Concept:Enthalpy of neutralization is the heat change when one mole of water is formed from the reaction between an acid and a base.
Explanation:For a strong acid and a strong base, the actual chemical change is the same:
H+(aq)+OH−(aq)→H2O(l)Therefore, the enthalpy of neutralization remains almost constant, close to
−57.1 kJ/mol.
This heat change can be measured directly with a calorimeter.
Neutralization is exothermic, so its enthalpy change is negative, not positive.
When a weak acid or a weak base is used, some heat is consumed to complete ionisation, so the magnitude of the enthalpy of neutralization becomes smaller, not higher.
Hence, the correct statement is that it is constant for a strong acid and a strong base.
Answer:A. is constant for a strong acid and a strong base