Struggling on these 3 questions for chem and need help?

Question

1. The Ksp Of lanthanum iodate, La(IO3)3, is 7.50 × 10^-12. Calculate the molar solubility, x, of this compound. Answer in M.
2. A solution contains 0.0460 M Ca^2+ and 0.0910 M Ag^+. When the second cation just starts to precipitate, what percentage of the first cation remains in solution? Answer in %.
3. A solution containing a mixture of metal cations was treated as follows.
4. Dilute HCl was added and a precipitate formed. The precipitate was filtered off.
5. H2S was bubbled through the acidic solution. Again, a precipitate formed and was filtered off.
6. The pH was raised to about 9 and H2S was again bubbled through the solution. No precipitate formed.
7. Finally, sodium carbonate was added and no precipitate formed.
8. What can be said about the presence of each of these groups of cations in the original solution?

Cation Group	Description	Present in the original solution?
Ag^+, Pb^2+, Hg^2+	form insoluble chlorides
Bi^3+, Cd^2+, Cu^2+, Hg^2+, Pb^2+, Sb^3+, Sn^2+, Sn^4+	form acid-insoluble sulfides
Al^3+, Co^2+, Cr^3+, Fe^2+, Fe^3+, Ni^2+, Mn^2+, Zn^2+	form base-insoluble sulfides or hydroxides
Ba^2+, Ca^2+, Mg^2+, Sr^2+	form insoluble carbonates
Li^+, Na^+, K^+, NH4^+	completely soluble

1. Word Bank (for “Present in the Original Solution” section):
2. All of these ions were present.
3. None of these ions were present.
4. At least one of these ions was present.
5. Unknown.

Answer 1

Arisa,

There is a lot of material here. I will get you started but you may want to submit these as separate questions. You are likely to get more answers that way.

1.) The Ksp Of lanthanum iodate, La(IO₃)₃, is 7.50 × 10^-12. Calculate the molar solubility, x, of this compound. Answer in M.

La(IO₃)₃(s) <==> La³⁺(aq) + 3 IO₃^-(aq) .. dissolution reaction

Ksp = [La³⁺][IO₃^-]³

Let x = [La³⁺], then [IO₃^-] = 3x

Ksp = 7.50x10^-12 = (x)(3x)³

7.50x10^-12 = 27x⁴

x⁴ = 2.78x10^-13

x = 7.26x10^-4 M = [La³⁺] = molar solubility of La(IO₃)₃

2.) A solution contains 0.0460 M Ca²⁺ and 0.0910 M Ag⁺. When the second cation just starts to precipitate, what percentage of the first cation remains in solution? Answer in %.

Not sure we can answer this without knowing what else is being added to the solution in order to cause a precipitate to form. We would also need the Ksp for the Ca and Ag salts of this particular precipitate.