Question

What is true regarding the salt Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$)?

i. It contains both ionic and covalent bonds.

ii. It is soluble in water to form an alkaline solution.

iii. It completely decomposes into gaseous compounds on heating.

• A. (i) and (ii)
• B. (ii) and (iii)
• C. (i) and (iii)
• D. (i), (ii) and (iii)

Answer 1

The correct option is C

(i) and (iii)

Explanation of the correct option:

• Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$) contains both ionic and covalent bonds.
• The ionic bond is formed between Ammonium(${{\mathrm{NH}}_4}^{+}$) cation and Nitrate (${{\mathrm{NO}}_3}^{-}$) anion Nitrogen and Hydrogen atoms are joined by covalent bonds therefore this statement is true regarding Ammonium nitrate.
• Ammonium nitrate readily dissolves in water by dissociating into its constituent ions. This salt is acidic in nature as it is derived from a weak base(${\mathrm{NH}}_3$) and strong acid (${\mathrm{HNO}}_3$) so, it will not form an alkaline solution when dissolved in water so, it is an incorrect statement.
• Ammonium nitrate decomposes on heating and forms a gaseous compound Nitrous oxide(${\mathrm{N}}_2\mathrm{O}$) and water vapour hence, this statement is also correct.
• Reaction: $$\begin{gathered} {\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathrm{s}\right)\to {\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ (\mathrm{Ammonium}\mathrm{nitrate})(\mathrm{Nitrous}\mathrm{oxide})\left(\mathrm{Water}\right) \end{gathered}$$.
• Therefore, among the given statements, statements (i) and (iii) are true.

Explanation of the incorrect options:

• (A) When Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$) is dissolved in water, it gives an acidic solution because Ammonium nitrate is a salt of a strong acid and a weak base. So the $\mathrm{pH}$ of the solution will be less than 7 so statement (ii) is wrong, though it contains both ionic and covalent bonds. So, the combination in the given option is incorrect.
• (B) When Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$) is dissolved in water, it gives an acidic solution because Ammonium nitrate is a salt of a strong acid and a weak base. So the $\mathrm{pH}$ of the solution will be less than 7 so statement (ii) is wrong though Ammonium nitrate decomposes on heating and forms a gaseous compound Nitrous oxide(${\mathrm{N}}_2\mathrm{O}$) and water vapour. so the combination in the given option is incorrect.
• (C) A combination of all the three statements will be a wrong choice because statement (ii) is incorrect.

Hence, option (C) is correct. i.e., The statement (i) It contains both ionic and covalent bonds and (iii) It completely decomposes into gaseous compounds on heating, are true regarding the salt Ammonium nitrate(${\mathrm{NH}}_4{\mathrm{NO}}_3$).