September 23rd : Determining a Percentage Yield

Determining a Percentage Yield

Today, during this flipped unit of stoichiometry, the class worked on the experiment "Determining a Percentage Yield", in Section 1.31.

Equation used: CuSO₄ (aq) + Fe (s) → FeSO₄ (aq) + Cu (s)

Purpose of Lab: By using the equation above, the purpose of the lab was to find the percentage yield by calculating the potential mass of copper that could be created in relation to the actual mass that was created. The lab therefore had two parts - one in the lab, finding the actual yield of copper and one using our previous knowledge on Reacting Masses and limiting reagents to discover the theoretical yield.

Finding the Actual Yield of Copper:

1. An empty beaker was weighed and recorded
2. 6.0g of copper sulphate pentahydrate was placed in the beaker
3. 50ml of distilled water was added to this beaker
4. The beaker was heated to dissolve the crystals using a Bunsen burner
5. When the beaker was no longer being heated, 1.0g of iron filings were added while stirring
6. The beaker needed to cool, which gave time for calculations to determine the theoretical yield
7. The beaker was then drained from its liquid, keeping the newly made copper at the bottom 
8. It was then put in the oven to remove as much water as possible 
9. The beaker containing the copper was weighed

Finding the Theoretical Yield of Copper:

1.              1.    The number of moles of copper sulphate and iron were determined

     2.       From the equation and this calculation, we were able to establish the limiting reagent.   

[Example of Problem using Limiting Reagents]

       3. Working out the mass of copper (see steps 1-3 for reacting masses help)

Finding the Percentage Yield: 

Actual Yield/Theoretical Yield x 100 = Percentage Yield

Uncertainties and Errors:

Many people, including myself, ended up with a percentage yield higher than 100%. This is most likely because of the remaining water that did not have time to fully evaporate; this error is mostly caused by the limited time we have in class to do these labs as accurately as we could. 

Homework: Finish calculations and extra problems on limiting reagents on the back of the lab.