# How do you find formula mass of a compound?

Mar 24, 2018

Got a Periodic Table....?

#### Explanation:

Of course you have, you are doing your chemistry homework...

So let us find the formula mass of $C a S {O}_{4}$..

The Table tells us that the molar masses of calcium, sulfur, and oxygen, are $40.1 \cdot g \cdot m o {l}^{-} 1$, $32.06 \cdot g \cdot m o {l}^{-} 1$, and $16.0 \cdot g \cdot m o {l}^{-} 1$, respectively. The mole is simply a large number so chosen that $1 \cdot m o l$ of ""^1H ATOMS, has a mass of $1 \cdot g$ precisely... Of course, the elemental molar masses are listed on the Periodic Table; you are not required to remember then, tho you will soon commit the masses of the common atoms to memory..

And so we take the sum...

$\text{Formula mass of calcium sulfate} \equiv \left\{40.10 + 32.06 + 4 \times 16.00\right\} \cdot g \cdot m o {l}^{-} 1 = 136.16 \cdot g \cdot m o {l}^{-} 1$...