Question

The below reaction is an example of
$4N{H_3}(g) + 5{O_2}(g) \to 4NO(g) + 6{H_2}O(g)$
(i). Displacement reaction
(ii). Combination reaction
(iii). Redox reaction
(iv). Neutralization reaction.
A. (i) and (iv)
B. (ii) and (iii)
C. (i) and (iii)
D. (iii) and (iv)

Answer 1

The given reaction between ammonia and oxygen can be categorized in more than one category depending on the number of products formed and the kind of changes that take place. We have to observe the change in the oxidation state, the basic or acidic properties and if any cation or anion is being exchanged.

Complete answer:
The balanced chemical equation for the reaction between ammonia and oxygen that produces nitrogen monoxide and water can be written as follows:
$4N{H_3}(g) + 5{O_2}(g) \to 4NO(g) + 6{H_2}O(g)$
Even though ammonia is basic in nature it is reacting with oxygen which does not show any acidic or basic property. Therefore this reaction cannot be categorized as a neutralization reaction.
The hydrogens attached to the nitrogen atom in ammonia get replaced by the oxygen atoms. Even though this reaction does not contain an exchange of ions yet it can be classified as a displacement reaction in which oxygen displaces hydrogen atoms. Covalent compounds can also show displacement reaction.
The removal of hydrogen atoms and new bonds formed with oxygen atoms is defined as an oxidation process. Nitrogen in ammonia gets rid of hydrogens and forms bonds with oxygen and therefore gets oxidized in the reaction. Oxygen itself gets attached to hydrogen atoms and is said to be reduced. This simultaneous process of oxidation and reduction can be called a redox reaction.

Hence, the given reaction is a Displacement reaction as well as Redox reaction. So, option (C) is correct.

Note:
The oxidation and reduction reactions can be identified by observing the exchange of oxygen atoms or by calculating the change in oxidation states of elements. Oxygen in its molecular form has zero oxidation state and changes to $- 2$ in water.