Question

How many atoms are there in a 20 g sample of gold?

Answer 1

We know that there are 20g of gold and we must calculate how many atoms there are in the sample.

First, we must use the molecular mass of the gold,

`M(Au)=196.97(g)/(mol)`

Then, we must use the next formula

`n(Au)=(m(Au))/(M(Au))`

Where,

- n represents the number of molecules

- m is the given mass (20 g)

- M is the molecular mass

Now, replacing the values in the formula

`n(Au)=(20g)/(196.97(g)/(mol))=0.1015\text{mol}`

Finally, we must use that there are 6.022 * 10^23 molecules per mole

`N(Au)=n(Au)\cdot N_a=0.1015mol\cdot6.022\cdot10^(23)=6.1\cdot10^(22)`

ANSWER:

6.1 * 10^22 atoms are in 20g sample of gold.