Question

When concentrated nitric acid is heated, it decomposes to give.
A.${O_2}$ and ${N_2}$
B.NO
C.${N_2}{O_5}$
D.$N{O_2}$ and ${O_2}$
E.Answer required

Answer 1

Hint: When we heat concentrated nitric acid $(HN{O_3})$ , it will decompose into nitrogen oxide $(N{O_2})$ , Oxygen $({O_2})$ and water $({H_2}O)$ .

Complete step by step answer:
When concentrated nitric acid $(HN{O_3})$ is heated, it decomposes to give nitrogen oxide gas $(N{O_2})$ , oxygen $({O_2})$ and water $({H_2}O)$ . This is a thermal decomposition. The solution formed is brownish yellow in colour. This reaction takes place slowly in the concentrated solution, at the room temperature initiated by the absorption of energy in the form of light.
 $4HN{O_3} \to 4N{O_2} + {O_2} + 2{H_2}O$
Nitrogen oxide $(N{O_2})$ is a pungent smelling reddish brown or yellowish-brown coloured gas.
So, when concentrated nitric acid is heated, it decomposes to give $N{O_2}$ and ${O_2}$ .

Therefore, the correct answer is option (D).

Note: Nitric acid $(HN{O_3})$ is a colourless fuming liquid which is used in the manufacture of inorganic and organic nitrates (as it is an oxidising acid) and nitro compounds for fertilizers, dye intermediates, explosives, and many different organic chemicals. It has a suffocating pungent odour. It may turn to appear as a pale yellow to reddish brown liquid generating red-brown fumes after settling. It is very toxic by inhalation and can cause severe burns and also corrosive to metals or tissue. Its molecular mass is 63.01 g/mol. There are many uses of nitric acid like it is used in the purification of gold as it dissolves impurities like copper, silver, zinc etc. It is used to prepare aqua regia as it helps to dissolve noble metals. This acid is not very stable.