# What is a formula mass example?

Jul 29, 2017

$\text{Sodium carbonate}$ has a formula mass of $105.99 \cdot g \cdot m o {l}^{-} 1$. How do we arrive at this figure?

#### Explanation:

Well we take the weighted sum of the atomic masses involved in the formula, $N {a}_{2} C {O}_{3}$, and that is..........

$\left\{2 \times 22.99 \left(N a\right) + 12.011 \left(C\right) + 3 \times 16.00 \left(O\right)\right\} \cdot g \cdot m o {l}^{-} 1$

$= 105.99 \cdot g \cdot m o {l}^{-} 1$.

From where did I get the individual atomic masses? Did I just know them off the top of my head?

Is this what you want? You may want to clarify......