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.
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