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Empirical FormulasWe dealt with empirical formulas way back in the first term of this course. Let me remind you what they are, in case your memory of them has faded. Empirical formulas show the simplest ratio of the atoms of different elements in a compound. This ratio is based on experimental (empirical) data about the composition of that compound. As an example, let me use a compound we will study in the next lesson, benzene. Molecules of benzene contain six carbon atoms and six hydrogen atoms. Thus, the molecular formula is C6H6. But from the composition by weight (92.3% C and 7.7% H) all we can tell is that there is one carbon atom for every hydrogen atom. Thus, the empirical formula is CH. In the field of organic chemistry, empirical formulas are not used much. They serve only as a starting point from which to determine the molecular and structural formulas. In order to figure out the molecular formula from the empirical formula, you need more information. You need to know the molecular weight or perhaps something about the bonding arrangements or valences of the atoms.
E-mail instructor: Eden Francis Clackamas Community College |
