CH141 Laboratory



CH141 Lab Section




Report for Experiment 3 – Precipitation Reactions and Stoichiometry


Use complete sentences, use the proper number of digits and/or significant figures, and include units. Erase all the words in italics and type your answers/information into this template (your text/answers shouldn’t be in italics).


Introduction: 2-sentence maximum; state the scientific purpose of the experiment. Describe the method you will use, in a general sense. Do not discuss the experimental procedure details or data analysis steps. We wrote the Introduction section for you this week . No additions are necessary.


An unknown alkali metal carbonate salt was reacted with aqueous calcium chloride to form a precipitate. By using measured masses and stoichiometric relationships, the identity of the precipitate and the starting alkali carbonate salt could be identified.


Procedure : Give a brief description of the experimental procedure (a few sentences is sufficient, you do not need to write a full procedure). Reference the experiment handout on the CH141 website. List any changes from the written procedure on the handout (if any).


Results : Please erase the bullets from the list below when you erase the italicized words. All tables should be numbered and have a title.


         Provide a table of all quantities that you measured during the laboratory (masses, volumes, etc.) and any values that you calculated from those quantities.  Label your table and remember to include units on your quantities.

         Provide a labeled plot that shows the stoichiometric relationship between the amount of your carbonate salt and the amount of precipitate. Make sure to include a title, have two labeled axes, include applicable units, and give trend-lines and corresponding R 2 value for each trendline. Clearly label your data point on the plot.

         Identify your precipitate. Write the balanced chemical reaction that enabled this precipitate to form.

         Based on your mass of precipitate, calculate your isolated yield of product.






Discussion : Please erase the bullets from the list below when you erase the italicized words. When citing results r efer to each Table/Figure with an explicit reference as necessary (e.g. see Table 1) in the relevant part of this section.


In paragraph form, provide a short discussion of the following topics. Make sure your discussion section does not exceed one typed page (no smaller than 12-point font).


         Explain what you graphed for the group data (for your carbonate salt) and the resulting shape of the graph.

         What is the significance of the slopes of the lines?  What is the significance of the intersection of the two lines?

         How does your graph and/or trendline(s) indicate what the precipitate is?

         Identify your starting carbonate salt. What information did you use to discover the identity?

         Compare and contrast your group graph to the data (and graphs) for the other two carbonate salts. Is the precipitate the same for all groups? How do you know?




Attach a copy of any additional graph(s) that you made/used in order to interpret the provided data from the other two carbonate salts. Remember to include a title for each attached figure.