Question

50 ml of .100M hdrochloric acid solution is completely neutralized with sodium hydroxide solution. in the process 279 joules of heat is liberated. What is the enthalpy of neutralization for the reaction between hydrochloric acid and sodium hydroxide?

Answer 1

Ans. Balanced reaction:       HCl(aq) + NaOH(aq) ----------> NaCl(aq) + H₂O

# Moles of HCl taken = Molarity x Volume of solution in liters

                                    = 0.100 M x (0.050 L)

                                    = 0.005 mol

# Given, neutralization of 0.005 mol HCl liberates 279 J energy.

Molar enthalpy of neutralization = Amount of heat liberated / Moles of HCl neutralized

                                    = -279 J / (0.005 mol)

                                    = -55800 J/ mol

                                    = - 55.8 kJ/mol

Note: The –ve sign indicates that heat is being liberated.