Please show all work, note that there are two problems that are independent of o

Question

Please show all work, note that there are two problems that are independent of one another. THANK YOU!

1.) What is the solubility of lead chloride (PbCl2) in 0.505 M NaCl (aq)? The Ksp of PbCl2 = 2.4 x 10-4.

2.) If 0.20 M NaOH was added dropwise to a solution containing 0.35 M Ca(NO3)2 and 0.50 M Fe(NO3)2, which would precipitate first, Ca(OH)2 or Fe(OH)2 ? The Ksp of Ca(OH)2 = 8 x 10-6 and the Ksp of Fe(OH)2 = 1.6 x 10-14. Justify your answer by giving the maximum hydroxide concentration for both Ca2+ and Fe2+ before precipitation would begin. Be sure to show your work.

Explanation / Answer

1.)Ksp = [Pb2+][Cl-]^2

2.4 x 10^-4 = s*(2s+0.505)^2

Since s<<0.505

s*(0.505)^2 = 2.4 x 10^-4

So s = 9.41 x 10^-4 M

2.) Ksp = [Ca2+][OH-]^2

8 x 10^-6 = (s+0.35)(2s)^2

Since s<<0.35

8 x 10^-6 = 0.35*(2s)^2

So s = 2.39 x 10^-3

[OH-]= 2s = 4.78 x 10^-3 M

Ksp = [Fe2+][OH-]^2

1.6 x 10^-14 = (s+0.5)(2s)^2

Since s<<0.5

1.6 x 10^-14 = 0.5*(2s)^2

So s = 8.94 x 10^-8

[OH-]= 2s = 1.78 x 10^-7 M

So [OH-] required for Fe(OH)2 is less.

So Fe(OH)2 would precipitate first.

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