The common feature of reactions at the anode is that

Analyze the question: It asks what is always true (the "common feature") of reactions at the anode, whether in an electrolytic cell or a galvanic (electrochemical) cell.

Concept: The anode is defined as the electrode where oxidation occurs. Remember the mnemonic AN OX (ANode = OXidation) and RED CAT (REDuction = CAThode).

Oxidation means loss of electrons, for example:

• Cu → Cu²⁺ + 2e⁻ (a copper anode dissolves)
• 2Cl⁻ → Cl₂ + 2e⁻ (chloride ions discharge, and no electrode dissolves)
• 4OH⁻ → 2H₂O + O₂ + 4e⁻

Checking each option:

• A. Electrons are consumed. Wrong. Electrons are released at the anode. They are consumed at the cathode.
• B. Ions are reduced. Wrong. Reduction of ions happens at the cathode.
• C. Oxidation is involved. Correct. Every anode reaction involves loss of electrons, whether it is a metal atom or an anion being oxidized.
• D. The electrode dissolves. Not always true. With inert electrodes such as platinum or graphite, the anode does not dissolve. Only active electrodes, such as copper in copper refining, dissolve. So this is not a common feature.

Answer: C.

Exam tip: When a question says "common feature" or "always," pick the definition-based answer. Here, the anode is always where oxidation occurs, while other statements, like the electrode dissolving, only hold in specific cases. Remember AN OX and RED CAT.