Final answer:
Molar solubility (s) of MX in pure water is calculated by solving the equation s2 = Ksp, while in solutions with common ions, the solubility is reduced and requires adjusting the calculation to account for the shift in equilibrium.
Step-by-step explanation:
Calculating Molar Solubility from Ksp
For a compound MX which dissociates into M+ and X-, the solubility product constant (Ksp) can be expressed as Ksp = [M+][X-] = s2, where s is the molar solubility of MX in pure water. Given that Ksp = 1.27 × 10⁻³⁶, to find the molar solubility (s) we set up the equation s2 = 1.27 × 10⁻³⁶ and solve for s.
In pure water, the calculation is straightforward as there are no other sources of ions. However, in the presence of common ions as in 0.25 M MCl2, 0.20 M Na2X, or 0.10 M MX, the solubility will change due to the common ion effect, reducing the solubility of MX.
To calculate the molar solubility in the presence of a common ion, we must adjust the Ksp equation to account for the increased concentration of the common ion, which in turn shifts the equilibrium and reduces the molar solubility of MX.