2. Pentane reacts with an excess of oxygen to produce carbon dioxide and water. What is the enthalpy change of the reaction per mole of each of the following? a) oxygen b) carbon dioxide c) water 3. Determine the thermal energy released by the combustion of each of the following samples of hydrocarbons in an open system: a) 56.78 g pentane, C5H12() b) 1.36kg octane, C8H18() c) 2.344104g heptane, C7H16() 1. Hydrogen gas and oxygen gas react to form 0.534g of gaseous water. What is the enthalpy change? rH=241.8kJ/mol