What is the unit for measuring the amount of substance in chemistry?

The unit for measuring the amount of substance in chemistry is the mole. The mole is a fundamental concept in chemistry that quantifies the amount of a substance in terms of the number of entities, such as atoms, molecules, or ions. One mole is defined as containing approximately (6.022 \times 10^{23}) of these entities, a value known as Avogadro's number.

This measurement allows chemists to relate the mass of a substance to the number of particles it contains, facilitating calculations involving chemical reactions where the stoichiometry must be accurately represented. While grams and litres are units for measuring mass and volume respectively, they do not specifically represent the amount of substance in a way that accounts for the number of entities involved in chemical processes. Similarly, millilitres measure volume and are not directly related to the amount of substance. Thus, the mole is the appropriate and universally accepted unit in chemistry for quantifying the amount of substance.