Question

In an experiment, a 2.514 g sample of calcium is heated in oxygen and the compound formed has a mass of 3.518 g. What is the empirical formula for the compound?

Answer 1

We get an empirical formula of `CaO`.

Explanation:

We can work out the individual masses of the elements in the binary compound, and we convert this to a molar quantity of each element:

`"Moles of calcium"` `=` `(2.514*g)/(40.1*g*mol^-1)=0.0627*mol`

`"Moles of oxygen"` `=` `(3.518*g-2.514*g)/(16.00*g*mol^-1)=0.0627*mol`

We divide thru by the smallest molar quantity, and since there are equimolar quantities of metal and oxygen, the empirical formula is:

`CaO`.