A steel structure (Fe) is immersed in seawater that contains 0.010 M Mg²⁺ and 0.050 M Fe²⁺. The standard reduction potentials are: Mg²⁺ + 2e⁻ → Mg(s) E° = -2.37 V and Fe²⁺ + 2e⁻ → Fe(s) E° = -0.44 V. Using the Nernst equation, calculate the emf of the galvanic cell that would be set up between Mg and Fe under these conditions. Based on the sign of the emf, state whether Mg can be used as a sacrificial anode to protect the steel.

Question

A steel structure (Fe) is immersed in seawater that contains 0.010 M Mg²⁺ and 0.050 M Fe²⁺. The standard reduction potentials are: Mg²⁺ + 2e⁻ → Mg(s)   E° = -2.37 V and Fe²⁺ + 2e⁻ → Fe(s)   E° = -0.44 V. Using the Nernst equation, calculate the emf of the galvanic cell that would be set up between Mg and Fe under these conditions. Based on the sign of the emf, state whether Mg can be used as a sacrificial anode to protect the steel.

Accepted Answer

Ecell ≈ 1.95 V; Mg can be used as a sacrificial anode to protect the steel.

Waec Model Questions Vol1 2025 Chemistry Question 4

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