What is the formula weight?

Dec 13, 2016

Let's take a random formula, $C a C {O}_{3}$.
1 mole of calcium has a mass of $40.1 \cdot g$; 1 mole of carbon has a mass of $12.01 \cdot g$; 3 mole of oxygen has a mass of $3 \times 15.999 \cdot g$. Sum them together, and we get a so-called $\text{formula mass}$ of $100.12 \cdot g \cdot m o {l}^{-} 1$ (i.e. units are $g \cdot m o {l}^{-} 1$ or $g \cdot {\left(\text{Avogadro's Number}\right)}^{-} 1$ of reagent).