Question

Define 1 mole.

Answer 1

1 mole is defined as the amount (mass) of a substance that contains the same number of elementary entities (atoms, molecules or ions) as there are atoms in 12.000 g of ${\mathrm{C}}^{12}$ isotope of carbon.

Avogadro's number (N_A) is a number of particles (atoms, molecules or ions) present in one mole of a substance.

N_A = 6.023 x 10²³