The red brown gas is released on heating lead nitrate due to:
A. Decomposition
B. Single displacement
C. Both A and B
D. Reduction

Hint: When lead nitrate is heated, it breaks down into lead monoxide, nitrogen dioxide, and oxygen. Now, we have to decide how we would classify this reaction.

Complete step by step answer:

Heating lead nitrate would produce lead monoxide, nitrogen dioxide, and oxygen as products -

$2Pb{ ({ NO }_{ 3 }) }_{ 2 }\quad \rightarrow\quad 2PbO+{ 4NO }_{ 2 }+{ O }_{ 2 }$

Here we can see that two gaseous products are formed. We all know oxygen is a colourless gas so the red brown gas would be nitrogen dioxide (${ NO }_{ 2 }$ ).

Decomposition reaction - Chemical decomposition is the process or effect of simplifying a single chemical entity into two or more fragments. Chemical decomposition is usually regarded and defined as the exact opposite of chemical synthesis.

Z $\rightarrow$ A + B
Single displacement reaction - Single displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and nonmetals take part in displacement reactions.

A-B + C $\rightarrow$ A + B-C

Reduction reaction - Reduction is the loss of oxygen atom from a molecule or the gaining of one or more electrons. A reduction reaction is seen from the point of view of the molecule being reduced, as when one molecule gets reduced another gets oxidised.

By looking at all above definitions of reactions, we can conclude that when we heat lead nitrate, it decomposes into PbO, ${ NO }_{ 2 }$ and ${ O }_{ 2 }$ and produces the red brown gas. Hence it is a Decomposition reaction.

So, the correct option is A.

Note: Nitrogen Dioxide (${ NO }_{ 2 }$) is one of a group of highly reactive gases known as oxides of nitrogen or nitrogen oxides (${ NO }_{ x }$). ${ NO }_{ 2 }$ is used as the indicator for the larger group of nitrogen oxides. ${ NO }_{ 2 }$ primarily gets in the air from the burning of fuel.