Given, $$E_{A{g^ + }|Ag}^0 = 0.799$$ (at 298 K) and K_sp of $$AgI = 8.7 \times {10^{ - 17}}$$

In a saturated solution of AgI, [Ag⁺] = [I^$$-$$]

$$\therefore$$ $$[A{g^ + }] = \sqrt {{K_{sp}}} = \sqrt {8.7 \times {{10}^{ - 17}}} = 9.33 \times {10^{ - 9}}$$

According to Nernst equation of $$A{g^ + } + e \to Ag(s)$$

$$\therefore$$ $$E_{A{g^ + }|Ag}^{} = E_{A{g^ + }|Ag}^0 - {{0.059} \over n}\log {1 \over {[A{g^ + }]}}$$

or, $$E_{A{g^ + }|Ag}^{} = 0.799 - {{0.059} \over 1}\log {1 \over {[A{g^ + }]}}$$

or, $$E_{A{g^ + }|Ag}^{} = 0.799 - 0.059\log {1 \over {9.33 \times {{10}^{ - 9}}}}$$

$$\therefore$$ $$E_{A{g^ + }|Ag}^{} = 0.325$$ V

The relation between $$E_{{I^ - }|AgI|Ag}^0$$ and $$E_{A{g^ + }|Ag}^0$$ is

$$E_{{I^ - }|AgI|Ag}^0 = E_{A{g^ + }|Ag}^0 + 0.059\log {K_{sp}}$$

$$\therefore$$ $$E_{{I^ - }|AgI|Ag}^0 = 0.799 + 0.059\log (8.7 \times {10^{ - 17}}) = - 0.148$$ V