Determining Percent Composition of a Compound

A compound was known to contain C, H, & O. Complete combustion of 20.00 g of this compound produced 44.04 g CO2 and 14.32 g of H2O. Another analysis method simply determined that 6.40 g of the 20.

Calculation of Percent Composition

To determine the percent composition of a compound from its combustion products, you need to calculate the masses of its constituent elements from the masses of the combustion products. You then divide the mass of each element by the total mass of the compound and multiply the result by 100.

Explanation

To find the percent composition of the original compound, you first need to find the amounts of carbon and hydrogen in the compound. When the 20.00g of the compound underwent combustion, it produced 44.04 g CO2 and 14.32 g of H2O. By using the molar masses of carbon dioxide (CO2) and water (H2O), you can find that CO2 consists of 27.29% carbon and H2O consists of 11.19% hydrogen. To determine the masses of the elements, we multiply the percentage obtained by the amount of compound used. Example 44.04g CO2 * 27.29% gives us the amount of Carbon and 14.32g H2O * 11.19% gives us the amount of Hydrogen. The remainder of the original mass can be assigned to oxygen.

Now that we know the amounts of each element, we can now calculate the percent composition of the compound, which is simply the mass of each element divided by the total mass of the compound and multiplied by 100.