CHEM 2115
Name
Limiting Reagent Lab Report #5
________________
Section #
Chem I Lab
Station #
Date
.
Overall equation: CaCl2 (aq) + K2C2O4•H2O (aq) ⇒ CaC2O4•H2O (s) + 2 KCl (aq)
Net Ionic Equation: Ca+2 (aq) + C2O4 -2 (aq) + H2O (l) ⇒ CaC2O4 • H2O (s)
1. Data & Calculations :
CaCl2
K2C2O4•H2O
Concentration of solution__________
Mass assigned__________
Volume of solution____________
Mass used____________
Moles of CaCl2 used_____________
Moles of K2C2O4•H2O used_____________
(MW = 184.24 g/mol)
Crucible and filter mass
CaC2O4•H2O (Precipitate)
Dry (crucible + filter) __________
Mass of CaC2O4•H2O recovered_________
With Precipitate _____________
Moles of CaC2O4•H2O recovered_________
(MW = 146.12 g/mol)
Attach sample calculations of each type necessary to obtain the results in the above table. These should include the equations used,
substituted values, and results.
2. Excess and Limiting Tests:
2a. Did a precipitate form (1) when K2C2O4 solution was added to the filtrate?_____
2b. Based on the results shown in 2a, what was the limiting reactant? ________
(2) when CaCl2 solution was added?_____
What was the excess reactant? ___________
3. Comparison between theory and experiment:
a. Based on the number of moles of each reactant you started with, determine which was the limiting reactant. What was
the excess reactant? Show your work in the space below.
b. Does your result from question 3a agree with the answer in 2b? If these do not agree, comment on why not.
c. According to the balanced chemical equation and the amounts of reactants used in this experiment, how many moles of
the precipitate should you have obtained (in theory)? What is the percent yield of product? Be show to show your
calculations either below or on a separate sheet.
4. Questions: What if…? Predict the effect of the following experimental problems on the experimental percent yield of
CaC2O4•H2O by telling whether it will increase, decrease, or remain unchanged. Explain why.
a. The CaC2O4•H2O precipitate was still wet when you recorded the mass of the crucible and precipitate.
b. The filtrate was cloudy indicating some of the solid passed through the filter paper.
c. Before starting the experiment the crucible had some solid leftover from a previous student that you did not remove.
5. Class data: Students in this experiment used different amounts of potassium oxalate. The class results are given in an Excel
spreadsheet on Blackboard. Plot the data as an XY (Scatter) graph with moles potassium oxalate used on the X-axis and moles
calcium oxalate precipitate recovered on the Y-axis. (To do this, you may have to convert the masses of potassium oxalate and
calcium oxalate to moles, the molecular weights are given above and in the lab manual.) Try to adjust the Y-axis scale to best
visualize your data.
Submit your plot with this lab report. To help interpret your plot, a copy of a plot of the course data from Fall 2008 is
available on the course blog. Observe your data and comment on the results:
a. Are there any outlier points that do not fit with most of the data? Comment on them.
b. In the region of small amounts of potassium oxalate, does your section data show that the moles of calcium oxalate
precipitate recovered increases, decreases, or remains fairly constant as the number of moles of potassium oxalate
increases? Explain this result using the concept of limiting reactants.
c. In the region of large amounts of potassium oxalate, does your section data show that the moles of calcium oxalate
precipitate increase, decrease, or remain fairly constant at the number of moles of potassium oxalate increases?
Explain this result using limiting reactant theory.
d. If your answers to questions 5b and 5c are different, tell at what experimental value of moles potassium oxalate the data
show a change?
e. Compare your answer to question 5d with the number of moles of calcium chloride used in this experiment. Are they
nearly the same? Explain.