Half cell reaction standard reduction potential, Eo=Fe2+ 2e- → Fe -0.41Cu2+ 2e- → Cu 0.34Ni2+ 2e- → Ni -0.25Zn2+ 2e- → Zn -0.76Referring to the table above which metal could be used to prevent iron from corrosion?
Correct answer: B. Zn only
- A. Cu only
- B. Zn only
- C. Cu & Ni only
- D. Ni and Zn only
Explanation
The correct answer is Zn only. Zinc has a standard reduction potential of -0.76 V, which is more negative than iron's -0.41 V. This makes zinc an effective sacrificial anode, as it will oxidize before iron, thus protecting it from corrosion. Copper and nickel have higher (less negative) reduction potentials than iron, making them unsuitable for this purpose. Therefore, only zinc can provide the necessary protection.
This question appeared on the ETEA MDCAT 2013 paper, which you can sit online with every answer explained.
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About Redox Reactions
Redox reactions involve oxidation and reduction occurring together, with electrons transferred between species or oxidation numbers changing. The topic covers assigning oxidation states, identifying oxidizing and reducing agents, balancing redox equations by oxidation number or half-reaction methods, and connecting chemical changes with galvanic and electrolytic cells.
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