EXPERIMENT

Stoichiometry of a

Precipitation Reaction

Hands-On Labs, Inc.

Version 1.0

Review the safety materials and wear goggles when

working with chemicals. Read the entire exercise

before you begin. Take time to organize the materials

you will need and set aside a safe work space in

which to complete the exercise.

Experiment Summary:

Students will learn about precipitation reactions.

They will learn how to use stoichiometry to predict

the quantities of reactants necessary to produce

the maximum amount of precipitated product.

Finally, students will calculate percent yield from a

precipitation reaction and determine conservation

of mass.

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© Hands-On Labs, Inc.

Stoichiometry of a Precipitation Reaction

Learning Objectives

Upon completion of this laboratory, students will be able to:

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Identify and define the parts of a chemical reaction, including the reactants and products.

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Define the term stoichiometry, and discuss the importance of accurate calculations in

experimental design and outcome.

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Describe how the molar quantity of a substance is related to its molecular weight and

calculate the molar quantity of various substances.

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Identify the defining characteristics of a precipitation reaction.

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Predict and calculate the theoretical maximum amount of product produced in a

precipitation reaction, using stoichiometry.

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Describe the difference between theoretical and actual yield.

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Calculate the percent yield of a reaction.

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Conduct an experiment in which two reactants form a precipitate.

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Utilize scientific laboratory resources to accurately measure, mix, weigh, and analyze

experiment materials and results.

Time Allocation: 2.5 hours + an overnight drying period

Let’s say we decided to run this experiment again. This time we used 1.0 gram of CaCl2·2H2O and 1.0 gram of Na2CO3. How many grams of CaCO3 would we produce? Please show/explain how you found your answer.

Of the two reactants in the experiment, one was the limiting reagent and the other was the excess reagent. Calculate the grams of the excess reagent still remaining in solution (using the amounts from the lab procedures).

What if we ran the experiment and used 1.5 grams CaCl2·2H2O and 1.0 gram Na2CO3.  Show how many grams of CaCO3 would be produced.

Before the advent of Advil and Tylenol, did people simply have to “grin and bear it” when it came to pain?  One of the most common ancient medicines for pain, fever, and inflammation came as a byproduct of the willow tree. While the first uses date back to 400 BCE, American historians cite the use of willow bark tea by the Lewis and Clark exploration party in the early 1800’s. Salicylic acid derived from the willow tree’s bark was the key chemical involved with the relief of pain and the reaction to make aspirin is a fairly simple one performed in numerous chemistry classrooms nationwide.

Aspirin can be made by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4).

C4H6O3  + C7H6O3 –> C2H4O2  + C9H8O4

When synthesizing aspirin, a student began with 3.05 mL of acetic anhydride (density  = 1.08 g/mL) and 1.85 g of salicylic acid. The reaction was allowed to run its course and 1.84 grams of aspirin was collected by the student. Determine the limiting reactant, theoretical yield of aspirin, and percent yield for the reaction.

In this lab, calcium carbonate was a precipitate.  Use the solubility rules in Table 4.1 of your textbook to predict if the following reactions will form precipitates.  If the reaction does not form a precipitate write “no reaction”.  For the reactions that form a precipitate, write the balanced chemical equation and the net ionic equation for the reaction.

cobalt (II) nitrate and sodium iodide

cobalt (II) nitrate and sodium phosphate

barium nitrate and sodium sulfate

nickel nitrate and sodium chloride

copper (II) nitrate and sodium carbonate