Question

# Calculate the standard enthalpy changes for the combustion of a mole of methane and the combustion...

Calculate the standard enthalpy changes for the combustion of a mole of methane and the combustion of a mole of methanol.

The equation for combustion of methane is written as

CH4(g) + O2(g) 2H2O (l) + CO2 (g)

The standard enthalpy of reaction is given by the equation

H = sum(enthalpy of formation of products) - sum( enthalpy of formation of reactants)

H = 2 x ΔfH owater + ΔfH oCO2 - ΔfH omethane - ΔfH ooxygen

H = 2(-285.83) - 393.5 + 74.8 + 0 = -890.36 kJ/mol

this is the standard enthalpy changes for the combustion of a mole of methane

For methanol:

2CH3OH(g) + 3O2(g) 2CO2(g) + 4H2O (l)

CH3OH(l) + 3/2O2(g) CO2(g) + 2H2O (l)

H = sum(enthalpy of formation of products) - sum( enthalpy of formation of reactants)

H = 2 x ΔfH owater + ΔfH oCO2 - ΔfH omethanol - 3/2ΔfH ooxygen

H = 2(-285.83) - 393.5 + 238.4 + 0 = -726.7 kJ/mol

this is the standard enthalpy changes for the combustion of a mole of methanol