Question

What is the empirical formula for a compound that is 33.36% calcium, 26.69% sulfur, and 40.00% oxygen?

Answer 1

The empirical formula is `CaSO_"3"`.

Explanation:

1: We have to do is assume 100g.

Therefore:
- Calcium: `33.36% -> 33.36g`
- Sulfur: `26.69% -> 26.69g`
- Oxygen: `40.00% -> 40.00g`

We do this because the percent is in relation to 100%. By assuming 100%, all the values can be viewed as values in grams.

2: We find the mols of each element.

Now that we have the mass, the molar mass is the individual molar mass of each element.

`n_"C" = m/M`

`=33.36/40.08`

`=0.832335329`

`n_"S" = m/M`

`=26.69/32.07`

`=0.83224197`

`n_"O" = m/M`

`=40.00/16.00`

`=2.5`

3: Now we take the lowest value of mols and divide every other mol by that.

Calcium has the smallest mol: `0.832335329`

Calcium:

`=0.832335329/0.832335329`

`=1`

Sulfur:

`=0.83224197/0.832335329`

`=1`

Oxygen:

`=2.5/0.832335329`

`=3`

Therefore, the empirical formula is `CaSO_"3"`.