CP Chemistry
Theodore Roosevelt High School
Lab #2-6
Limiting Reagents Lab: Turning Iron into Copper
Introduction
As we’ve seen before, it’s possible to predict the number of grams of a
given product that will be formed in a chemical reaction if you know the
mass of any one of the reactants. In this lab, you will start with known
masses of copper (II) sulfate and iron and determine the mass of copper
metal formed by a chemical reaction. However, one of these chemicals
will be completely used up by the reaction – the limiting reagent – and
the other will not, leaving some chemical left over in excess.
Because this reaction could also form either iron (II) sulfate or iron (III)
sulfate, you will use both observations and stoichiometry to determine
the chemical reaction that occurred. Through calculations, you will also
determine the theoretical mass of copper metal that should form from this
reaction and determine its percent yield.
Purpose
To use stoichiometry calculations to calculate theoretical mass and percent yield.
Prediction
Which reactant – copper (II) sulfate or iron – will be the limiting reagent? Explain why you think so.
Equipment
balance
beaker, 250 mL
Bunsen burner
iron ring
permanent marker
ring stand
stirring rod
wire gauze
Materials
copper (II) sulfate (anhydrous) [CuSO4 (s)]
distilled water
filter paper
iron filings [Fe (s)]
Safety Considerations
• Safety goggles must be worn at all times.
• Sometimes chemicals from previous labs still remain in glassware and on other lab equipment.
Wash all lab equipment before and after performing this lab.
Procedure
1.
Measure 7.00 g of anhydrous copper (II) sulfate and place it in a 250 mL beaker.
2.
Add about 50 mL of distilled water and heat gently over a Bunsen burner until the solid has
completely dissolved. DO NOT ALLOW THE SOLUTION TO BOIL.
3.
Once the crystals have dissolved, remove the beaker from the heat. Record your observations of
the solution’s appearance.
4.
Measure 2.00 g of iron filings and slowly add them to the beaker while stirring the hot CuSO4
solution.
CP Chemistry
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Theodore Roosevelt High School
Lab #2-6
Allow this solution to sit for at least 10 minutes. Record your observations of the solution’s
appearance.
Obtain a piece of filter paper and label it with your lab group members’ names using a permanent
marker. Determine and record its mass.
Fold the filter paper in quarters and place it in a funnel, wetting it with distilled water to keep it in
place.
Filter the solution through the funnel and filter paper to collect the copper product. Wash the
product with distilled water. Let the filter paper and copper sit overnight.
After allowing the filter paper to dry overnight, determine and record its mass.
Additional Clean-up and Disposal (after the 2nd day)
1.
Dispose of the copper product in the waste beaker, NOT the trash can.
2.
Dispose of the filter paper in the trash.
Data – you should create a data table in your lab write-up that looks something like this:
Item
Mass (g)
unused filter paper
Calculations (Include these answers in your Conclusion!)
1.
One possible unbalanced chemical equation for this reaction is:
copper (II) sulfate (aq) + iron (s) → copper (s) + iron (II) sulfate (aq)
If this were the correct reaction, what mass of copper should be produced in this lab?
2.
The other possible unbalanced chemical equation for this reaction is:
copper (II) sulfate (aq) + iron (s) → copper (s) + iron (III) sulfate (aq)
If this were the correct reaction, what mass of copper should be produced in this lab?
3.
What mass of copper was formed? What was the percent yield of this reaction?
Questions
1.
What are some of the clues you observed that suggested a chemical reaction occurred?
2.
Which reactant limited the reaction? What observations support this conclusion?
3.
Based on your data, which product was formed along with the copper metal: iron (II) sulfate or
iron (III) sulfate? How do you know?
Errors
Describe two possible errors you may have committed in this lab that may have somehow affected your
results. Explain the specific steps you will take to avoid each of these errors in the future.
Conclusion
Write two or more paragraphs summarizing your results, examining the validity of your prediction, and
explaining your calculations.
CP Chemistry
Theodore Roosevelt High School
Limiting Reagents Lab workspace:
Lab #2-6