COMEDK · Chemistry · 18. Electrochemistry
Identify the correct statement regarding corrosion of iron rod left exposed to atmosphere.
- A The reaction occurring at the cathodic area is:
\(
\mathrm{O}_2(\mathrm{~g})+2 \mathrm{H}_2 \mathrm{O}(\mathrm{l})+4 \mathrm{e} \rightarrow 4 \mathrm{OH}^{-}\) - B The overall reaction occurring during the corrosion process is:
\(
2 \mathrm{Fe}_{(\mathrm{S})}+3 / 2 \mathrm{O}_2(\mathrm{~g})+6 \mathrm{H}^{+} \rightarrow 2 \mathrm{Fe}^{3+}+3 \mathrm{H}_2 \mathrm{O} ; \mathrm{E}^0=-1.23 \mathrm{~V}\) - C The reaction occurring at the cathodic area is:
\(
\mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e} \rightarrow 2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) ; \mathrm{E}^0=+1.23 \mathrm{~V}\) - D Reaction occurring at anodic area is:
\(
2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}+4 \mathrm{e}\)
Answer & Solution
Correct Answer
(C) The reaction occurring at the cathodic area is:
\(
\mathrm{O}_2(\mathrm{~g})+4 \mathrm{H}^{+}(\mathrm{aq})+4 \mathrm{e} \rightarrow 2 \mathrm{H}_2 \mathrm{O}(\mathrm{l}) ; \mathrm{E}^0=+1.23 \mathrm{~V}\)
Step-by-step Solution
Detailed explanation
At the anodic area: \(2Fe(s) \rightarrow 2Fe^{2+}(aq) + 4e^-\) (oxidation) At the cathodic area: \(O_2(g) + 4H^+(aq) + 4e^- \rightarrow 2H_2O(l)\); \(E° = +1.23\) V \(H^+\) ions come from dissolution of atmospheric \(CO_2\) in moisture forming weak carbonic acid. Option (3)…
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