Find Ksp given electrochem data

Question

I really need a solved answer I could see last person I asked didnt do that. This is extra credit my whole assignment is worth two points and I have 30 questions (do the math). Im not asking for answers just help. Its not A but D is the answer.

Calculate the solubility product of silver iodide at 25°C given the following data:

E˚(V)

AgI(s) e– → Ag(s) I– –0.15

I2(s) 2e– → 2I– 0.54

Ag e– → Ag(s) 0.80

A. 2.9 × 10–3

B. 1.9 × 10–4

C. 2.1 × 10–12

D. 9.0 × 10–17

E. 2.4 × 10–24

Answer 1

no,it is D.

Ag e– → Ag(s) 0.80

AgI(s) e– → Ag(s) I– –0.15

this cell: E=0.95,standard cond.1M for Ag+ and I-

net result: (Ag+)+( I-)>AgI(s)

it is driven solely by precipitation:

Ecell (25C) = -(0.0592/n)(logK) ,it has a minus!!!!

10^-(0.950/0.0592)=10^-16.05=9.10^-17

Answer 2

You need to add equations 1 and 3 as follows:

AgI(s) + e– → Ag(s) +  I– –0.15

Ag(s) → Ag+ + e– –0.80

This gives you the correct Ksp expression, which is:

AgI(s) --->  Ag+ + I–

You had the wrong chemical equation. Put the answer (-0.95 V) into the Ecell equation and you will recover answer D.