How do you calculate empirical formula from percentage composition?

To calculate the empirical formula from percentage composition, convert the percentages to grams and then to moles.

The empirical formula of a compound represents the simplest whole-number ratio of the atoms or ions in the compound. To calculate this from the percentage composition, you first need to convert the percentages into grams. This is done by assuming you have 100g of the substance, so the percentage is the same as the mass in grams.

For example, if a compound is 40% carbon, 6.7% hydrogen, and 53.3% oxygen, you would have 40g of carbon, 6.7g of hydrogen, and 53.3g of oxygen.

Next, you need to convert these masses into moles. This is done by dividing the mass of each element by its atomic mass. The atomic mass can be found on the periodic table. For example, the atomic mass of carbon is approximately 12, hydrogen is approximately 1, and oxygen is approximately 16.

So, for the example above, you would have approximately 3.33 moles of carbon (40 ÷ 12), 6.7 moles of hydrogen (6.7 ÷ 1), and 3.33 moles of oxygen (53.3 ÷ 16).

The final step is to divide each of these mole values by the smallest value to get the simplest whole-number ratio. In this case, the smallest value is 3.33, so you would divide each value by this to get the ratio. This gives you a ratio of 1:2:1, so the empirical formula of the compound is CH2O.

Remember, the empirical formula does not necessarily represent the actual number of atoms in a molecule of the compound, just the simplest ratio. The molecular formula may be a multiple of the empirical formula.