Question 4.17: The reaction of oxygen with hydrazine is used to remove diss...
The reaction of oxygen with hydrazine is used to remove dissolved oxygen gas from aqueous solutions:
O_{2}(aq) + N_{2}H_{4}(aq) → 2 H_{2}O(\ell) + N_{2}(g)
and the combustion of hydrazine produces enough energy that the substance is used as a rocket fuel. Identify the species oxidized, the species reduced, the oxidizing agent, and the reducing agent in the balanced chemical equation.
Collect and Organize The reactants are the element oxygen and the compound hydrazine. The products are water and nitrogen.
Analyze The O.N. of the oxygen atoms in O_{2} changes from zero to -2 in H_{2}O. The O.N. of nitrogen changes from -2 in N_{2}H_{4} to zero in N_{2}. The O.N. = +1 of hydrogen is unchanged.
Solve
We see that oxygen is the oxidizing agent because the oxidation number of nitrogen increases. This means that O_{2} is reduced and N_{2}H_{4} is the reducing agent.
Think About It We tend to identify the specific atoms that are oxidized or reduced, whereas whole molecules or ions are identified as the oxidizing agents or reducing agents. In the equation in this exercise, nitrogen is oxidized but N_{2}H_{4} is the reducing agent.