Burning hydrogen produced 9 grams of water. Determine the mass and amount of oxygen reacted.

m (H2O) = 9 g.
Determine the mass and amount of oxygen reacted.
We write down the solution.
First, we write down the equation of reactions, then we equalize it.
O2 +2 H2 = 2 H2O
We calculate the molar mass of oxygen and water. We write down the solution.
M (O2) = 16 * 2 = 32 g / mol.
M (H2O) = 1 * 2 + 16 = 2 + 16 = 18 g / mol.
Next, we find the mass of oxygen that has reacted.
X g oxygen – 9 g water
32 g / mol oxygen – 2 * 18 g / mol water
X = 32 * 9: (2 * 18) = 8 g of oxygen.
Let’s determine the amount of oxygen.
n (O2) = 8/32 = 0.25 mol.
Answer: m (O2) = 8 g; n (O2) = 0.25 mol.