Four metal–ion couples are investigated under standard conditions

CHEMISTRY · Multi-part · A Level · Chemistry · Electrode potentials · Electrode potentials

Problem

Four metal–ion couples are investigated under standard conditions. Their standard electrode potentials are given below. Half-Reaction E∘E^\circ (V) A2+(aq)+2e−→A(s)A^{2+}(aq) + 2e^{-} \to A(s) +0.11 B+(aq)+e−→B(s)B^{+}(aq) + e^{-} \to B(s) -0.25 C3+(aq)+3e−→C(s)C^{3+}(aq) + 3e^{-} \to C(s) +0.52 D2+(aq)+2e−→D(s)D^{2+}(aq) + 2e^{-} \to D(s) -0.40 Assume that any two of these electrodes can be combined to construct a galvanic cell operating under standard conditions. (a) For each of the six possible unordered pairs of half-reactions (A with B, A with C, etc.), calculate the corresponding standard cell potential, Ecell∘E^\circ_{\text{cell}}. Clearly show how you arrive at each numerical value. (b) Identify the electrode pair that produces the largest positive Ecell∘E^\circ_{\text{cell}}. Write the balanced overall redox equation for that pair, including physical states. (c) For the selected pair in part (b), specify which substance is oxidized and which is reduced. Explain how the direction of electron flow in the external circuit is consistent with your identification.

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