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JAMB Chemistry 1993 Question 23

Question 23

Electrolysis

Which of the following reactions occurs at the anode during the electrolysis of a very dilute aqueous solution of sodium chloride?

  1. A.OH− − e → OH
  2. B.Cl− − e− → Cl
  3. C.OH− + Cl− → HCl + O2−
  4. D.Na+ − e− → Na/Hg amalgam (over Hg)
Show the answer and explanation

Answer: A (OH− − e → OH)

Explanation

In very dilute NaCl, OH− ions are discharged at the anode in preference to Cl− because they are lower in the discharge series. Each OH− loses an electron, and oxygen is given off.