Answer:
47 kJ·mol⁻¹
Explanation:
NaI(s) ⟶ Na⁺(aq) + I⁻(aq); ΔH = ?
We can carry out this process in a series of steps.
1. Convert the solid to its gaseous ions.
NaI(s) ⟶ Na⁺(g) + I⁻(g); -ΔH(lat) = 704 kJ
2. Hydrate the Na⁺ ions
Na⁺(g) ⟶ Na⁺(aq); ΔH(hyd) = - 410.0 kJ
3. Hydrate the I⁻ ions
I⁻(g) ⟶ I⁻(aq); ΔH(hyd) = -247
4. Add the equations
Cancel ions that occur on opposite sides of the reaction arrow
ΔH/kJ·mol⁻¹
NaI(s) ⟶ Na⁺(g) + I⁻(g); +704
Na⁺(g) ⟶ Na⁺(aq); - 410.0
I⁻(g) ⟶ I⁻(aq); -247
NaI(s) ⟶ Na⁺(g) + I⁻(g) 47
The heat of solution of NaI is 47 kJ·mol⁻¹.