A) to count large numbers of very small particles, such as atoms or molecules.
B) to relate the mass and the number of particles of a substance to each other.
C) to relate the mass and the volume of a substance to each other.
D) all of these are true.
Avogadro's number is defined as the number of elementary particles (molecules, atoms, compounds, etc.) per mole of a substance. It is equal to 6.022×1023 mol-1 and is expressed as the symbol NA. Avogadro's number is a similar concept to that of a dozen or a gross.
