Question

Assertion :Enthalpy of neutralization of ${CH}_{3}COOH$ by NaOH is less than that of HCl by NaOH. Because Reason: Enthalpy of neutralization of ${CH}_{3}COOH$ is less because of the absorption of heat in the ionization process.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

The reaction in which an acid and a base react to give a salt and water is called a neutralization reaction. Neutralization reactions are exothermic in nature. The heat change when one gram equivalent of an acid is completely neutralised by a base or vice versa in dilute solution is called the heat of neutralization.

The average enthalpy of neutralization of any strong acid by a strong base is found to be –57.7. This is because strong acids and strong bases are completely ionized in aqueous solutions. The aqueous solution of one gram equivalent of all strong acids contains the same number of $H^{+}$ ions. Similarly, the aqueous solution of one gram equivalent of all strong bases also contains the same number of $O{H}^{–}$. The neutralization reactions between strong acids and strong bases in aqueous solutions involve simply the combination of $H^{+}$ ions (from an acid) and $O{H}^{–}$ ions (from a base) to form unionized water molecules.

When strong acid and a weak base or weak acid and a strong

base or weak acid and weak base are mixed in equivalent amounts, the heat evolved or change in enthalpy is less than -57.7.

Hence, the correct option is $\text{A}$