Question #78d92

In this redox reaction, nitrogen gas is acting as the oxidizing agent and hydrogen gas is acting as the reducing agent.

#stackrel(color(blue)(0))("N")_ (2(g)) + 3 stackrel(color(blue)(0))("H")_ (2(g)) -> 2 stackrel(color(blue)(-3))("N") stackrel(color(blue)(+1))("H")_ (3(g))#

As you can see, the oxidation number of nitrogen is going from #color(blue)(0)# on the reactants' side to #color(blue)(-3)# on the products' side. This decrease in the oxidation number of nitrogen tells you that nitrogen is being reduced.

On the other hand, the oxidation number of hydrogen goes from #color(blue)(0)# on the reactants' side to #color(blue)(+1)# on the products' side. This increase in the oxidation number of hydrogen tells you that hydrogen is being oxidized.

You can thus conclude that nitrogen gas is being reduced to ammonia and hydrogen gas is being oxidized to ammonia.

Consequently, you can say that nitrogen gas acts as the oxidizing agent because it oxidizes hydrogen gas to ammonia while being reduced in the process.

Hydrogen gas acts as the reducing agent because it reduces nitrogen gas to ammonia while being oxidized in the process.