Use the data given below to construct a Born - Haber cycle to determine the electron affinity of Br?

Question

DH°(kJ)
K(s) → K(g) 89
K(g) → K⁺(g) + e⁻ 419
Br2(l) → 2 Br(g) 193
K(s) + 1/2 Br2(g) → KBr (s) -394
KBr(s) → K⁺(g) + Br⁻(g) 674

I know the answer is -325 kj, I want to know how to get it. Thanks

Answer 1

sub = sublimation
ip =- ionization potential
DE = dissociation energy
EA = electron affinity
Hf = heat formation
Ecrystal = reverse last equation
dHf = dHsub + ip + 1/2(DE) + EA + Ecryst
-394 = 89+419+96.5+EA-674
Solve for EA.