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Oxidation numbers of P in ` PO_4^(3-)`, of S in ` SO_4^(2-)`, and that of `Cr` in ` Cr_2O_7^(2-)` are respectively ,A. ` +3, +6` and `+6`B. ` +5, +6` and `+6`C. ` +3. +6`, and `+5`D. ` +5. +3`, and `+6` |
Answer» Correct Answer - B Let x be the oxidation number of P in ` PO_4^(3-)` ` x+4 (-2) =-3` ` x-8 =-3` or ` x= + 5` Let x be the oxidation number of S in ` SO_4^(2-)` : ` x +4 (-2) =-2` ` x-8 =-2` ` x = +6` Let x be the oxidation number of ` Ci` in ` Cr_2O_7^(2-) `: ` 2x+7 (-2) =-2` ` 2x -14 =-2` ` 2x = 12` ` x= +6 ` In all the three cases, we have used the rule that the sum of all oxidation numbers in a polyatomic ion must equal the charge on the ion. |
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