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

Let’s compose the equation for the reaction of water decomposition:
2H2O = 2H2 + O2;

The molecular weight of water is 18 g / mol. Let’s find the amount of substance near the water:
90/18 = 5 mol;

There is the same coefficient in front of hydrogen as t in front of water. This means that the amount of substance in hydrogen is 5 mol. Let’s find the volume of hydrogen:
22.4 * 5 = 112 liters;

There is a coefficient in front of oxygen that is 2 times less than in front of water. This means that the amount of substance in oxygen is 2.5 mol. Let’s find the volume of oxygen:
2.5 * 22.4 = 56 liters;

Answer: the volume of hydrogen is 112 liters, the volume of oxygen is 56 liters.