For electrolysis, state general observations.

• A. The bulb will light, a metal is formed on the cathode, fizz of gases produced.
• B. Only color changes occur at the electrodes.
• C. No visible changes occur.
• D. Only heat is produced.

Answer: (A)

Electrolysis shows visible signs of both electrical current and chemical changes at the electrodes. The fact that the bulb lights indicates current is flowing through the electrolyte. At the cathode, reduction occurs and metal ions in the solution can be deposited as a solid metal, so you may see a metal layer forming there. At the same time, the electrolyte often releases gases at the electrodes, seen as fizz or bubbles—hydrogen gas typically forms at the cathode and oxygen (or other gases depending on the electrolyte) forms at the anode. So, general observations are a working circuit (bulb lights), metal deposition on the cathode, and gas bubbles at the electrodes. The exact products depend on the electrolyte and electrodes, and sometimes heat is produced, but the most characteristic clues are the light in the circuit, deposition at the cathode, and fizz from gas evolution.