Question

Which one reduces CuSO4
1) KCN. 2) KF. 3) NH3. 4) HNO3

Answer 1

In CuSO4, the oxidation number of Cu is +2, when reacting it can be changed to 0. That's why in such case CuSO4 is reducing, and it is an oxidizing agent. CuSO4 can be reduced by compound element in which changes its oxidation number from smaller to greater. For example, NH3 (N is oxidized, because its oxidation nunmber increases from -3 to 0).
Answer: NH3