Here Comes the Fuzz here_comes_the_fuzz_lab2013b

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Transcript Here Comes the Fuzz here_comes_the_fuzz_lab2013b

Here Comes the Fuzz Lab
Here Comes the Fuzz Lab
Essential Question:
How much product can a chemical
reaction yield?
What limits the yield of a chemical
reaction?
How accurate are stoichiometric
predictions?
Start Lab
• Do Day 1 Procedures before the Prelab
Analysis.
MSDS & LD50s
• MSDS = Material Safety Data Sheet
• LD50 = Lethal Dosage for 50% of test
animals.
• Search for MSDS resource links to
determine the LD50 of copper(II) chloride
& hydrochloric acid. (Google Search).
Prelab Analysis
Part A. The Balanced Chemical Equation:
___+_______*2H2O ___ + ______ + H2O
.
The reaction is a single replacement
reaction using the lowest possible
charge.
Prelab Analysis
Part B Predicting Quantities
Given the mass of iron added to the reaction:
a. Determine the mass of copper that can be produced.
b. Determine the mass of CuCl2*2H2O that would react
with the iron.
Fe + CuCl2*2H2O  Cu + FeCl2 + H2O
~2.5g
b.?g
a. ?g
Prelab Analysis
Part B Predicting Quantities (continued)
Given the mass of iron added to the reaction:
a. Determine the mass of copper that can be produced.
b. Determine the mass of Fe that would react with the iron.
Fe + CuCl2*2H2O  Cu + FeCl2 + H2O
b. ?g
~4.00g
a. ?g
Determining the Limiting Reactant
• What 2 substances are reactants?
• What is the only product we calculate in
the lab?
• Which reactant theoretically produces the
least product?
• Is there enough of the CuCl2*2H2O to
react completely with the Fe?
• Is there enough Fe to react completely
with the CuCl2*2H2O?
Writing the Hypothesis
• Write the hypothesis trusting that the Limiting
Reactant determines the outcome.
• If ____ grams of (limiting reactant) are allowed
to react with ____ grams of (excess reactant),
• then ____ grams of (product) will be produced
and ____ grams of (excess reactant) will be left
over
• because …
Appropriate Procedures
Day 1
__0. Check off each step as you go.
__1. Always use the same scale to avoid
systematic error.
__2. Record observations at each step.
__3. Prepare an organized table of
measurements and observations.
__4. Label plastic cup with period & initials
__5. Mass the dry clean plastic cup.
Day 1 (continued)
__6. Use 2 nails
__7. Sand the iron nails clean before the
reaction.
__8. Record the mass of the 2 nails once.
__9. Measure about but not exactly 4.00g
+/-.01g of CuCl2*2H2O into your plastic cup.
__10. Add 50 ml of distilled water to the cup.
__11. Place the nails in the copper (II) chloride
solution.
__12. Allow the reaction to sit over night to
reach completion.
Day 2
__Put on goggles before obtaining your
sample.
__Make detailed observations of your
experiment before moving forward
__13. Use tongs to remove the iron nails and
place them on a paper towel to dry.
__14. Record the mass of the 2 nails again at
the end when they are dry.
__15. Carefully decant the remaining liquid into
the waste bucket saving the solid precipitate.
Day 2 (continued)
__16. Clean the solid copper residue 3
times total with
___a. With a 25 ml rinse of distilled water.
___b. With a 25 ml rinse of 1M HCl. (waste
bucket!)
___c. Rinse one last time with another 25
ml of distilled water.
****Decant carefully after each rinse.
__17. Place the solid copper residue and
plastic cup on the counter to dry overnight.
Day 3 – Record all observations
__18. Remass the plastic cup and its dry
contents.
__19. Show the instructor your recovered
copper and recycle it into the designated
container.
__20. Dispose of your plastic cup out
thoroughly for the next lab.
Post Lab Analysis
A. Calculate the amount of iron lost:
Fe(lost) = Fe(before) – Fe(after)
B. Calculate the amount of copper
produced?
Cu = (Cu + Cup) - Cup
Percent Yield & Percent Error
How much Cu did you recover compared to your
calculations?
%Yield Cu = (actual Cu / theoretical Cu)x100%
How close was the mass lost in the nails to what
you predicted?
%Error Fe =
[(actual Fe(lost) – theoretical Fe(lost))/theoretical Fe(lost)]
x 100%
Here Comes the Fuzz Lab Report
(1 of 3)
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Title
Essential Questions
Hypotheses (if, then, leftovers, because…)
Materials (include LD50s)
Procedures (rearranged and edited logically –
don’t copy & paste from powerpoint)
• Data & Observations (Steps, Measurements,
Observations)
Here Comes the Fuzz Lab Report
(2 of 3)
• Analysis/Calculations (8 calculations/ 12 points)
– Item / Strategy-Formula / Work / Answer
– 4 Prelab analysis calculations
– Actual amount of Fe lost
– Actual amount of Cu produced
– % Yield of Cu produced
– % Error of Fe used
• Sources of Error – at least 2 for real issues that
may have thrown off the results (Hints: moisture,
decanting, nails, etc.)
Here Comes the Fuzz Lab
Report (3 of 3)
• Conclusions
A) Revisit & evaluate hypothesis. Support your
evaluation with numbers from the lab.
B) Revisit each of the 3 essential questions.
C) Which was the limiting reactant? Which was the
excess reactant and how could you tell for each?
D) Describe how stoichiometry is used in real life by
professionals. (Hint: Look in Chapter 11)
E) Extra Credit: Relate slang title to lab