First, perhaps a simpler way to do 1 would be to assume that the reaction goes to completion and then do the reverse.
Pb
2+ + 2F
- PbF
2Assume that this goes to completion, but also note that Pb
2+ is the limiting reactant, and thus, there is 0.10 M of F
- left. Now write the reverse reaction, and do Ksp, except that the "initial" concentration of F
- is 0.10, not 0.
PbF
2 Pb
2+ + 2F
-I 0 0.10
C +x +2x
E x 0.10 +2x
Set Ksp up, but you can assume that 2x <<<< 0.10, and drop that term.
Then the math becomes really easy.
2 is the same as 1, except we are talking about Kformation rather than Ksp. The math is slightly tougher because in Ksp, the solid doesn't appear in the equilibrium constant, but in 2, [Zn(NH
3)
4]
2+ does. I would use the above method of assuming the reaction goes to completion, then doing the calculations for the reverse reaction.
For 3, you first need to figure out the equilibrium [Ag
+]. Then I suppose you need Ksp for AgCl.