What is the definition of a mole in chemistry?

The mole is a fundamental concept in chemistry that provides a bridge between the atomic scale and the macroscopic scale. Its definition, stating that one mole of any substance contains the same number of entities (such as atoms, molecules, or ions) as there are atoms in 12 grams of carbon-12, is crucial for understanding stoichiometry and chemical reactions.

This specific number is known as Avogadro's number, which is approximately (6.022 \times 10^{23}). This means that whether you have a mole of hydrogen atoms, a mole of water molecules, or a mole of sodium chloride, all contain about (6.022 \times 10^{23}) individual entities. This definition allows chemists to count particles by weighing them, making it easier to perform calculations in chemistry related to reactions and formulations.

The definitions provided in the other choices do not accurately capture the concept of a mole in the same way. For instance, defining a mole as a specific volume of liquid or as the weight of an element in grams overlooks the essential counting aspect of the mole. Additionally, relating the mole to mass divided by density does not adhere to the core definition that unifies the various forms of matter by the number of entities present