The balanced chemical equation for the complete combustion of propane C3H8 is:C3H8 + 5O2 3CO2 + 4H2OFrom the balanced equation, we can see that 1 mole of propane reacts with 5 moles of oxygen gas to produce 3 moles of carbon dioxide and 4 moles of water.Now, we are given that the reaction produces 5 moles of carbon dioxide and 4 moles of water. To find the moles of oxygen gas required, we can use the stoichiometric ratios from the balanced equation.First, let's find the moles of propane required to produce 5 moles of carbon dioxide: 5 moles CO2 1 mole C3H8 / 3 moles CO2 = 5/3 moles C3H8Now, let's find the moles of oxygen gas required to react with the calculated moles of propane: 5/3 moles C3H8 5 moles O2 / 1 mole C3H8 = 25/3 moles O2So, 25/3 moles of oxygen gas are required for the reaction to produce 5 moles of carbon dioxide and 4 moles of water.