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Stoichiometry

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Determining the Limiting Reactant and Percent Yield in a Precipitation Reaction

Objectives: • Observe the reaction between solutions of sodium carbonate and calcium chloride. • Determine which of the reactants is the limiting reactant and which is the excess reactant. • Determine the theoretical mass of precipitate that should form. • Compare the actual mass with the theoretical mass of precipitate and calculate the percent yield.

Materials: Balance 0.70 M sodium carbonate solution, Na2CO3(aq) Graduated cylinder 0.50 M calcium chloride solution, CaCl2(aq) Beaker (250 mL) Wash Bottle (distilled H2O) Filter paper Funnel Iron ring Ring stand

Procedure:

Part I: The Precipitation Reaction (Day 1) 1. Obtain two clean, dry 25 mL graduated cylinders and one 250 mL beaker.

2. In one of the graduated cylinders, measure 25 mL of the Na2CO3 solution. In the other graduated cylinder, measure 25 mL of the CaCl2 solution. Record these volumes in your data table.

3. Pour the contents of both graduated cylinders into the 250 mL beaker and observe the results. Record these qualitative observations in your observations table. Allow the contents of the beaker to sit undisturbed for approximately 5 minutes to see what happens to the suspended solid particles. Meanwhile, proceed to step 4.

4. Obtain a piece of filter paper and put your initials and your partner’s initials on it using a pencil. Measure and record the mass of the filter paper, then use it to set up a filtering apparatus.

5. Gently swirl the beaker and its contents to suspend the precipitate in the solution, then pour it carefully and slowly into the filter funnel. It takes time to complete the filtering process so plan to do it in stages. Use the wash bottle to rinse the remaining precipitate form the beaker into the funnel.

6. Use the wash bottle one last time to

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