Exercise $6.$ Calculate $K_c$ for the following reactions at $25C$ :

a$)Mg(s)+P{b}^{2+}(aq)M{g}^{2+}(aq)+Pb(s)$

b$)B{r}_2(l)+2I^{-}(aq)2B{r}^{-}(aq)+I_2(s)$

c$)O_2(g)+4H^{+}(aq)+4F{e}^{2+}(aq)2H_{2}O(l)+4F{e}^{3+}(aq)$

d$)2Al(s)+3I_2(s)2A{l}^{3+}(aq)+6I^{-}(aq)$