# Stoichiometry of a Precipitation Reaction

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Stoichiometry of a Precipitation Reaction
Title: Stoichiometry of a Precipitation Reaction

Purpose: The purpose is to predict the amount of precipitation using stoichiometry. Another purpose is to measure and calculate percentage yield.

Procedure:
1. Weigh out 1.0g of CaCl2*2H2O and put it into a 100mL beaker.
2. Add 25mL of distilled water and stir.
3. Using stoichiometry to determine how much Na2CO3 is needed for a full reaction.
4. Weigh the calculated amount and put it in a small paper cup. Add 25mL distilled water and stir.
5. Pour this solution into the beaker and watch as a precipitate forms instantly.
6. To set up a filtration assembly:
a. Set a small paper cup inside a slightly larger coffee cup.
b. Fold a sheet of paper in half and then in half again.
c. Open one section of the folded filter paper.
d. Place the opened filter paper into the funnel, and the funnel into the paper cup.
7. Swirl the contents of the beaker.
8. Pour the contents of the beaker into the funnel.
9. After there is no more liquid in the funnel, take the filter paper and lay it somewhere to air dry.
10. When the contents are completely dry, weigh it.
11. Subtract the original weight of the filter paper. The remaining weight will be your actual yield of calcium carbonate.
12. Calculate the percent yield.
13. Clean up all remaining chemicals.

Observations:

CaCl2.H2O = m/M
= 1/147
= 0.0068 mol
CaCO3 = 0.0068*1/1
= 0.0068 mol
CaCO3 = ?
CaCO3 = CaCO3 mol *CaCO3 g
=0.0068 mol*100.01 g
=0.68 g

Theoretical Yield:
.0068 mol of CaCO3 *100.06 g CaCO3/1mol of CaCO3
=0.6804 g of CaCO3

Percentage Yield:
= (0.8/0.68)*100
=117%

Na2CO3(aq) + CaCl2. 2H2O(aq) → CaCO3(s) + 2NaCl(aq) + 2H2O

Questions:
A. Theoretical yield: 0.6804 g of CaCO3
B. Actual yield: 0.8g CaCO3
C. Percent yield: 117%
D. My percentage yield was far more than the expected 100%. An explanation would be that there was water left over on the precipitate that added to its extra weight.
E. This error could be

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