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

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Answer 1 · 2017-02-02T03:01:22

The empirical formula is #CaSO_"3"#.

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"#.