Exercise 9 | Ionic Bonds and Compounds

Calculate the energy of the following reaction:

Na (g) + Br (g) → NaBr (g)


Data:

I1 (Na) = 0.824 aJ

EA1 (Br) = -0.540 aJ

rNa+ = 102 pm

rBr- = 196 pm

First step:

Na (g) → Na+ (g) + 1 e-

Energy = I1 = 0.824 aJ


Second step:
Br (g) + 1 e- → Br- (g)

Energy = EA1 = -0.540 aJ


Third step:

Na+ (g) + Br- (g) → NaBr (g)

Energy = Ecoulomb = 231 x +1-1298 = -0.775 aJ


Energy of reaction: E = 0.824 – 0.540 – 0.775 = -0.491 aJ