Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

1) A solution contains 5.72×10-3 M manganese(II) nitrate and 6.51×10-3 M lead ac

ID: 552447 • Letter: 1

Question

1) A solution contains 5.72×10-3 M manganese(II) nitrate and 6.51×10-3 M lead acetate. Solid ammonium carbonate is added slowly to this mixture. What is the concentration of lead ion when manganese(II) ion begins to precipitate? [Pb2+] ____= M

2) A solution contains 9.10×10-3 M potassium hydroxide and 1.41×10-2 M potassium cyanide.  
Solid zinc acetate is added slowly to this mixture.  

What is the concentration of hydroxide ion when cyanide ion begins to precipitate?  
[hydroxide] = ___M

*** I'm stuck on both, please help***

Explanation / Answer

1)

Ksp of MnCO3 = 2.24×10–11

Ksp of PbCO3 = 7.40×10–14

MnCO3   --------------> Mn+2   +   CO32-

Ksp = [Mn+2][CO32-]

2.24×10–11 = (5.72 x 10^-3) [CO32-]

[CO32-] = 3.92 x 10^-9 M

PbCO3 ------------> Pb+2 + CO32-

Ksp = [Pb+2][CO32-]

7.40×10–14 = [Pb+2] (3.92 x 10^-9 )

[Pb+2] = 1.89 x 10^-5 M