What changes in oxidation numbers take place when copper reacts with concentrated nitric acid to give a blue solution and a brown acidic gas?

ACopper: +1, Nitrogen: +1

BCopper: +2, Nitrogen: +1

CCopper: +2, Nitrogen: +2

DCopper: +1, Nitrogen: +2

Explanation

The marking scheme gives answer B. Cu goes from 0 to +2 (change of +2). N in

HNO_3

is +5, in

NO_2

(brown gas) is +4, so change is -1 (magnitude 1). Answer B: Cu changes by 2, N changes by 1.

ZIMSEC Chemistry Paper 3, June 2009, Q7

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