Determine the overall change in energy for the formation of solid cesium sulfide from gaseous cesium and sulfur, knowing that the lattice of CsS = -3.470 aJ.

Data:

I₁(Cs) = 0.623 aJ

EA1(S) = - 0.332 aJ

EA₂(S) = + 0.980 aJ

d_MgS= 351 pm

Coulomb constant = 231 aJ.pm

Question

Determine the overall change in energy for the formation of solid cesium sulfide from gaseous cesium and sulfur, knowing that the lattice of CsS = -3.470 aJ.

Data:

I₁(Cs) = 0.623 aJ

EA1(S) = - 0.332 aJ

EA₂(S) = + 0.980 aJ

d_MgS= 351 pm

Coulomb constant = 231 aJ.pm

| General Chemistry 1

Accepted Answer

Chemical equation: 2 Cs (g) + S (g) → Cs₂S (s)

First step: Cs (g) → Cs⁺ (g) + e^-

Second step:
S(g) + e^- → S^- (g)
S^- (g) + e^- → S^2- (g)

E_reaction = 2 x I₁(Cs) + EA₁(S) + EA₂(S) + E_lattice = -1.576 aJ

We do not use the coulomb energy since the final compound is a solid and not a gas of an ionic compound.

Final - Question 8 | General Chemistry 1

General Chemistry 1 - Final