Question

What is the enthalpy change when 1.50 moles of methane (CH4) is burned in excess oxygen gas (O2) under standard conditions, if the combustion reaction releases 890.4 kJ of heat? (Assuming all reactants and products are in their standard states)

Answer 1

To calculate the enthalpy change for the combustion of 1.50 moles of methane, we can use the given information about the heat released during the reaction. The balanced chemical equation for the combustion of methane is:CH g  + 2O g   CO g  + 2HO l The given heat released is 890.4 kJ for the combustion of methane. This value is usually given per mole of methane. Therefore, we can calculate the enthalpy change for 1.50 moles of methane as follows:Enthalpy change  H  =  Heat released per mole of methane    Number of moles of methane H =  -890.4 kJ/mol    1.50 mol Note that the heat released is negative because it is an exothermic reaction  heat is released to the surroundings .H = -1335.6 kJThe enthalpy change for the combustion of 1.50 moles of methane under standard conditions is -1335.6 kJ.