In an electrolysis setup, what happens at the cathode?

• A. A metal is formed on the cathode
• B. A gas is formed at the cathode
• C. The solution changes color
• D. The electrolyte evaporates

Answer: (A)

At the cathode, reduction occurs: positively charged ions in the electrolyte move to the negatively charged electrode and gain electrons. If these ions are metal ions, they become neutral metal atoms and deposit onto the cathode. That deposition is what the option describes. Gas formation at the cathode can happen only if the species reduced is a gas-forming ion (for example, hydrogen from H+ reduction), but in a typical electrolysis of metal salts the main event is metal deposition on the cathode. The other options—the solution changing color or the electrolyte evaporating—aren’t general results of the cathode reaction.