Question

Define Mole

Answer 1

Hint:The mole (whose symbol is mol) is the unit of measurement for measuring the amount of a substance in the International System of Units (SI).
A mole can be defined as the amount of substance that contains the same number of chemical entities (atoms, ions, molecules, etc.) as there are in 12 g of Carbon-12 isotope, as defined by the General Conference on Weights and Measures.

Complete step by step answer:
Mole is a standard scientific unit used to measure large quantities of very small entities such as atoms, molecules, ions, etc.
12 g of carbon-12 isotope contains 6.022140857 ${\text{ X 1}}{{\text{0}}^{{\text{23}}}}$ carbon atoms.
1 mole of carbon = 12g of carbon.
For instance, 1 mole of oxygen = 16 g, 1 mole of sulphur = 32 g.
The number 6.022140857 ${\text{ X 1}}{{\text{0}}^{{\text{23}}}}$ is known as Avogadro’s number. Thus, we can define Avogadro’s number as the number of atoms present in 12 g of Carbon-12 isotope. It is represented as ${{\text{N}}_{\text{A}}}$.
Avogadro’s number is usually taken as 6.022 ${\text{ X 1}}{{\text{0}}^{{\text{23}}}}$ for simplification.
For the calculation of the number of moles present in the given amount of a substance, the given weight of that substance is divided by its molecular weight and the resultant answer is the number of moles present.
Till now we have defined moles in terms of weight or mass. Mole can also be defined in terms of volume.
At standard temperature and pressure conditions, one mole, i.e. 6.022140857 ${\text{ X 1}}{{\text{0}}^{{\text{23}}}}$ of any gas occupies 22.4 L of volume.


Note:The General Conference on Weights and Measures adopted a new definition of a mole on May 20, 2019. The new definition defines a mole as the Avogadro’s number, i.e. 6.022140857 ${\text{ X 1}}{{\text{0}}^{{\text{23}}}}$. Please note that the number of entities in a mole is the same form all the substances irrespective of their molecular weight or nature.