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 QuantitiesGiven 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 ProceduresDay 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)

• 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)

• ConclusionsA) 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