Question

Heat liberated with 100mL of 1N \[NaOH\] is neutralised by 300mL of 1N \[HCl\] is:
A.11.56 kJ
B.5.73 kJ
C.22.92 kJ
D.17.19 kJ

Answer 1

Hint: When a strong base is added to a solution a strong acid neutralisation reaction takes place. Equal moles or equal volumes of the sodium hydroxide will react with hydrochloric acid to give sodium chloride and water accompanied with heat. Every one mole the reactants reacting to give salt and water liberate 57.3 kJ/mol of energy. If one of the compounds is exhausted then extra moles of the other will be left as it is in the solution and base the solution acidic or basic depending upon which of them is leftover in the solution.

Complete step by step answer:
The standard enthalpy change of neutralization for a strong acid and a strong base is given as -57.3 kJ/mol. So, for Every one mole the reactants react to give salt and water liberate 57.3 kJ/mol of energy and hence to find total energy liberated we can find the total number of moles of the acid and base reacting.
Number of equivalents or moles = Normality × Volume.
Hence, the heat liberated with 100 ml of 1 N \[NaOH\] is neutralised by 300 mL of 1 N \[HCl\] is \[\dfrac{57.3\times 100mL\times 1N}{1000mL/1}\] = 5.73 kJ
Hence the correct option is B which is 5.73 kJ.

Note:
Neutralization can be defined as a chemical reaction in which acid and a base react quantitatively with each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution if both acid and base are present in equivalent amounts. If we consider a neutralization reaction between a weak acid and base, then some of the energy liberated is used in dissociating the weak acid and base. So, the final amount of energy liberated is a little less.