Empirical Formula Calculation: How to Determine the Unknown Compound's Formula

Question:

What is the empirical formula of an unknown compound that consists of C, H, and O, based on the combustion data provided?

Answer:

The empirical formula of the unknown compound is CH8O.

Explanation:

To determine the empirical formula of a compound containing carbon, hydrogen, and oxygen, we first need to analyze the combustion results. In this case, from the combustion of 6.40g of the compound, we obtained 15.6g of CO2 and 6.40g of H2O. This data allows us to calculate the moles of each element present in the compound.

First, we find the number of moles of carbon (C) by dividing the mass of CO2 by its molar mass. This gives us 0.354 moles of C. Similarly, we calculate the moles of hydrogen (H) by dividing the mass of H2O by its molar mass, resulting in 0.710 moles of H, as there are two hydrogen atoms in each water molecule.

Next, we determine the mass of oxygen (O) by subtracting the total masses of carbon and hydrogen from the initial mass of the compound. The resulting mass of oxygen is 1.43g, equivalent to 0.089 moles of O.

By dividing each element's mole quantity by the smallest mole quantity (0.089 moles of O), we arrive at the mole ratio of C:H:O as 1:2:8, hence giving us the empirical formula of CH8O for the unknown compound.