How many molecules are in 2.10 mol$C{{O}_{2}}$?

Hint: $C{{O}_{2}}$ is known by the name carbon dioxide. It is a colorless gas which has 53% higher density than air. Carbon dioxide molecules consist of carbon atoms covalently double bonded to oxygen atoms. It occurs in earth’s atmosphere naturally.

Complete step by step answer:
The mole is represented by the symbol mol. It is the unit of measurement for amounts in SI units where SI stands for International System units. A mole of substance or particles can be defined as containing exactly $6.02214076\times {{10}^{23}}$particles and the particles may be atoms, ions or electrons. In short 1 mol contains $6.02214076\times {{10}^{23}}$ of the specified particles and these $6.02214076\times {{10}^{23}}$is known as Avogadro’s constant.
Molecule is defined as the electrically neutral group of two or more atoms held together by chemical bonds. In the given example atoms of carbon and oxygen are held together with covalent bonds. Molecule can be homonuclear i.e. it consists of atoms of one chemical element and it can be heteronuclear which consists of more than one element. $C{{O}_{2}}$ is a heteronuclear molecule as it is composed of two elements known by the name carbon and oxygen.
We know that 1 mol of $C{{O}_{2}}$ contains $6.02214076\times {{10}^{23}}$ particles which can also be written as $6.023\times {{10}^{23}}$,
Then 2.10 mol of $C{{O}_{2}}$ contains $2.1\times 6.023\times {{10}^{23}}$i.e. $12.6843\times {{10}^{23}}$particles.
Thus, $12.6843\times {{10}^{23}}$ molecules are in 2.10 mol $C{{O}_{2}}$.

Note: Carbon dioxide is produced by all aerobic organisms when they metabolize organic compounds to produce energy even humans during respiration inhale oxygen and exhale carbon dioxide. It is also produced during the process of decay of organic materials.