Question

Calculate the standard enthalpy change (∆H°) for the combustion of methane (CH4(g)) given the balanced equation: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)(Note: The values of standard enthalpies of formation of CO2(g), H2O(l) and CH4(g) are -393.5 kJ/mol, -285.8 kJ/mol, and -74.8 kJ/mol, respectively)

Answer 1

To calculate the standard enthalpy change  H  for the combustion of methane, we can use the following equation:H = Hf products  - Hf reactants where Hf represents the standard enthalpy of formation.For the given balanced equation:CH4 g  + 2O2 g   CO2 g  + 2H2O l The standard enthalpies of formation are:Hf CH4 g   = -74.8 kJ/molHf O2 g   = 0 kJ/mol  since O2 is in its standard state Hf CO2 g   = -393.5 kJ/molHf H2O l   = -285.8 kJ/molNow, we can plug these values into the equation:H = [1   -393.5 kJ/mol  + 2   -285.8 kJ/mol ] - [1   -74.8 kJ/mol  + 2  0 kJ/mol]H =  -393.5 - 571.6 + 74.8  kJ/molH = -890.3 kJ/molSo, the standard enthalpy change for the combustion of methane is -890.3 kJ/mol.