Question

The complete combustion of ethanol, to form CO2(g) and H2O(g) at constant pressure releases 726.7 kJ of heat per mole of (a) Write a balanced thermochemical equation for this reaction. a) Draw an enthalpy diagram for the reaction.

Answer 1

(a) First, we need to write the combustion reaction for ethanol (CH3CH2OH)

CH3CH2OH + O2 → CO2 + H2O

Then, we need to balance this equation. To do that, remember to start with C, then move on to H and finally balanced the amount of O:

CH3CH2OH + 3 O2 → 2 CO2 + 3 H2O

(b) Since this is a reaction that realeases heat (726.7 kJ /mol of ethanol), we know that is an exothermic reaction and the general scope of an enthalpy diagram would be like this:

Where, for the combustion of ethanol, the reactants would be CH3CH2OH + O2, the products would be CO2 + H2O, and ΔH would be -726.7 kJ/mol