WAEC Chemistry 2011 Paper

Concept:One mole of any substance always contains the same fixed number of elementary entities.Explanation:This fixed number is called the Avogadro number or Avogadro's constant.Its value is $6.02 \times 10^{23}$ entities per mole.These entities may be atoms, molecules, ions, or particles.Hence, one mole of atoms contains exactly $6.02 \times 10^{23}$ atoms.This quantity is not the mass number, oxidation number, or atomic number of the substance.Therefore, the number of atoms in one mole equals the Avogadro number.Answer:D. Avogadro number