How can you determine the empirical formula from percent composition?

You can determine the empirical formula from percent composition by converting the percentages into grams and then moles.

To determine the empirical formula from percent composition, you first need to assume that you have a 100g sample of the compound. This is because the percent composition is based on the mass percent of each element in a compound. For example, if a compound is 40% carbon, 6% hydrogen, and 54% oxygen, you would assume that you have 40g of carbon, 6g of hydrogen, and 54g 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 12.01g/mol, hydrogen is approximately 1.01g/mol, and oxygen is approximately 16.00g/mol. So, you would have approximately 3.33 moles of carbon, 5.94 moles of hydrogen, and 3.38 moles of oxygen.

Once you have the number of moles for each element, you then need to divide each of these values by the smallest number of moles calculated. This is to ensure that the ratio of elements in the empirical formula is in the simplest whole number ratio. In this example, the smallest number of moles is 3.33, so you would divide each of the mole values by 3.33. This would give you a ratio of 1:1:1 for carbon, hydrogen, and oxygen respectively.

Therefore, the empirical formula for this compound would be CHO. This is the simplest, most reduced ratio of elements in a compound. It's important to note that the empirical formula does not provide information about the actual number of atoms in a molecule of the compound, just the simplest whole number ratio of the atoms. The molecular formula may be a multiple of the empirical formula.