Calculate enthalpy change

Question

Use values of standard enthalpies of formation to calculate the enthalpy change for the reaction below: 

CO(g)+2H2(g)→ CH3OH(l)CO(g) + 2H2(g) → CH3OH(l)

Give the quantity (rounded to the nearest whole number) and unit (kJ) and don't forget the + or - sign. 

Answer 1

Products are formed: heats of formation apply

Reactants are unformed: subtract heats of formation

Heats of formation are given as kJ/mole of compound formed from elements in their natural states.

(1 mole methanol) *(Delta H formation of methanol) - (1mole CO)(Delta H formation of CO) = ΔH_rxn

You could also subtract 2ΔH_f⁰ of H₂(g), but that is = 0 as it is an element in its natural state.

Heats of formation are in table of thermodynamic data in textbook.

Take care.