Consider the following redox reaction: 6FeSO4 + K2Cr2O7 + 7H2SO4 → 3Fe2(SO4)3 + Cr2(SO4)3 + K2SO4 + 7H2O. How many electrons are involved in the redox reaction?
Correct answer: B. 6
- A. 9
- B. 6
- C. 3
- D. 2
Explanation
In an acidic medium Cr is reduced from +6 to +3 as: Cr2O7-2+ 14H+ +6e- → 2Cr+3 + 7H2O and Fe2+ is oxidized to Fe3+ as: Fe2+→ Fe3++ e- So, 6 electrons are removed from Fe2+ (as there are 6 moles of Fe) and added to Cr6+ to make Cr3+ (2 moles of Cr, 3 electrons gained by each). So, the net transfer of electrons is 6. Hence, the number of electrons involved in the redox process is 6.
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