Calculate the masses of hydrogen and oxygen formed during the decomposition of 72 g of water.

Decision:

1. Let’s write the equation for the reaction of water decomposition:

2H2O = 2H2 + O2;

2. Let’s count the amount of substance near the water:

72/18 = 4 mol;

3. The amount of substance in hydrogen is 4 mol, since the coefficients before water and hydrogen are the same. Let’s find the mass of hydrogen:

4 * 2 = 8 grams;

4. The amount of substance in oxygen is 2 mol, since the coefficient in front of oxygen is 2 times less than in front of water. Let’s find the mass of oxygen:

2 * 32 = 64 grams;

Answer: the mass of hydrogen is 8 grams, the mass of oxygen is 64 grams.