Question

Which one of the following nitrate will decompose to give NO₂ on heating ?

• A. NaNO₃
• B. KNO₃
• C. RbNO₃
• D. LiNO₃

Answer 1

The Correct Option is D

Lithium nitrate (LiNO₃) decomposes upon heating to form lithium oxide (Li₂O), nitrogen dioxide (NO₂), and oxygen (O₂):

• \(\text{LiNO₃} \xrightarrow{\text{heat}} \text{Li₂O} + 2 \, \text{NO₂} + \text{O₂}\)

In contrast, other alkali metal nitrates like NaNO₃, KNO₃, and RbNO₃ decompose to give alkali metal nitrites (e.g., NaNO₂, KNO₂, RbNO₂) and oxygen, but not NO₂ directly.

Thus, LiNO₃ is the only nitrate among the options that decomposes to release NO₂ on heating, making (D) the correct answer.

Answer 2

Among the alkaline earth metal nitrates, lithium nitrate (LiNO₃) decomposes on heating to form NO₂ and O₂, producing a characteristic brown gas (NO₂). Other nitrates like NaNO₃ and KNO₃ usually decompose to form the respective oxides.