<P> where E is the standard electrode potential for the reaction and a is the activity for the mercury cation (the activity for a liquid of 1 Molar is 1). </P> <P> At equilibrium,: Δ G = − n F E = 0 J / m o l (\ displaystyle \ Delta G = - nFE = 0 \ mathrm (J / mol)), or equivalently E cell = 0 V (\ displaystyle E_ (\ text (cell)) = 0 \ \ mathrm (V)). This equality allows us to find the solubility product . </P> <Dl> <Dd> E cell = E Hg 2 Cl 2 / Hg 2 2 +, Cl − 0 − R T 2 F ln ⁡ 1 (Hg 2 2 +) ⋅ (Cl −) 2 = + 0.53 + R T 2 F ln ⁡ k s p = 0 V (\ displaystyle E_ (\ text (cell)) = E_ ((\ ce (Hg2Cl2 / Hg2 ^ 2 +, Cl -))) ^ (0) - (\ frac (RT) (2F)) \ ln (\ frac (1) ((\ ce ((Hg2 ^ 2 +))) \ cdot (\ ce ((Cl ^ -))) ^ (2))) = + 0.53 + (\ frac (RT) (2F)) \ ln (k_ (sp)) = 0 \ \ mathrm (V)) </Dd> <Dd> ln ⁡ k s p = − 0.53 ⋅ 2 F R T (\ displaystyle \ ln (k_ (sp)) = - 0.53 \ cdot (\ frac (2F) (RT))) </Dd> <Dd> k s p = e − 0.53 ⋅ 2 F R T = 1.184 × 10 − 18 (\ displaystyle k_ (sp) = e ^ (- 0.53 \ cdot (\ frac (2F) (RT))) = 1.184 \ times 10 ^ (- 18)) </Dd> <Dd> k s p = (Hg 2 2 +) ⋅ (Cl −) 2 = 1.184 × 10 − 18 (\ displaystyle k_ (sp) = (\ ce ((Hg2 ^ 2 +))) \ cdot (\ ce ((Cl ^ -))) ^ (2) = 1.184 \ times 10 ^ (- 18)) </Dd> </Dl> <Dd> E cell = E Hg 2 Cl 2 / Hg 2 2 +, Cl − 0 − R T 2 F ln ⁡ 1 (Hg 2 2 +) ⋅ (Cl −) 2 = + 0.53 + R T 2 F ln ⁡ k s p = 0 V (\ displaystyle E_ (\ text (cell)) = E_ ((\ ce (Hg2Cl2 / Hg2 ^ 2 +, Cl -))) ^ (0) - (\ frac (RT) (2F)) \ ln (\ frac (1) ((\ ce ((Hg2 ^ 2 +))) \ cdot (\ ce ((Cl ^ -))) ^ (2))) = + 0.53 + (\ frac (RT) (2F)) \ ln (k_ (sp)) = 0 \ \ mathrm (V)) </Dd>

Preparation of saturated calomel electrode and determination of standard potentials of electrodes