# Question 19e39

Oct 22, 2017

$= 1.202 \cdot {10}^{24} C a$ Atoms

#### Explanation:

We are doing a grams to moles to atoms conversion.

You will need Avogadro's Constant and the amount of grams per mole of Calcium from whichever periodic table you happen to have.

I used Ptable.

$80.0 g C a \cdot \frac{1 m o l C a}{40.078 g C a} \cdot \frac{6.022 \cdot {10}^{23} C a}{1 m o l C a}$ Atoms

You can always double check to make the proper units are left in numerator of the last conversion factor.

$= 1.202 \cdot {10}^{24} C a$ Atoms

For proper significant figures, if you were given the value (80g) for Calcium, there is only one significant figure in that number.
$= {10}^{24} C a$ Atoms