A basic solution contains the iodide and phosphate ions that are to be separated

Question

A basic solution contains the iodide and phosphate ions that are to be separated via selective precipitation.
The I– concentration, which is 9.20×10-5 M, is 10,000 times less than that of the PO43– ion at 0.920 M .
A solution containing the silver(I) ion is slowly added. Answer the questions below.

Ksp of AgI is 8.30×10-17 and of Ag3PO4, 8.90×10-17.

Part 1 (0.3 point) See Periodic Table Calculate the minimum Ag concentration required to cause precipitation of Agl mo/L Part 2 (0.3 point) Calculate the minimum Ag" concentration required to cause precipitation of Ag3PO4 molVL Part 3 (0.3 point) Which salt will precipitate first? Choose one: Agl Cannot be determined. Part 4 (0.3 point) Is the separation of the l-and PO43-ion complete (is the percentage of "remaining" ion less than 0.10% or its original value? Choose one: Yes No Cannot be determined

Explanation / Answer

Part 1:

Ksp of AgI = 8.3*10^-17 = [Ag+] [I-]

[I-] = 9.20×10^-5

8.3*10^-17 = [Ag+] [I-]

[Ag+] = 8.3*10^-17 / 9.20×10^-5 = 9.02*10^-13 M

9.02*10^-13 M is the concetration of Ag+ needed for precipitation

2]

Ksp of Ag3PO4 = 8.9*10^-17 = [Ag+]^3 [PO4-3]

[Ag+] = 8.9*10^-17 / (0.92)^3

[Ag+]= 1.143*10^-16 M

THis much concentration of Ag+ is needed for precipitation

3]

From the above 2 answers

for Ag3PO4 needed to precipitate we need less amount of Ag+ concentration than for AgI precipitation

So Ag3PO4 precipitates first

4]

No

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