Given that the first and second electron affinities of sulfur are −0.332 aJ and +0.980 aJ, the ionic radii of Zn2+ and S2− are 74 pm and 184 pm, and
Zn(g)⟶Zn2+2e- 𝐸=4.38 aJ
calculate the energy change for the following reaction (per formula unit of ZnS).
Zn(g)+S(g)⟶ZnS(g)
Well, let's break it down.
First, we need to calculate the energy change for Zn(g) to Zn2+:
ΔE = Zn2+ - Zn
= [(2 × (−0.332 aJ) + (+0.980 aJ)]
Now, we also need to consider the energy change for S(g) to S2-:
ΔE = S2- - S
= [(−0.980 aJ) - (−0.332 aJ)]
Now, to find the energy change for the reaction Zn(g) + S(g) ⟶ ZnS(g), we need to add up the individual energy changes:
ΔE = (−0.980 aJ) + (−0.332 aJ) + (+0.980 aJ)
Now, I must say, these energy values are so small, they make me feel aJnry. But don't worry, I'm here to shed some light on their meaning.
To calculate the energy change for the reaction (per formula unit of ZnS), we need to consider the formation of Zn2+ and S2- ions separately, as well as the formation of the ZnS compound.
1. Formation of Zn2+ ions:
Zn(g) ⟶ Zn2+ + 2e- E = +4.38 aJ
2. Formation of S2- ions:
S(g) + 2e- ⟶ S2- E = +0.332 aJ (reverse sign)
3. Formation of ZnS compound:
Zn2+ + S2- ⟶ ZnS ?
To find the energy change for the formation of ZnS, we need to add the energy changes for the two ion formations:
ΔH = ΔH(Zn2+) + ΔH(S2-)
ΔH(Zn2+) = +4.38 aJ (given)
ΔH(S2-) = -0.332 aJ (from the first electron affinity of sulfur)
ΔH = 4.38 aJ + (-0.332 aJ)
ΔH = 4.712 aJ
Therefore, the energy change for the reaction (per formula unit of ZnS) is +4.712 aJ.
To calculate the energy change for the reaction Zn(g) + S(g) ⟶ ZnS(g), we need to find the sum of the energy changes for the formation of Zn2+ and S2- ions from their respective atoms. Then, we can subtract the energy change for the formation of ZnS from these individual energy changes to get the overall energy change.
1. Formation of Zn2+ from Zn(g):
Zn(g) ⟶ Zn2+(g) + 2e-
Energy change = -4.38 aJ (Given)
2. Formation of S2- from S(g):
S(g) + 2e- ⟶ S2-(g)
Energy change = -0.332 aJ (First electron affinity of sulfur) + 0.980 aJ (Second electron affinity of sulfur)
3. Formation of ZnS from Zn2+ and S2-:
Zn2+(g) + S2-(g) ⟶ ZnS(g)
To calculate this energy change, we can use the Born-Haber cycle or the lattice energy concept. However, the required data (such as lattice energy and enthalpy of formation) are not provided.
Without the necessary data, we cannot directly calculate the energy change for the formation of ZnS. To obtain the exact energy change, additional information or experimental data is required.
Note: The energy change for a reaction is dependent on various factors, such as bond strength, lattice energy, enthalpy of formation, etc.