If you burn 53.8 g of hydrogen and produce 481 g of water, how much oxygen reacted?

The reaction:

2 H 2 + O 2 → 2 H 2 O

2 Hydrogen molecules react with 1 Oxygen molecule to create 2 molecules of water.

We have to convert 53.8 g of Hydrogen into moles:

53.8 : 2.02 g / moles = 26.63 moles

2 moles H 2 ↔ 1 mole O 2

26.63 moles H 2 ↔ 13.32 moles O 2

Mass (O 2) = 13.32 moles · 32 g/moles = 426.2 g

Answer: 426.2 grams of Oxygen.