Lattice enthalpies can be determined experimentally using a Born–Haber cycle and theoretically using calculations based on electrostatic principles.
The experimental lattice enthalpies of magnesium chloride, MgCl2 , calcium chloride, CaCl2 , strontium chloride, SrCl2 , and barium chloride, BaCl2 are given in section 18 of the data booklet. Explain the trend in the values.
Strontium is used as a red colouring agent in fireworks as it provides a very intense red colour. Use section 8 and 18 to calculate the enthalpy of atomisation for chlorine in strontium chloride.
A Group 1 bromide has an enthalpy of solution, ΔHӨsol , of 19.87 kJ mol-1 and the lattice enthalpy, ΔHӨlatt, is 691 kJ mol-1 . Use section 20 of the data booklet to identify the Group 1 ion, showing your working.
The same Group 1 metal from part c) forms an ionic lattice with another halide ion. This new ionic compound has a larger value for lattice enthalpy, ΔHθlatt. Suggest a formula for the new ionic lattice and justify your answer.
If sulfur is used as opposed to selenium in the lattice, what would you expect to happen to the value of the enthalpy of lattice dissociation. Explain your answer.
A student carried out a calorimetry experiment using 12.41 g of ammonium chloride and 12.50 cm3 of water. The temperature decreased from 23.7 °C to 17.3 °C. Construct a dissolution cycle for this reaction.
The enthalpy change for the hydration, ΔHθhyd , of the ammonium ion is -331 kJ mol-1. Use sections 19 and 20 and your answer to part a) to calculate the lattice enthalpy, ΔHθlatt, of ammonium chloride.
