Unit 8 - Stoichiometry

Introduction:

Unit 8 is by-far the hardest chapter of the year. If you haven't given 100% effort thus far, you better give

that effort during this chapter. Unit 8 introduces the concept of stoichiometry, which is a quantitative

study of the amount of reactants consumed and products formed. Math skills and critical thinking will be key to success in this chapter, as will practicing the problems on your own. By the end of this chapter, you should be

able to take some quantity of two reactants and predict the products formed, how much of each product will be formed and which reactant will run out first.

Student Objectives - Unit 8:

8.1

a. Reaction stoichiometry involves the mass relationships between reactants and products in a chemical reaction.

b. Relating one substance to another requires expressing the amount of each substance in moles.

c. A mole ratio is the conversion factor that relates the amount in moles of any two substances in a chemical reaction.

d. Amount of a substance is expressed in moles and mass of a substance is expressed by using mass units such as grams, kilograms or milligrams.

e. Mass and amount of substance are quantities, whereas moles and grams are units.

f. A balanced chemical equation is necessary to solve any stoichiometric problem.

8.2

a. In an ideal stoichiometric calculation, the mass or the amount of any reactant or product can be calculated if the balanced chemical equation and the mass or amount of any other reactant or product is known.

8.3

a. In actual reactions, the reactants may be present in proportions that differ from the stoichiometric proportions required for a complete reaction in which all of each reactant is converted to product.

b. The limiting reactant controls the maximum possible amount of product formed.

c. For many reactions, the quantity of a product is less than the theoretical maximum for that product. Percentage yield shows the relationship between the theoretical yield and actual yield for the product of a reaction.

Ohio Department of Education - Chemistry Standards:

A stoichiometric calculation involves the conversion from the amount of one substance in a chemical reaction to the amount of another substance. The coefficients of the balanced equation indicate the ratios of the

substances involved in the reaction in terms of both particles and moles.Once the number of moles of a

substance is known, amounts can be changed to mass, volume of a gas, volume of solutions and/or number of particles. Molarity is a measure of the concentration of a solution that can be used in stoichiometric calculations. When performing a reaction in the lab, the experimental yield can be compared to the theoretical yield to

calculate percent yield. The concept of limiting reagents is treated conceptually and not mathematically. Molality and Normality are concepts reserved for more advanced study.

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