Unit 7 - Relating how much to how many- Stoichiometry Part 1

When baking banana bread the right ingredients in the right proportions are necessary. Also in a chemical reaction the right reactants at the right proportions must be present to obtain the desired amount of product. The amounts above are for one loaf of banana bread. How many bananas are needed if you wish to make 5 loaves? If you work in a bakery and want to make 200 loaves how much flour would you need? Would you measure that amount in cups or would you measure it in pounds? If you can figure this out stoichiometry will be a piece of cake!

Click on the picture for a tasty recipe

Equations representing chemical reactions relate numbers of particles (molecules or formula units) to weighable amounts of these particles.

The fact that proportional relationships exist between the numbers of particles involved in a chemical reaction allows us to make predictions about “how much stuff” will be required or produced. The reasoning of stoichiometry is best understood in the context of the whole reaction process, which is organized in the BCA table. This table stresses the proportional relationships that exist between moles of reactants and products, discouraging a formulaic approach designed to “get the right answer”. Since we don't have “mole-meters”, conversions to or from moles are simply about the convenience of dealing with quantities we can measure. These calculations are secondary to the mole relationships indicated by the balanced chemical equation.

Chemistry
2008-09
Dr. Michael M. Krop High School

Unit 7 Materials

Stoichiometry is one of the fundamental principles of the chemical industry. A chemical plant which produces a valuable chemical must combine the right amount of raw materials (reactants) to maximize the amount of product with the minimum cost. A chemical plant is not very different from a bakery. In chemistry, however, the recipe for the products come from the balanced chemical equation.

Notice how Stoichiometry can be used to predict the amounts involved in a chemical reaction but it does not give you information in how to make the reaction happen.