# How do you calculate the percentage of calcium in calcium carbonate, CaCO_3?

Nov 6, 2016

40.04 %

#### Explanation:

You take the atomic mass of calcium over the atomic mass of $C a C {O}_{3}$ and multiply it by 100 to get the percentage.

The mass of $C a$ is 40.078 g; the mass of $C$ is 12.01 g, and the mass of $3 O$
is 47.997 g ($\text{15.999 g} \times 3$).

Add all the masses together to get a total mass of 100.085 g.

So, ("40.078 g")/("100.085 g") = "0.4004 or 40.04 %".