1. Put on your goggles.
2. Weigh out 1.0 g of CaCl2·2H2O and put it into the 100-mL beaker. Add 25 mL of distilled water and stir to form the calcium chloride solution. Use only distilled water since tap water may have impurities that interfere with the experiment.
3. Use stoichiometry to determine how much Na2CO3 you will need for a full reaction.
4. Weigh the calculated amount of Na2CO3 and put it in a small paper cup. Add 25 mL of distilled water and stir to make a sodium carbonate solution. 5. Pour the sodium carbonate solution from the paper cup into the beaker with the calcium chloride solution. A precipitate of calcium carbonate will form instantly.
6. Use the following instructions to set up a filtration assembly.
●Set a small paper cup inside a slightly larger coffee cup or similar to give the paper cup support and prevent it from tipping over when you add a funnel. ● Fold a sheet of filter paper in half and then in half again as illustrated. Weigh it. ● Open one section of the folded filter paper as shown in the bottom illustration. ● Place the opened filter paper into the funnel and the funnel into the paper cup supported by the coffee cup.
7. Swirl the contents of the beaker to dislodge any precipitate from the sides. Then, while holding the filter paper in place and open, slowly pour the content of the beaker into the filter Paper lined funnel. Be careful to not let the solution overflow the level of the filter paper while pouring. 8. Measure out 2 to 5 mL of distilled water into the graduated cylinder. Pour this down the sides of the beaker, swirl, and pour into the filter paper-lined funnel. 9. After all the liquid has drained from the funnel, lay the filter paper containing the precipitate on folded layers of paper towels and put this someplace where it will not be disturbed while the filter paper and its contents air-dry.
Depending upon the humidity in your area this might take several hours or days. 10. When the filter paper and the precipitated calcium carbonate are completely dry weigh them, subtract the original weight of the empty filter paper, and record the net weight of the calcium carbonate. This is your actual yield of calcium carbonate. 11. Now calculate the percent yield, using your theoretical yield and actual yield. Make sure to show all stoichiometric calculations and all data in your lab report.
Na2CO3(aq) + CaCl2. 2H2O(aq) → CaCO3(s) + 2NaCl(aq) + 2H2O
Data, observations, calculations:
CaCl2.H2O = m/M
= 0.0068 mol
CaCO3 = 0.0068*1/1
= 0.0068 mol
CaCO3 = CaCO3 mol *CaCO3 g
=0.0068 mol*100.01 g
.0068 mol of CaCO3 *100.06 g CaCO3/1mol of CaCO3
=0.6804 g of CaCO3
A. From your balanced equation what is the theoretical yield of your product?
Theoretical yield 0.6804 g of CaCO3
B. According to your data, what is the actual yield of the product?
Actual yield 0.8g CaCO3
C. What is the percent yield?
Percent yield 117%
D. A perfect percent yield would be 100%. Based on your results, comment on your degree of accuracy and suggest possible sources of error.
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. How could these errors be reduced in the future?
This error could be reduced in the future by letting the mixture dry for a few days to make sure it is completely dry.
In conclusion, this was an interesting lab to perform. Although I wish I could have gotten a percentage yield without errors, I’m still happy with my results. It was difficult at first to figure out the theoretical yield, how much Na2CO3 was needed. But once I figured out what I had to do, it was smooth sailing from there on. Overall, it was cool watching the precipitate form instantly and I’m glad I was able to perform this lab to help me get a better insight into stoichiometry and reactions with precipitation.