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28/09/2021 9:32 pm
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The enthalpy of neutralisation of NH4OH with HCl is -51.46 kJ mol–1 and the enthalpy of neutralisation of NaOH with HCl is -55.90 kJ mol–1. The enthalpy of ionisation of NH4OH is
(a) -107.36 kJ mol–1
(b) -4.44 kJ mol–1
(c) +107.36 kJ mol–1
(d) +4.44 kJ mol–1
1 Answer
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29/09/2021 11:10 am
Correct answer: (d) +4.44 kJ mol–1
Explanation:
HCl → H+ + Cl- .....(i)
NH4OH ⇌ NH4+ + OH-
ΔH = x kJ mol–1 .....(ii)
H+ + OH- → H2O
ΔH = -55.90 kJ mol–1 ......(iii)
(from neutralisation of strong acid and strong base)
From equation (i), (ii) and (iii)
NH4OH + HCl → NH4+ + Cl- + H2O
ΔH = -51.46 kJ mol–1
∴ x + (-55.90) = -51.46
x = -51.46 + 55.90
= 4.44 kJ mol–1
∴ Enthalpy of ionisation of NH4OH is
= 4.44 kJ mol–1