WAEC 2015 Chemistry · Question 42

Which of the following metals is the strongest reducing agent?

Options

A.Sodium
B.Silver
C.Potassium
D.Copper

Answer: C. Potassium

Explanation written with AI and checked against the answer key

Step 1: Analyze the question A reducing agent donates electrons, so it gets oxidized. The metal that loses electrons most easily is the strongest reducing agent. Step 2: The concept In the electrochemical (reactivity) series, the more reactive a metal, the more readily it loses electrons, and the stronger its reducing power. The series from most to least reactive is: K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au A very negative standard electrode potential (E°) means the metal is easily oxidized, so it is a strong reducing agent. Step 3: Compare the options | Metal | E° (V) | Reducing strength | |---|---|---| | Potassium (K⁺/K) | −2.93 | Strongest | | Sodium (Na⁺/Na) | −2.71 | Very strong | | Copper (Cu²⁺/Cu) | +0.34 | Weak | | Silver (Ag⁺/Ag) | +0.80 | Weakest | Potassium has the most negative electrode potential, and it sits at the top of the reactivity series among these options. Its single outer electron is lost very easily because its atom is larger and the outer electron is farther from the nucleus than in sodium. Step 4: Answer Potassium is the strongest reducing agent, so the answer is C. Exam tip: Remember "Reactive metal = strong reducing agent." Metals at the top of the reactivity series (K, Na, Ca) lose electrons easily. Metals at the bottom (Cu, Ag, Au) are good oxidizing agents in their ion form instead. If you see the same question with Lithium, note that Li has the most negative E° (−3.04 V), but Potassium is usually the answer in WASSCE because of its position in the reactivity series.

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