Avogadro's Number Example Chemistry Problem

Question: Calculate the mass in grams of a single carbon (C) atom.

Solution

To calculate the mass of a single atom, first look up the atomic mass for carbon from the Periodic Table.
This number, 12.01, is the mass in grams of one mole of carbon. One mole of carbon is 6.022 x 10²³ atoms of carbon (Avogadro's number). This relation is then used to 'convert' a carbon atom to grams by the ratio:

mass of 1 atom / 1 atom = mass of a mole of atoms / 6.022 x 10²³ atoms

Solve for mass of 1 atom

mass of 1 atom = mass of a mole of atoms / 6.022 x 10²³

mass of 1 C atom = 12.01 g / 6.022 x 10²³ C atoms
mass of 1 C atom = 1.994 x 10^-23 g

Answer

The mass of a single carbon atom is 1.994 x 10^-23 g .