Question

Determine the enthalpy change (ΔH) for the combustion of ethanol as shown in the reaction C_2H_5OH(g) + 3O_2(g) → 2CO_2(g) + 3H_2O(g), given ΔH = 1278 kJ.

a) 1278 kJ
b) -1278 kJ
c) 639 kJ
d) -639 kJ

Answer 1

The enthalpy change for the combustion of ethanol is -1276 kJ/mol.

Step-by-step explanation:

The enthalpy change for the combustion of ethanol can be calculated using the enthalpies of formation of the reactants and products.

Given the enthalpies of formation are: C₂H5OH(I) -278 kJ/mol, H₂O(I) -286 kJ/mol, and CO₂(g) -394 kJ/mol.

The enthalpy change for the reaction is equal to the sum of the enthalpies of formation of the products minus the sum of the enthalpies of formation of the reactants.

Therefore, the enthalpy change for the combustion of ethanol is: ΔH = (2 × -394 kJ/mol) + (3 × -286 kJ/mol) - (-278 kJ/mol) = -1276 kJ/mol.

Hence, the enthalpy change (ΔH) for the combustion of ethanol is -1276 kJ/mol.