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In galvanizing, why does the zinc layer corrode before the iron beneath it?
AZinc is less electropositive than iron
BZinc is more electropositive than iron
CZinc is denser than the iron below
DZinc is a much softer metal than iron
Answer & Solution
Correct answer: B. Zinc is more electropositive than iron
1. Galvanizing coats iron with a thin zinc layer.
2. Zinc is more electropositive (more reactive) than iron.
3. Being more reactive, the zinc corrodes first, sparing the iron.
4. Only after the zinc wears away does the exposed iron begin to rust, so the 'less electropositive' option is wrong.
5. Density and softness are not the reason zinc corrodes first.
6. Hence the correct reason is that zinc is more electropositive than iron.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 8 "Metallurgy", p.116_
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