Paper 3 · redox chemistry
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 is +5, in (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
