Stoichiometry Lab Report: Can You Make Two Grams Sample Report

Below is one example of the lab report for Can You Make 2 Grams?  Additionally are my help students transcribe their notes into paragraph format.

Can you Make Two Grams?

Background: What is a mole?  A mole is 6.02 X 10²³ of atoms; it is also the atomic weights added together to get the molar mass. What is Stoichiometry? Stoichiometry is “relating the quantities of chemical substances in a chemical reaction” (Apologia)

The background section should contain the purpose.  For this lab, I asked the students to define moles and stoichiometry.  I instructed them to use their textbook and cite it using MLA.

Materials: During this lab one uses a Vacuum Filtration Assembly, beakers, scoopulas, spatulas, filters, funnel, wooden stir rods, plastic tray, 4.5 grams of ZnSO₄, 1.7 grams of Na₂CO₃, and 50 mL of distilled water.

In the materials section the student lists the equipment and apparatus. 

Procedures: First the student must measure 25 mL. of water into separate beakers. The student will take the first beaker and add the 4.5 grams of ZnSO₄ into the 25 mL of water and stir. Next one takes the second beaker that has 25 mL. of water and adds 1.7 grams of Na₂CO₃. One takes a large beaker and the student mixes the two substances together and mix until it is well combined. Secondly one weighs the filter for the Vacuum Filtration Assembly. After weighing the filter and writing down the weight (appt. one gram) the student will put the filter in place of the Vacuum Filter Assembly and pours the product into the filter. The student must cautiously watch and make sure the substance does not overflow and get on the funnel. If one gets the substance on the funnel one must carefully scoop it into the filter. So, one gets more of an accurate percent error. Simultaneously the student’s partner should be pumping the Vacuum Filter pump. One pumps until there is no more water dripping into the Side Arm Flask and the substance should look as if it is drying out. After one finishes this step, one takes out the filter and put on a tray for the substance to resume drying. Once the substance and filter are entirely dried one must weigh the substance.

Lastly the student must find the percent error of the lab by subtracting the weight of the finial substance, divide the number by two and multiple that answer by 100 and add a percent sign (%) to find the percent error. The possible percent error on may get from doing this lab is not fully getting the total amount of the 50 mL. of water out of the solution.   

The procedures are usually the most lengthy.  If your child is having difficulty transcribing their actions into a paragraph, have them list the steps.  For example, "The first step is to weigh the two reactants.  The second step is to mix each compound in a beaker with 25 mL of water.  Students have difficulty using the third person and present tense.  Watch for errors such as, "Mix the solution or Weigh the zinc sulfate."  These two examples use the imperative and are not in third person.  

Equation:

ZnSO₄ X 7H₂O + Na₂CO₃ -> ZnCO₃ + Na₂SO4 + 7H₂O

The equation may be written as zinc sulfate heptahyrate and sodium carbonate yield the products zinc carbonate, sodium sulfate, and water.  The product, zinc carbonate, is the precipitate.

Data: The results are 2.6 grams.  The percent error is 30%.

The word, data, is plural.  The data are 2.6 grams of the precipitate zinc carbonate.  In the data section, the student includes the results, a data table, and the percent error.  

Discussion:  2.6 grams are left due to the fact we were unable to complete retrieve all the water from the solution in one round, as well the substances were not entirely dry after 2 weeks.

Students list sources of error in the discussion section.  For example, some of the precipitate was lost in the filtrate.  The precipitate contains water and its mass exceeds two grams.  The digital scale is accurate to the nearest tenth.  A scale accurate to the nearest hundredth produces more accurate results.

Conclusion: More test must be performed to get more accurate results.

The lab takes 45 minutes to pump the products through the filtration assembly.  For practical reasons the students perform one trial.  Labs are performed a minimum of three trials.

Citation:

Exploring Creation with Chemistry 2^nd edition, Wile Apologia Educational Ministries, Inc. 2003

The students use MLA format for the citation.