The Application of an Activity Relating to the Determination of Avogadro’s Number in a Class of First-Year Science Students

Researchers have shown that students have difficulty understanding the concept of the mole and Avogadro’s number. The author’s opinion is that the reason for this is because they are not aware of the fact that the definitions of the mole and Avogadro’s number are based on carbon-12. In this manuscript, an activity based on the use of the mass spectrum of methane for the determination of Avogadro’s number and its application in a class of first-year students taking general chemistry is described. The activity consists of, first, determining the mass of a single carbon-12 atom in grams and then, using the definition of a mole, calculating Avogadro's number by dividing 12.00000 g mol–1 (carbon-12 mole weight) with this mass. The class was divided into seven groups and from the seven results from the groups, they obtained an average value of 6.0 x 1023 atoms 12C per mole of 12C for Avogadro’s number. In addition, from the average mass of a single carbon-12 atom in grams and the definition of the (unified) atomic mass unit (amu), they calculated the conversion factor that relates the amu to the gram as NA u = 1 g.