Question

Is the heat/mol rxn value for the reaction of CH3COOH + OH- any different than the value for CH3COOH(aq) + NaOH(aq)? Explain.

Answer 1

Standard enthalpy of neutralization (heat of reaction of acid-base reaction) is the amount of energy produced when an acid and base reacts to produce 1 mol of water molecules.

Order of heat of reaction: (strong acid- strong base) > (Strong acid-weak base) = (Weak acid-strong base) > (weak acid- weak base).

Reaction 1: CH₃COOH + OH^- ----------> dH_(rxn1)

Reaction 2: CH₃COOH + Na⁺OH^- ------> dH_(rxn2)

Case 1: dH_(rxn1) = dH_{(rxn2) ;} if OH^- comes from a strong base similar to NaOH.

Case 2: dH_(rxn1) < dH_{(rxn2) ;} if OH^- comes from a weak base like H₂O or alcohol, etc.

Carboxylic acids are weak acid. Heat of neutralization of carboxylic acid and strong base (here, NaOH) is larger than that of carboxylic acid and weak base (like H₂O and alcohol).