A sample of gold contains 7.02 x 1024 atoms. How many moles of gold are there?

Question

A sample of gold contains 7.02 x 1024 atoms. How many moles of gold are there?

a. 11.7 x 1023 moles

b. 7.02 moles

c. 6.022 x 1023 moles

d. 11.7 moles

Answer 1

First let's get a conversion factor for atoms to moles. Avogadro's number is 1 mole = 6.022 x 10^23 atoms.

The conversion factor then is 1 mole / 6.022 x 10^23 gold atoms. If we multiply this factor by the given number of gold atoms, we get

1 mole / 6.022 x 10^23 gold atoms x 7.02 x 10^24 gold atoms = 11.7 moles. Notice that the unit gold atoms cancels in the numerator and denominator leaving on mole as the unit. This tells you you have set up the problem correctly.