Question

How many atoms are in a sample of 68.7 grams copper (Cu)?

Answer 1

First find the moles of the substance: Moles = mass / RFM 

moles = 68.7 / 

Answer 2

To find the number of atoms in the sample of copper, we need its atomic mass and the use of the Avogadro's number to find the equivalent units in terms of atoms.

68.7 g Cu ( 1 mol / 63.55 g ) ( 6.022 x 10^23 atoms / 1 mol ) = 6.51 x 10^23 atoms Cu