What is the solubility product of CaF2 if 0.1 M Ca2+ and 0.02 M F- are in solution just before precipitation occurs?
4.0 × 10^-5
The solubility product cannot be determined.
1.6 × 10^-4
2.0 × 10^-3
It's 4.0 × 10^-5
To determine the solubility product of CaF2, we need to set up the balanced equation for the dissolution of CaF2:
CaF2(s) ⇌ Ca2+(aq) + 2F-(aq)
The solubility product expression for CaF2 is given by:
Ksp = [Ca2+][F-]^2
We are given the initial concentrations of Ca2+ and F- just before precipitation occurs:
[Ca2+] = 0.1 M
[F-] = 0.02 M
Substituting these values into the solubility product expression, we get:
Ksp = (0.1)(0.02)^2
Ksp = 0.1 × 0.04
Ksp = 0.004
Therefore, the solubility product of CaF2 is 0.004 or 4.0 × 10^-3. None of the answer choices match this value, so the correct answer is "The solubility product cannot be determined."
To determine the solubility product of CaF2, we need to use the concentrations of the ions present just before precipitation occurs. The solubility product (Ksp) expression for CaF2 is:
CaF2(s) ⇌ Ca2+(aq) + 2F-(aq)
The given concentrations are 0.1 M for Ca2+ and 0.02 M for F-. Since CaF2 is a sparingly soluble salt, it will form a precipitate when the product of the ion concentrations exceeds the solubility product.
In this case, the concentrations of Ca2+ and F- will be used to calculate the ionic product (Qsp) just before precipitation. Qsp is calculated as the product of the ion concentrations raised to the power of their stoichiometric coefficients:
Qsp = [Ca2+] * [F-]^2
Substituting the given concentrations:
Qsp = 0.1 * (0.02)^2 = 0.1 * 0.0004 = 0.00004
Comparing Qsp to the solubility product, we have:
Qsp < Ksp
Therefore, the solubility product of CaF2 is greater than 0.00004. Among the given options, 4.0 × 10^-5, 1.6 × 10^-4, and 2.0 × 10^-3, the closest value to this comparison is 1.6 × 10^-4.
Therefore, the correct answer is 1.6 × 10^-4.
.....................CaF2 ==> Ca^2+ + 2F^-
Write the Ksp expression for CaF2, the problem gives you the value for Ca^2+ and for F^-, cubstitute those values and solve for Kp. NOTE: The problem tells you that the (F^-) is 0.02M. Do NOT mutiply that by 2.