Honors Chemistry Notes

Name: ______Date: ______Mods: ______

Unit 7: Stoichiometry

Imagine Baking Cupcakes:

432 g mix + 1 cup water + ½ cup oil + 3 eggs12 cupcakes

  • In order to produce the 12 intended cupcakes, these “reactants” must be combined in the appropriate ratios every time.
  • If we had 9 eggs that we wanted to use up, we would be able to calculate the amount of each other “reactant” that we would need as well as the number of cupcakes we would be able to produce as a result. This is essentially what stoichiometry is:

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Stoichiometry:the relationship between the relative quantities of substances taking part in a chemical reaction .

1 CH4 (g) + 2 O2 (g)  1 CO2 (g) + 2 H2O (g)

  • Due to the Law of Conservation of Mass, the coefficients in any balanced chemical equation represent the number of reactant molecules needed to produce a specific quantity of product molecules.
  • Whether you are counting individual molecules or, more likely,moles of molecules, the ratio of reactants to products is always the same for a balanced reaction; this is known as the molar ratio.
  • Chemists use these molar ratios in order to calculate the amount of product that can be formed when a specific amount of reactant is used (or vice-versa)

Stoichiometry Examples:

Reaction:The combustion of liquid tetracarbondecahydride (common name: butane)

Balanced Equation:

a)Mole A  Mole B

How many moles of butane are necessary to completely react with 6.2 moles of oxygen gas?

b)Mole A  Mass B

How many grams of carbon dioxide are formed if 11.5 moles of water is produced?

c)Mass A  Mole B

How many moles of oxygen gas are needed to produce 5.6 g of water?

d)Mass A  Mass B

Calculate the mass of carbon dioxide produced when 1.45 g of butane are burned.

e)Mass A Atom B

How many hydrogen atoms (from water) would be formed when 88 g of carbon dioxide is produced in this reaction?