Question

How many atoms are in 90.8 g of carbon-12?

Answer 1

To find the number of atoms, we have to use Avogadro's number which says that there are 6.022 x 10 ^(23) atoms or molecules in 1 mol.

The first step is convert 90.8 grams of carbon-12 using its molar mass which is 12 g/mol:

$90.\text{8 g C}\cdot\frac{1\text{ mol C}}{12\text{ g C}}=7.567\text{ mol C.}$

Now, we have to convert this value to the number of atoms using Avogadro's number (6.022 x 10^(23) /mol):

$7.567\text{ mol C}\cdot\frac{6.022\cdot10^{23}atoms\text{ C}}{1\text{ mol C}}=4.56\cdot10^{24}atoms\text{ C.}$

The answer is that we have 4.56 x 10^(24) atoms in 90.8 grams of carbon-12.