When electricity is passed through brine, three useful products are formed. Name the products and state at which electrode each gas is released.
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
When electricity is passed through brine (concentrated NaCl solution), three useful products are formed:
- Chlorine gas – released at the anode (positive electrode)
- Hydrogen gas – released at the cathode (negative electrode)
- Sodium hydroxide (NaOH) – formed in the solution near the cathode
This process is called the chlor-alkali process. The overall reaction is:
$$2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)$$
Source: Chapter 1 (Chemical Reactions and Equations), electrolysis/chlor-alkali process
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Explanation
- The examiner expects all three products named (1 mark each): chlorine, hydrogen, and sodium hydroxide.
- For full marks, state which gas is at which electrode — Cl₂ at anode, H₂ at cathode.
- NaOH is not a gas; it remains in solution, so don't say it is released at an electrode.
- The equation is a bonus but good to include for clarity.