Question

If an electric current is passed through aqueous solutions of sodium chloride, sodium bromide, and sodium iodide, the elemental halogens are produced at one electrode in each case, with hydrogen gas being evolved at the other electrode. If the liquid is then evaporated from the mixture, a residue of sodium hydroxide remains. Write balanced chemical equations for these electrolysis reactions.

Short answer

The balanced chemical equations for the electrolysis reactions are: 1. Sodium Chloride: \(2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)\) 2. Sodium Bromide: \(2NaBr(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Br_2(g) + H_2(g)\) 3. Sodium Iodide: \(2NaI(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + I_2(g) + H_2(g)\)

Step-by-step solution

Reaction 1: Electrolysis of Sodium Chloride (NaCl)

We'll start with the electrolysis of NaCl. The half-reactions are 1. Oxidation: \(2Cl^-(aq) \rightarrow Cl_2(g) + 2e^-\) 2. Reduction: \(2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)\) Now, we will combine both half-reactions. \(2Cl^-(aq) + 2H_2O(l) \rightarrow Cl_2(g) + H_2(g) + 2OH^-(aq)\) The balanced chemical equation for the electrolysis of sodium chloride is \(2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)\)

Reaction 2: Electrolysis of Sodium Bromide (NaBr)

Now let's move onto the electrolysis of NaBr. The half-reactions are 1. Oxidation: \(2Br^-(aq) \rightarrow Br_2(g) + 2e^-\) 2. Reduction: \(2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)\) Now, we will combine both half-reactions. \(2Br^-(aq) + 2H_2O(l) \rightarrow Br_2(g) + H_2(g) + 2OH^-(aq)\) The balanced chemical equation for the electrolysis of sodium bromide is \(2NaBr(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Br_2(g) + H_2(g)\)

Reaction 3: Electrolysis of Sodium Iodide (NaI)

Finally, let's analyze the electrolysis of NaI. The half-reactions are 1. Oxidation: \(2I^-(aq) \rightarrow I_2(g) + 2e^-\) 2. Reduction: \(2H_2O(l) + 2e^- \rightarrow H_2(g) + 2OH^-(aq)\) Now, we will combine both half-reactions. \(2I^-(aq) + 2H_2O(l) \rightarrow I_2(g) + H_2(g) + 2OH^-(aq)\) The balanced chemical equation for the electrolysis of sodium iodide is \(2NaI(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + I_2(g) + H_2(g)\) In summary, we have written the balanced chemical equations for the electrolysis reactions of sodium chloride, sodium bromide, and sodium iodide.