Question

Identify the reducing agent in the following reaction?
$2N{{O}_{2}}(g)+7{{H}_{2}}(g)\to 2N{{H}_{3}}(g)+4{{H}_{2}}O(g)$

Answer 1

In a redox chemical process, a reducing agent is an element or molecule that loses or "donates" an electron to an electron receiver. The oxidation state of the reducer grows while the oxidation state of the oxidizer drops; this is represented as reducers "undergo oxidation" and "are oxidised," whereas oxidizers "undergo reduction" and "are reduced." Consequently, reducing agents "reduce" oxidizers by lowering their oxidation state, whereas oxidising agents "oxidise" reducers by raising their oxidation state.

Complete answer:
Assuming you're dealing with a redox reaction, begin by assigning oxidation numbers to the components involved in the process.
$2{{\overset{+4-2}{\mathop{~\text{NO}}}\,}_{2(~\text{g}]}}+7{{\overset{0}{\mathop{\text{H}}}\,}_{2(~\text{g}]}}\to 2~\overset{-3}{\mathop{\text{N}}}\,{{\overset{+1}{\mathop{{{\text{H}}_{3}}}}\,}_{(~\text{g}]}}+4{{\overset{+1}{\mathop{\text{H}}}\,}_{2}}{{\overset{-2}{\mathop{\text{O}}}\,}_{2(~\text{g}]}}$
An element must be oxidised by losing electrons and reduced by gaining electrons in order for a redox reaction to take place.
The oxidation number of an element increases when electrons are lost. The oxidation number of an element falls as it accumulates electrons. As a result, seek for items that correspond to that description. Notice how the oxidation state of nitrogen changes from +4 on the reactants' side when it's coupled with oxygen in nitrogen dioxide, $N{{O}_{2}}$ , to - 3 on the products' side when it's partnered with hydrogen in ammonia, $N{{H}_{3}}$ .
The oxidation number of nitrogen has decreased, therefore it has been lowered. When hydrogen is coupled with nitrogen in ammonia, its oxidation number changes from 0 on the reactants' side when it forms a hydrogen molecule to 1 on the products' side. You may say that hydrogen has been oxidised since its oxidation number has risen. As a result, a redox reaction occurred. A reducing agent is essentially a compound that comprises one element that gives electrons, decreasing another element by doing so. An oxidising agent, on the other hand, is a compound that comprises an electron-accepting element that oxidises another element by stealing its electrons.
So, in your instance, you know that hydrogen is being oxidised, which implies it is giving electrons in this process. Because it lowers nitrogen, this indicates that it is working as a reducing agent. Nitrogen, on the other hand, is being reduced, which means it is absorbing electrons. Because it oxidises hydrogen, this indicates that it is functioning as an oxidising agent.
As a result, the reducing agent is hydrogen gas, and the oxidising agent is nitrogen dioxide.

Note:
Corrosion is defined as the "degradation of metals as a result of electrochemical action" and is caused by reducing and oxidising substances. Corrosion needs the presence of an anode and a cathode. Because the anode is a reducing agent that loses electrons, oxidation always happens in the anode, and the cathode is an oxidising agent that gets electrons, reduction always occurs in the cathode. When there is a difference in oxidation potential, corrosion develops. Given an electrical connection and the presence of an electrolyte, the anode metal begins to deteriorate when this occurs.