Question

In which of the following nitrate can be converted into metal oxide in heating?
(A) $Li$
(B) $Na$
(C) Both A and B
(D) None of these

Answer 1

Hint:As we know that metals nitrates generally decompose on heating to give metal oxides, oxygen as well as nitrogen dioxide having brown fumes. But alkali metals nitrates behave differently upon heating, releasing colourless and odourless gas due to their size difference.

Complete step-by-step solution:As we know that metal nitrates on heating generally results in the formation of metal oxides, oxygen and brown fumed nitrogen oxide. But due to differences in the size and other chemical properties, not all members of the group behave the same.
In the given question, Lithium possesses some anomalous properties which are very different from other members of the group due to its small size and greater polarising power. So when lithium nitrate is heated, it results into lithium oxide and we can show this reaction through following equation:
$4LiN{O_3} \to 2Li{O_2} + 4N{O_2} + {O_2}$
Talking about other members of the group, they do not form corresponding metal oxides on heating their metal nitrate compounds. Rather, they give respective nitrites. For instance: sodium nitrate when heated, it decomposes to form the corresponding nitrite and give an oxygen molecule which we can show through the following equation:
$2NaN{O_3} \to 2NaN{O_2} + {O_2}$

Therefore, from the above explanation we can say that the correct answer is (A) where lithium is the only one which is converted to metal oxide after heating its nitrate.

Note:Remember that magnesium nitrate when heated, it decomposes to give magnesium oxide and nitrogen dioxide and liberates half oxygen. When sodium nitrate is heated it forms nitrogen oxides which can cause fire hazards as it decomposes explosively and is a strong oxidising agent.