Calculate the volume of hydrogen and oxygen that are formed during the decomposition of 90 g of water.

2H2O = 2H2 + O2.

Obviously, 4 g of hydrogen and 32 g of oxygen are formed from 2 * 18 g of water. Let’s determine how much is formed during the decomposition of 90 g of water:

90 g – x g

2 * 18 g – 32 g.

Hence x = 80 g is the mass of oxygen. Let’s find the mass of hydrogen: m = 90 – 80 = 10 g.

Now let’s find the quantities of substances:

n = m / Mr = 10/2 = 5 mol is the amount of hydrogen substance.

n = 80/32 = 2.5 mol is the amount of oxygen substance.

Knowing that 1 mole of gas at normal conditions occupies a volume of 22.4 liters, we find the volumes of gases:

V (H2) = 5 * 22.4 = 112 HP

V (O2) = 2.5 * 22.4 = 56 liters.