a) (i) Define the term 'standard enthalpy of combustion'. (ii) State Hess's Law of constant heat summation.

b) Using the following standard enthalpies of formation, calculate the standard enthalpy of combustion of ethanol (C2H5OH):
ΔHf°[CO2(g)] = -394 kJ mol⁻¹
ΔHf°[H2O(l)] = -286 kJ mol⁻¹
ΔHf°[C2H5OH(l)] = -278 kJ mol⁻¹

c) (i) Explain why the combustion of ethanol is described as an exothermic reaction.
(ii) Sketch an energy profile (reaction coordinate) diagram for the combustion of ethanol, labelling the reactants, products, activation energy (Ea) and enthalpy change (ΔH).

Question

a) (i) Define the term 'standard enthalpy of combustion'. (ii) State Hess's Law of constant heat summation.

b) Using the following standard enthalpies of formation, calculate the standard enthalpy of combustion of ethanol (C2H5OH):
   ΔHf°[CO2(g)] = -394 kJ mol⁻¹
   ΔHf°[H2O(l)] = -286 kJ mol⁻¹
   ΔHf°[C2H5OH(l)] = -278 kJ mol⁻¹

c) (i) Explain why the combustion of ethanol is described as an exothermic reaction.
   (ii) Sketch an energy profile (reaction coordinate) diagram for the combustion of ethanol, labelling the reactants, products, activation energy (Ea) and enthalpy change (ΔH).

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