.

* Moles of oxygen needed = (4 moles of water) / 2 = 2 moles of oxygen

Therefore, you need 2 moles of oxygen gas to make 4 moles of water.