# What is the total number of moles present in a 52.0 gram sample of NaN_3?

## Gram-formula mass = 65.0 grams/mole

Nov 15, 2016

$\text{0.800 moles}$

#### Explanation:

The formula for calculating moles given the mass and a compound is:

$n = \frac{m}{M}$

$n$ = moles
$m$ = mass in grams $\left(\text{g}\right)$
$M$ = molar mass $\left(\text{g/mol}\right)$

The molar mass is the sum of all the atomic masses in the compound.

$\text{Na" = "22.99 g/mol}$
$\text{N" = "14.01 g/mol} \times 3 \to$ (there are $3$ $\text{N}$ atoms)

Add them up and you get $\text{65.02 g/mol}$

$n = \frac{m}{M}$

 = (52.0 cancel("g"))/(65.02 cancel("g")/"mol")

$= \text{0.799753921 moles}$

$= \text{0.800 moles } \to$ (rounded to three sig figs)

Therefore, there are $0.800$ moles in 52.0g of ${\text{NaN}}_{3}$.

I hope this made sense :)