Question

Lithium iodide has a lattice energy of -7.3 x 102(kj/mol) and a heat of hydration of -793 kj/mol. find the heat of solution for lithium iodide and determine how much heat is evolved or absorbed when 15.0 g of lithium iodide completely dissolves in water.

Answer 1

Given molecule Lithium iodide (LiI)

Heat of hydration = -793 kj/mol

Lattice energy = -730 kJ/mol

Heat of hydration = Heat of solution - Lattice energy

Heat of solution = Hydration + Lattice = -793 + (- 730) = -1523 kJ/mol

Now,

Mass of LiI = 15.0 g

molar mass of LiI = 134 g/mol

# moles of LiI = 15/134 = 0.112 moles

Heat of solution for 1 mole of LiI = -1523 KJ

Therefore, for 0.112 moles of LiI the corresponding heat is

= 0.112 *(-1532) = 171.6 kJ