Empirical Formula

Definition

A formula that shows the simplest whole-number ratio of the atoms in a compound

Ex: H2ONot an Ex: H4O2

Percent to mass,Mass to mole,

Divide by small,Multiply 'til whole.

Poem for Steps

**If you have a 100g sample, the percent composition is the same as the mass

Example #1

Determine the empirical formula for a compound with the percent composition of 40.00% carbon, 6.72% hydrogen, and 53.28% oxygen.

Example #2

Determine the empirical formula for methyl acetate, which has the following chemical analysis: 48.64% carbon, 8.16% hydrogen and 43.20% oxygen.

Example #3

A 50.0 g sample of a compound contains 18.25 g Na, 19.05 g O, and 12.70 g S. Determine the empirical formula.

Example #4

A 50.0 g sample of a compound contains 2.52 g Be, 5.01 g Al, 15.68 g Si, and 26.97 g O. Determine the empirical formula.