Question

Nitrogen is liberated by the thermal decomposition of only-
(A)$N{H_4}N{O_2}$
(B)$Na{N_3}$
(C)${(N{H_4})_2}C{r_2}{O_7}$
(D)All of these

Answer 1

Decomposition is a type of chemical reaction in which a compound breaks into its simpler parts under suitable conditions. It is the reverse of the Combination reactions. Thermal decomposition is the process of breaking of the compound in the presence of heat. Decomposition temperature is the one at which the substance decomposes.

Complete answer:
Nitrogen$({N_2})$ gas is a colorless, tasteless and odourless gas which is highly abundant (78%) in the atmosphere. Nitrogen is of great importance in production of proteins that form important part of living body as well as in the production of fertilizers, dyes, nylons, explosives, nitric acid etc.
The thermal decompositions of Azides, dichromates and Nitrites produces Nitrogen. In the question we are some chemical compounds and asked if they produce Nitrogen on thermal decomposition, so let us look at the options one by one-
(A) $N{H_4}N{O_2}$ is Ammonium Nitrite. The thermal decomposition occurs as follows-
$N{H_4}N{O_2}\xrightarrow{\Delta }{N_2} + 2{H_2}O$
The reaction produces Nitrogen gas and water vapour.
(B) $Na{N_3}$ is sodium azide. The thermal decomposition occurs as follows-
$2Na{N_3}\xrightarrow{\Delta }2Na + 3{N_2}$
The reaction produces Sodium metal and Nitrogen gas. Very pure nitrogen is obtained by this method.
(C) ${(N{H_4})_2}C{r_2}{O_7}$ is Ammonium dichromate. These are red coloured crystals. The thermal decomposition occurs as follows-
${(N{H_4})_2}C{r_2}{O_7}\xrightarrow{\Delta }C{r_2}{O_3} + {N_2} + 4{H_2}O$
Ammonium dichromate is thermodynamically unstable and hence it decomposes into dark green chromium (III) oxide and Nitrogen gas. The reaction occurs with flashes of light.
Thus all of them are possible options hence the correct answer is Option (D).

Note:
Apart from all of these reactions Nitrogen is produced by several other methods like Oxidation of Ammonia by Bromine water or oxidation of Ammonia with hot cupric oxide ,Fractional distillation of liquefied air, Reaction of Bleaching powder with Ammonia, Reaction of silver oxide and Ammonia, Reaction of Ammonium chloride and Sodium nitrite etc.