What are the oxidizing and reducing agent from these chemical reactions? And how many electrons did it gain (oxidizing) and lose (reducing)?

Question

a.) CuO + H₂ = Cu + H₂O

b.) Zn + Pb(NO₃)₂ = Pb + Zn(NO₃)₂

Answer 1

To find oxidizing and reducing agents, compare the oxidation numbers of the elements on each side of the equation. The one that gains electrons (was reduced) is the oxidizing agent. The one that loses electrons (was oxidized) is the reducing agent.

(a). CuO + H2 ==> Cu + H2O

Cu in CuO is 2+ and Cu on the right is zero. Cu gained electrons so CuO is the oxidizing agent.

H2 on the left is zero and on the right, it is 1+. H2 is therefore the reducing agent.

(b). Zn + Pb(NO3)2 ==> Pb + Zn(NO3)2

Zn on the left is zero and on the right it is 2+. Thus, Zn is the reducing agent.

Pb on the left is 2+ and on the right it is zero. Therefore, Pb is the oxidizing agent.