How many O atoms of mass 15.99 amu are in 15.99 g of oxygen?

An atomic mass unit (amu) is a standard unit of mass that quantifies mass on an atomic or molecular scale. It is defined as one twelfth of the mass of a carbon-12 atom, approximately 1.66 x 10^-27 kg. In the context of the question, the mass of oxygen is given as 15.99 amu, which indicates the mass of a single oxygen atom.

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For oxygen, the molar mass is approximately 16 g/mol, which means that one mole of oxygen atoms weighs about 16 grams. This concept is crucial for converting between grams and moles, allowing us to determine the number of atoms in a given mass of a substance.

Avogadro's number, approximately 6.022 x 10^23, is the number of atoms, ions, or molecules in one mole of a substance. This constant allows chemists to relate macroscopic quantities of material to the number of individual particles. In this question, it is used to calculate how many oxygen atoms are present in 15.99 grams of oxygen by first determining the number of moles and then multiplying by Avogadro's number.