# An engagement ring contains 3.97 * 10^-2 moles of gold. How many individual gold atoms are in this ring?

Jan 9, 2016

If you had 30 eggs would you be able to tell me how many dozen eggs you had? I think you would.

#### Explanation:

You have quoted a quantity of gold atoms in MOLES. Now it is a fact that if you have a MOLE of something (gold atoms, for instance, or even eggs) you have $6.02214$ $\times$ ${10}^{23}$ individual items of that substance. And you don't have to remember this number, because it will always be given to you in any test of chemistry or physics.

So the number of gold atoms:

$\text{Number of gold atoms}$ $=$ $3.97 \times {10}^{- 2} \cancel{m o l} \times 6.02214$ $\times$ ${10}^{23}$ $\cancel{m o {l}^{-} 1}$ $=$ ??

Please note the use of dimensions in this answer. I required a number, and got a dimensionless number. Capisce?