Question

Write the equations representing the lattice energy reaction and the five main equations that need to be combined to obtain the lattice energy for CrCl3. Show how the five equations are combined to give the lattice energy equation. You can combine the multiple ionization energy steps for Cr into one net ionization energy reaction.

Answer 1

Ans For lattice energy we need to Cr to Cr3+(g) and Cl3 to 3Cl-(g).

1. Sublimation of Cr:- Cr(s) = Cr(g)

2. 3 times Ionization of Cr:- Cr(g) - 3e = Cr3+(g)

3. enthalpy of atomization of Cl:- Cl3 = 3Cl(g)

4. electron affinity of Cl(g):- 3Cl(g) + 3e = 3Cl-(g)

5. Both will combine to form:- Cr3+(g) + 3Cl-(g) = CrCl3

Heat of formation = Sublimation energy + I.E1 + I.E2 + I.E3 - Ea1 - Ea2 + dissociation - lattice energy

All value to be put in +ve because for -negative value already put -ve sign before parameter