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How many moles of SnCl2 are needed to reduce 1 mole of K2Cr2O7 to Cr2O3 in acidic medium?

1. 3
2. 2
3. 1
4. 1/3

Correct answer: 3

Solution

K2Cr2O7 -> Cr2O3 gains 6 electrons (2 Cr x 3e). Each SnCl2 (Sn²+ -> Sn⁴+) loses 2 electrons, so 6/2 = 3 moles SnCl2.

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