Question

Explain why reactions involving a strong acid and a strong base all have values for standard enthalpy change of about -57 kJ mol^-1

Explain why neutralization reactions involving weak acids or weak bases have values which differ from those involving strong acids.

Answer 1

NaOH + HCl -------> NaCl + H2O   H = -57Kj/mole

NH4OH + HCl -------> NH4Cl + H2O H = -51.46 Kj/mole

NH4OH is weak base .So it is partially ionisable. Some amount of energy is required to completely ionisation of NH4OH

H of ionisation of NH4OH = [H of neutralisation of (HCl + NH4OH)-[H of neutralisation of HCl + NaOH)

                                            = -51.46-(-57) = 5.54KJ/mole

5.54 kj/mole energy is required ot ionisation of NH4OH