Atomic Structure and Properties

1.1 Moles and Molar Mass

Essential Knowledge:

*These are taken directly from College Board

◼ One cannot count particles directly while performing laboratory work. Thus, there must be a connection between the masses of substances reacting and the actual number of particles undergoing chemical changes. (SPQ-1.A.1)

◼ Avogadro’s number (NA = 6.022 x 1023 particles/mole) provides the connection between the number of moles in a pure sample of a substance and the number of constituent particles (or formula units) of that substance. (SPQ-1.A.2)   

◼ Expressing the mass of an individual atom or molecule in atomic mass units (amu) is useful because the average mass in amu of one particle (atom or molecule) or formula unit of a substance will always be numerically equal to the molar mass of that substance in grams. Thus, there is a quantitative connection between the mass of a substance and the number of particles that the substance contains. (SPQ-1.A.3)