When water decomposes, 8 g of hydrogen are formed. How much oxygen is released at the same time.

1.Let’s find the amount of hydrogen substance by the formula:

n = m: M.

M (H2) = 2 g / mol.

n = 8 g: 2 g / mol = 4 mol.

2. Let’s compose the reaction equation for the decomposition of water.

2H2O ⟶ 2 H2 + O2.

Let’s find in what quantitative ratios are hydrogen and oxygen.

According to the reaction equation, there is 1 mole of oxygen for 2 mol of hydrogen. Substances are in quantitative ratios of 2: 1, that is, the amount of hydrogen substance is 2 times greater than the amount of oxygen substance.

n (H2) = ½ n (O2) = 4: 2 = 2 mol.

Let’s find the mass of oxygen by the formula.

m = n × M,

M (O2) = 16 × 2 = 32 g / mol.

m = 2 mol × 32 g / mol = 64 g.

Answer: 64 g.