Question

Silver ion is being considered as a reagent for separating 1037 from CO3 in a solution that is 0.060 M in K2CO3 and 0.070 M in Nalo. Which anion will precipitate first when silver ion is added to the solution and what will its concentration be when the second anion begins to precipitate? Can the two ions be separated with 99.99% efficiency? (6pts) Ksp = 3.1 x 10-8 for Ag103 Ksp = 8.1 x 10-12 for AgaCO3

Answer 1

i)

Solubility equilibrium of AgIO3 is

AgIO3(s) <-------> Ag⁺(aq) + IO3^-(aq)

Ksp = [Ag⁺] [IO3^-] = 3.1×10^-8

[Ag⁺] × 0.070M= 3.1 ×10^-8M²

[Ag⁺]= 4.43 × 10^-7M

Therefore,

minimum concentration of Ag⁺ required to start precipitate IO3^- is 4.43 ×10^-7M

solubility equilibrium of Ag2CO3

Ag2CO3(s) <-------> 2Ag⁺(aq) + CO3^2-(aq)

Ksp = [Ag⁺]²[CO3^2-] = 8.1×10^-12

[Ag⁺]²× 0.060M = 8.1 ×10^-12M³

[Ag⁺]² = 1.33×10^-10M²

[Ag⁺] = 1.15 × 10^-5M

minimum concentration of Ag⁺ required to start precipitate of CO3^2- is 1.15 ×10^-5M

IO3^- ​​​​​​ion require low concentration of Ag⁺ ​​​​​​

Therefore,

IO3^- would precipitate first

ii)

Substitute the concentration Ag⁺ required start precipitate CO3^2- in Ksp expression of AgIO3

[Ag⁺][IO3^-] = 3.1 ×10^-8

1.15 ×10^-5 M × [IO3^-] = 3.1 ×10^-8M²

[IO3^-] = 2.70× 10^-3M

Therefore,

Concentration of IO3^- when CO3^2- start to precipitate =

2.70 × 10^-3M

iii)

℅ of IO3^- remaining when CO3^2- start to precipitate = (0.00270M/0.070M)× 100 = 3.86%

Therefore

these two ions can not be seperated with 99.99% efficiency