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
Dr. Michael M. Krop High School
Unit 7 Materials
Worksheet 1 - Mole Relationships - BCA
Worksheet 2 - Stoichiometry and Percent Yield
Worksheet 3 - Adjusting to Reality
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.