# How many atoms are in 153 g of calcium?

Jun 7, 2017

$2.30 \times {10}^{24}$ $\text{atoms Ca}$

#### Explanation:

We're asked to calculate the number of atoms of $\text{Ca}$ in $153$ $\text{g Ca}$.

What we must first do is convert the given mass of calcium to moles of calcium, using its molar mass (referring to a periodic table, this is $40.08 \text{g"/"mol}$):

$153$ cancel("g Ca")((1"mol Ca")/(40.08cancel("g Ca"))) = color(blue)(3.82 color(blue)("mol Ca"

Using Avogadro's number, $6.022 \times {10}^{23} \text{particles"/"mol}$, we can calculate the number of atoms present:

color(blue)(3.82 cancel(color(blue)("mol Ca"))((6.022xx10^23"atoms Ca")/(1cancel("mol Ca")))

= color(red)(2.30 xx 10^24 color(red)("atoms Ca"