Question

What is the empirical formula for the compound containing 13.5 g Ca, 10.8 g O, and 0.675 g H?

Answer 1

`Ca(OH)_2`

Explanation:

We divide each given mass by the atomic mass of each individual element:

`"Calcium:"` `(13.5*g)/(40.1*g*mol^-1)=0.337*mol.`

`"Oxygen:"` `(10.8*g)/(15.999*g*mol^-1)=0.675*mol.`

`"Hydrogen:"` `(0.675*g)/(1.008*g*mol^-1)=0.675*mol.`

If we divide thru by the smallest atomic quantity, we get an empirical formula of, `CaH_2O_2`, i.e. `Ca(OH)_2`.