Question

Calculate the standard enthalpy change for the combustion of methane gas (CH4) given the balanced chemical equation:CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)The relevant standard enthalpies of formation are:ΔHf°[CH4(g)] = -74.87 kJ/molΔHf°[CO2(g)] = -393.5 kJ/molΔHf°[H2O(l)] = -285.8 kJ/mol

Answer 1

To calculate the standard enthalpy change for the combustion of methane gas  CH4 , we can use the following formula:H =  Hf products  -  Hf reactants For the given balanced chemical equation:CH4 g  + 2O2 g  -> CO2 g  + 2H2O l The standard enthalpies of formation for the reactants are:Hf[CH4 g ] = -74.87 kJ/molHf[O2 g ] = 0 kJ/mol  since O2 is in its standard state The standard enthalpies of formation for the products are:Hf[CO2 g ] = -393.5 kJ/molHf[H2O l ] = -285.8 kJ/molNow, we can plug these values into the formula:H = [ -393.5 kJ/mol  + 2 -285.8 kJ/mol ] - [ -74.87 kJ/mol  + 0]H =  -393.5 - 571.6 + 74.87  kJ/molH = -890.23 kJ/molTherefore, the standard enthalpy change for the combustion of methane gas  CH4  is -890.23 kJ/mol.