An aqueous solution of copper(II) sulfate (CuSO_4) undergoes electrolysis using copper she… — JAMB UTME

An aqueous solution of copper(II) sulfate ( $CuSO_4$ ) undergoes electrolysis using copper sheets as both the anode and cathode. Which statement correctly describes the reaction occurring at the anode and identifies the primary factor governing this process?

The copper anode dissolves into solution as $Cu^{2+}$ ions, governed by the nature of the electrode material.Answer
B
Hydroxide ions ( $OH^-$ ) are discharged to liberate oxygen gas, governed strictly by their higher position in the electrochemical series relative to sulfate ions ( $SO_4^{2-}$ ).
C
Sulfate ions ( $SO_4^{2-}$ ) are preferentially discharged to produce sulfur dioxide gas, governed by the high concentration of sulfate ions relative to hydroxide ions ( $OH^-$ ).
D
Hydrogen ions ( $H^+$ ) are discharged to liberate hydrogen gas, governed by the low electrode potential of water molecules.

Answer

The copper anode dissolves into solution as

Cu^{2+}

ions, governed by the nature of the electrode material.

In the electrolysis of copper(II) sulfate solution using active copper electrodes, oxidation occurs at the anode. Because copper is an active metal electrode, dissolving copper metal into copper(II) ions (

Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-

) requires less energy than discharging hydroxide ions or sulfate ions. Thus, the nature of the electrode material is the governing factor.

Step-by-Step Solution

Identify the ions present in aqueous

CuSO_4

solution.

Cations:

Cu^{2+}

and

H^+

. Anions:

SO_4^{2-}

and

OH^-

Electrolysis of aqueous solutions involves ions from both the dissolved salt and water dissociation.

Analyze the nature of the electrode at the anode.

The anode is made of copper, which is an active (reactive) electrode, not an inert electrode like platinum or graphite.

Active electrodes participate directly in the electrochemical reaction.

Determine the preferred anodic oxidation reaction.

Copper atoms from the anode oxidize preferentially (

Cu(s) \rightarrow Cu^{2+}(aq) + 2e^-

) instead of discharging

OH^-

SO_4^{2-}

anions.

The energy required to oxidize metallic copper atoms is lower than that needed to discharge anions from the solution, demonstrating that the nature of the electrode overrides electrochemical series position and ion concentration.

Key Concept

Influence of the Nature of Electrodes on Preferential Discharge

Estimated Time:2m 0s

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Answer

Step-by-Step Solution

Key Concept

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