The decomposition of mercuric oxide (Hg)) on heating, resulting in the formation of mercury and oxygen is represented by the following chemical equation-
$2\mathrm{HgO}+180\mathrm{kJ}\to 2\mathrm{Hg}+{\mathrm{O}}_2$
Which one of the following represents the heat of formation of mercuric oxide?

The amount of heat absorbed or released during the formation of one mole of a compound from its component elements when each substance is in its normal physical state is known as the heat of formation, also known as the standard heat of formation, enthalpy of formation, or standard enthalpy of formation (gas, liquid, or solid).

The change in the enthalpy of a chemical reaction that takes place at constant pressure is known as the Heat of Reaction (also known as Enthalpy of Reaction). It is a thermodynamic unit of measurement that can be used to determine how much energy is released or created per mole during a reaction. Enthalpy is a state function since it is derived from state functions, such as pressure, volume, and internal energy.
When heated, mercury oxide releases both mercury and oxygen.
$2\mathrm{HgO}+180 \mathrm{kJ}\to 2\mathrm{Hg}+{\mathrm{O}}_2$
The following diagram illustrates how mercuric oxide forms at a high temperature:
$\mathrm{Hg}+\frac{1}{2}{\mathrm{O}}_2\to \mathrm{HgO}+90 \mathrm{kJ}$
Therefore, the enthalpy change required to produce one mole of HgO equals the heat of formation.

Hence, the correct answer is option B.