Answer
$K_{sp} = [Hg^{2+}][I^-]^2$
Work Step by Step
1. Identify the ions, and write the equilibrium reaction for the dissociation of the salt $(HgI_2)$:
- $Hg^{2+}$ and $I^-$
- $HgI_2(s) \lt -- \gt Hg^{2+}(aq) + I^-(aq)$
2. Balance the reaction:
- $1HgI_2(s) \lt -- \gt 1Hg^{2+}(aq) + 2I^-(aq)$
3. Write the $K_{sp}$ expression:
- Multiply the concentrations of the ions.
- The balancing coefficients are used to determine the exponents of the concentrations.
- $K_{sp} = [Hg^{2+}]^1 \times [I^-]^2$
