Calculate the standard enthalpy change in kJ for the production of 15.2 g of CO2 (g) from a reaction where the

Question

Calculate the standard enthalpy change in kJ for the production of 15.2 g of CO2 (g) from a reaction where the reactants and products are:

reactants: CH4 (g) O2 (g)

products: CO2 (g) H2O (g)

Answer 1

The reaction is this: CH4 + 2 O2 --> CO2 + 2 H2O
This is a combustion reaction. ΔHr = -890 kJ / mol

ΔHr (the standard enthalpy change) = ΔHf(CH4) + 2*ΔHf(O2) - ΔHf(CO2) - 2*ΔHf(H2O)

ΔHf is the standard enthalpy change of formation for each compound. Any elemental compounds are zero (like O2)
So, ΔHr = 74.8 kJ/mol - 393.3 kJ/mol - 2* 286.2 kJ/mol = - 890.9 kJ/mol. These were found online, but you could also find them in a reference book, like the CRC handbook of chemistry and physics.

Determine the number of moles of CO2:
CO2 has a molecular weight of 44 g/mol. 15.2 g / 44 g/mol = 0.345 mol.

ΔH = -890.9 kJ/mol * 0.345 mol = -307.8 kJ