Identify in simple electrolytic cells: (a) the anode as the positive electrode (b) the cathode as the negative electrode (c) the electrolyte as the molten or aqueous substance that undergoes electrolysis

Electrochemistry – Electrolysis

Key Concepts

  • Electrolysis: using electricity to drive a non‑spontaneous reaction.

  • Electrolyte: molten or aqueous substance that conducts electricity.

  • Anode: positive electrode where oxidation occurs.

  • Cathode: negative electrode where reduction occurs.

Analogy: The Electrolytic Cell as a Playground ⚽️

Imagine the electrolyte as a playground where ions (kids) can move freely. The anode is the “red zone” where kids lose their toys (oxidation). The cathode is the “blue zone” where kids gain toys (reduction). The electric current is like a referee pushing kids from one zone to the other.

How to Identify the Electrodes

  1. Look at the electrode’s sign: + → anode, – → cathode.

  2. Check the reaction: oxidation (loss of electrons) at the anode, reduction (gain of electrons) at the cathode.

  3. Remember the mnemonic: “Anode is Positive, Cathode is Negative” (APCN).

Example: Electrolysis of Molten NaCl 🔥

In molten sodium chloride, the reactions are:

ElectrodeReactionProducts
Anode (positive)\$2Cl^- \rightarrow Cl_2 + 2e^-\$\$Cl_2\$ gas
Cathode (negative)\$2Na^+ + 2e^- \rightarrow 2Na\$\$Na\$ metal

Exam Tips 📚

Tip 1: Write the electrode symbol (+ or –) before the name.

Tip 2: Use the mnemonic “Anode is Positive, Cathode is Negative” to avoid confusion.

Tip 3: Remember that the electrolyte is the substance that actually moves ions; the electrodes are just where the reactions happen.

🧪 Good luck!

Quick Quiz ❓

Which electrode is the anode in the electrolysis of aqueous \$\ce{CuSO4}\$? ⚡️

  • • The electrode where \$\ce{Cu^{2+}}\$ is reduced to copper metal.

  • • The electrode where \$\ce{H2O}\$ is oxidised to oxygen gas.

  • • The electrode where \$\ce{Cu^{2+}}\$ is oxidised to copper ions.

Answer: The anode is the electrode where \$\ce{H2O}\$ is oxidised to \$\ce{O2}\$ (positive electrode). The cathode is where \$\ce{Cu^{2+}}\$ is reduced to copper metal.