In this decomposition reaction, we are given with the mass of KCl and the amount of oxygen gas to be produced is asked. The stoichiometric ratio of KCl to O2 is 2:3. Given the mass of KCl, we convert this to moles by dividing the given mass by its molecular weight, 74.55 g/mol equal to 1.1858 mol. As to the stoichiometry of the reaction, multiply 1.1858 by 3 and divide by 2 to get the moles of O2, which is equal to 1.78 mol or 56.92 grams oxygen.
