Question

1. Write the chemical equation for the formation of KCl (s)

2. Write the chemical equation describing the lattice energy for KCl (s)

Answer 1

KCl --> elements are K and Cl

standard state for K --> K(s)

standard state for Cl --> Cl2(g)

then

K(s) + Cl2(g) --> KCl(s)

balnace

K(s) + 1/2Cl2(g) --> KCl(s)

Q2.

The Lattice energy can be calculated via:

dHf = dHsub + IE + dH(X-X) + EA + U

where U is the value of interest

list:

Heat of formation = (energy required to form element)

Het of atomization = (energy from solid to gas)

Dissociation Energy = (energy required to split X2 to 2X)

Sum of ionization energes = IE1(M)

Sum of Electorn affinites (of the nonmetal, X) = EA(X)

Then

substitute

Lattice energy= Heat of formation- Heat of atomization- Dissociation energy- (sum of Ionization energies)- (sum of Electron Affinities)

dHf = dHsub + IE + dH(X-X) + EA + U

U = dHf - (dHsub + IE(M) + dH(X-X) + EA)