Chemistryhard · Past Paper
What is the oxidation number of Cr in $K_2Cr_2O_7$?
A+3
B+6
C+7
D+12
✓ Correct Answer: B — +6
2(+1) + 2(Cr) + 7(-2) = 0 => 2 + 2Cr - 14 = 0 => 2Cr = 12 => Cr = +6.
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