Chemistry Text

Chemistry Text

196

Chemical Proportions in Compounds
ow do chemists use what they know about molar masses? In Chapter 5, you learned how to use the periodic table and the mole to relate the mass of a compound to the number of particles in the compound. Chemists can use their understanding of molar mass to find out important information about compounds. Sometimes chemists analyze a compound that is found in nature to learn how to produce it more cheaply in a laboratory. For example, consider the flavour used in vanilla ice cream, which may come from natural or artificial vanilla extract. Natural vanilla extract is made from vanilla seed pods, shown on the left. The seed pods must be harvested and processed before being sold as vanilla extract. The scent and flavour of synthetic vanilla come from a compound called vanillin, which can be produced chemically in bulk. Therefore its production is much cheaper. Similarly, many medicinal chemicals that are found in nature can be produced more cheaply and efficiently in a laboratory. Suppose that you want to synthesize a compound such as vanillin in a laboratory. You must first determine the elements in the compound. Then you need to know the proportion of each element that is present. This information, along with your understanding of molar mass, will help you determine the chemical formula of the compound. Once you know the chemical formula, you are on your way to finding out how to produce the compound. In this chapter, you will learn about the relationships between chemical formulas, molar masses, and the masses of elements in compounds.
The chemical formula of vanillin is C8H8O3 . How did chemists use information about the masses of carbon, hydrogen, and oxygen in the compound to determine this formula?

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Chapter Preview 6.1 Percentage Composition 6.2 The Empirical Formula of

a Compound
6.3 The Molecular Formula of

a Compound
6.4 Finding Empirical and

Molecular Formulas by Experiment

Concepts and...