Ammonium sulfate was dissolved in water and some of the enthalpy changes were determined during the dissolution process.
(a)
Given the following information, construct an energy cycle to determine the standard
enthalpy change of hydration of the sulfate ion.
Enthalpy change of solution of ammonium sulfate +6.20 kJmol-1
Lattice energy of ammonium sulfate
-916 kJ mol
Enthalpy change of hydration of ammonium ion -336 kJ mol-1
[Ans: -238 kJ mol-']
(b) Comment on the solubility of ammonium sulfate in water.
(c) Explain the significance of the hydration value of the sulfate ion.
Ed) When ammonium sulfate has dissolved, the anions and cations are each surrounded by
a number of molecules. Draw a simple diagram to show how a water molecule can be
attached to an ammonium cation. Label the diagram to show the type of interaction
involved.