Question

calculate the amount, in moles, of oxygen required for the complete combustion of hydrogen to produce 2.50 moles of water​

Answer 1

According to reaction below, when one mol of oxygen reacts with two mol of hydrogen, two mol of water is produced. Thus, when 2.5 mol of oxygen reacted with hydrogen, 2 * 2.5 mol = 5 mol of water is produced. The molar mass of water is 18 g/mol. One mol of water weighs 18 g. 5 mol of water weights 5 * 18 = 90 g.

O2 + 2 H2 = 2 H2O

Answer: 90 g.