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WAEC Chemistry 2021 Paper

Question : 25

Total: 50

Consider the following diagram and use it to answer the question below

Which of the following cell notations represent the diagram

$\mathrm{B}^{2+} / \mathrm{B} // \mathrm{A} / \mathrm{A}^{3+}$
$\; \mathrm{A}^{3+} / \mathrm{A} // \mathrm{B} / \mathrm{B}^{2+}$
$\; \mathrm{B} / \mathrm{B}^{2+} // \mathrm{A} / \mathrm{A}^{3+}$
$\; \mathrm{A} / \mathrm{A}^{3+} // \mathrm{B}^{2+} / \mathrm{B}$

Validate

Solution:

Concept:

In a cell notation, the anode (oxidation) half-cell is written on the left and the cathode (reduction) half-cell on the right, separated by the salt bridge

//

Explanation:

From the diagram, electrode

\mathrm{A}

acts as the anode.

Oxidation occurs at

\mathrm{A}

\mathrm{A} \rightarrow \mathrm{A}^{3+} + 3e^-

Electrode

\mathrm{B}

acts as the cathode.

Reduction occurs at

\mathrm{B}

\mathrm{B}^{2+} + 2e^- \rightarrow \mathrm{B}

So the anode half-cell is written as

\mathrm{A}/\mathrm{A}^{3+}

, and the cathode half-cell is written as

\mathrm{B}^{2+}/\mathrm{B}

Joining them with the salt bridge gives:

\mathrm{A}/\mathrm{A}^{3+} // \mathrm{B}^{2+}/\mathrm{B}

Answer:

\mathrm{A}/\mathrm{A}^{3+} // \mathrm{B}^{2+}/\mathrm{B}

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