Video: Atoms and Structure

In a chemical compound containing carbon, oxygen, and hydrogen, there are equal numbers of carbon and hydrogen atoms. However, the number of oxygen atoms is twice the number of hydrogen atoms. What is the empirical formula of the compound?

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Video Transcript

In a chemical compound containing carbon, oxygen, and hydrogen, there are equal numbers of carbon and hydrogen atoms. However, the number of oxygen atoms is twice the number of hydrogen atoms. What is the empirical formula of the compound?

The empirical formula of a compound tells us the simplest whole number ratio of atoms that are in the compound. Our compound contains carbon, oxygen, and hydrogen. So, we need to figure out the ratio of carbon to oxygen to hydrogen so we can determine the empirical formula of this compound. We’re told that there are an equal number of carbon and hydrogen atoms, which means that the ratio of carbon to hydrogen in our compound is one to one. Then the problem says that the number of oxygen atoms is twice the number of hydrogen atoms. In other words, the ratio of oxygen to hydrogen in the compound is two to one.

If we put both of these pieces of information together, that means that the ratio of carbon to oxygen to hydrogen that’s in this compound is one to two to one. We can’t reduce this ratio any further, which means that it’s already expressed in the simplest whole numbers. So, we can use this ratio to create the empirical formula for the compound, CO2H. Because this formula just tells us the ratio of carbon to oxygen to hydrogen in the compound, that doesn’t necessarily mean that there’s one carbon atom, two oxygen atoms, and one hydrogen atom in the compound.

The type of chemical formula that does tell us that information is the molecular formula, which tells us the amount of each type of atom in the compound, not just the simplest whole number ratio of atoms. But we were just tasked with finding the empirical formula of this compound, which is CO2H.

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