Student Behavioral Objectives
The student will:
- define theoretical and actual yield.
- explain the difference between theoretical and actual yield.
- calculate percent yield (reaction efficiency).
Timing, Standards, Activities
Timing and California Standards
Number of 60 min periods
Activities for Lesson 4
1. Percent Yield Worksheet
Answers for Percent Yield (L4) Review Questions
Sample answers to these questions are available upon request. Please send an email to firstname.lastname@example.org to request sample answers.
Multimedia Resources for Chapter 14
This website provides a stoichiometry game.
This website contains various resources, including PowerPoint lectures, on many topics in chemistry, including one on stoichiometry.
This website has lessons, worksheets, and quizzes on various high school chemistry topics. Lesson 9-3 is on solving mass-mass problems.
This website has several video lessons on performing stoichiometry calculations, including problems with a limiting reactant.
This video is an electronic blackboard presentation of the calculation of a percent yield.
Laboratory Activities for Chapter 14
Teacher's Pages for Mass-Mass Relationships in a Chemical Change
Lab – Mass-Mass Relationships in a Chemical Change
When chemical reactions occur, the amount of product created can be theoretically predicted if you know the amounts of reactant used. This phenomenon is based on the law of mass-energy conservation. Since you cannot create or destroy matter in a chemical change, the sum of the masses of reactants and the sum of the masses of products must be equal. For example:
The purpose of this activity is to study the relationships between the numbers of moles of reactant used, number of moles of products obtained, and coefficients used to balance a chemical reaction.
Apparatus and Materials
- Evaporating dish
10 mL graduate
- Watch glass
- Disposable pipette
- Electronic balance
- Goggles and apron
- Electric Oven
- Weigh a clean, dry evaporating dish + watch glass on the electronic balance. Record the mass.
- Weigh out 2.0 g±0.10 g of NaHCO3 into the evaporating dish, and record the mass.
- Measure 5.0 mL of 6 M HCl into a 10 mL graduate.
- Place the watch glass on top of the evaporating dish, curve side down. Then add the HCl through the remaining opening by transferring it with a disposable pipette. Add all of it. Swirl the dish slowly. Record what you see. The reaction is complete when no solids remain. Add more acid drop wise if the reaction is not complete.
- Place the dish, the liquid, and the watch glass into an 110∘C oven for 24 hours.
- Record the mass of the dish, the watch glass, and the remaining residue. Record this mass.
Mass of empty dish + watch glass ___________________g
- From your balanced equation, what is the mole ratio between the NaHCO3 and NaCl? How does it compare with the mole ratio from your experiment?
- Suppose you had started with 20 moles of NaHCO3, how many moles of NaCl would you expect to be formed? Explain.
- Do the results of your experiment support the law of conservation of mass-energy? Explain.