During the electrolysis of aqueous NaBr, what is produced at the cathode and at the anode?

• A. Sodium metal at the cathode and bromine gas at the anode
• B. Sodium metal at the cathode and oxygen gas at the anode
• C. Hydrogen gas at the cathode and oxygen gas at the anode
• D. Hydrogen gas at the cathode and bromine gas at the anode

Answer: (D)

Verified step by step guidance

1. Identify the species present in the aqueous NaBr solution: Na\textsuperscript{+}, Br\textsuperscript{-}, H\textsubscript{2}O molecules, and possibly H\textsuperscript{+} and OH\textsuperscript{-} from water dissociation.
2. At the cathode (reduction site), compare the reduction potentials of Na\textsuperscript{+} and H\textsuperscript{+} (from water). Since water is more easily reduced than Na\textsuperscript{+}, hydrogen gas (H\textsubscript{2}) is produced instead of sodium metal.
3. At the anode (oxidation site), compare the oxidation potentials of Br\textsuperscript{-} and water. Bromide ions are more easily oxidized than water, so bromine gas (Br\textsubscript{2}) is produced at the anode.
4. Write the half-reactions for each electrode: Cathode (reduction): \$2\mathrm{H^{+}} + 2e^{-} \rightarrow \mathrm{H_2(g)}$ Anode (oxidation): \$2\mathrm{Br^{-}} \rightarrow \mathrm{Br_2(g)} + 2e^{-}$
5. Combine the half-reactions to understand the overall electrolysis process, confirming that hydrogen gas forms at the cathode and bromine gas forms at the anode during the electrolysis of aqueous NaBr.