Question

Define enthalpy of neutralisation. Why is its value constant for strong acid-strong base
neutralisation? Why is its value different if a weak acid is used in place of the strong acid

Answer 1

The enthalpy of neutralisation is the change in enthalpy that occurs when an acid and base undergo a neutralisation reaction to form one mole of water in natural states. Its value is constant for strong acid-strong base neutralisation because this reaction is just the reaction between OH- and H+ to make the water. If a weak acid is used in place of the strong acid the change of enthalpy will be different because weak acid does not fully dissociate and it requires energy.