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DEMONSTRATION in Percent Yield, Classification of Reactions, Limiting Reactant, Chemical Change. Last updated April 26, 2019.


Summary

In this demonstration, students see evidence of a chemical reaction. Usually done on the first day of school, this activity gets AP Chemistry students back into chemistry mode.

Grade Level

High school

AP Chemistry Curriculum Framework

  • Big Idea 1: The chemical elements are fundamental building materials of all matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions.
    • 1.1 The student can justify the observation that the ratio of the masses of the constituent elements in any pure sample of that compound is always identical on the basis of the atomic molecular theory.
    • 1.2 The student is able to select and apply mathematical routines to mass data to identify or infer the composition of pure substances and/or mixtures.
    • 1.3 The student is able to select and apply mathematical relationships to mass data in order to justify a claim regarding the identity and/or estimated purity of a substance.
    • 1.4 The student is able to connect the number of particles, moles, mass, and volume of substances to one another, both qualitatively and quantitatively.
    • 1.18 The student is able to apply conservation of atoms to the rearrangement of atoms in various processes.
    • 1.19 The student can design, and/or interpret data from, an experiment that uses gravimetric analysis to determine the concentration of an analyte in a solution.
  • Big Idea 3: Changes in matter involve the rearrangement and/or reorganization of atoms and/or the transfer of electrons.
    • 3.1 Students can translate among macroscopic observations of change, chemical equations, and particle views.
    • 3.2 The student can translate an observed chemical change into a balanced chemical equation and justify the choice of equation type (molecular, ionic, or net ionic) in terms of utility for the given circumstances.
    • 3.3 The student is able to use stoichiometric calculations to predict the results of performing a reaction in the laboratory and/or to analyze deviations from the expected results.
    • 3.4 The student is able to relate quantities (measured mass of substances, volumes of solutions, or volumes and pressures of gases) to identify stoichiometric relationships for a reaction, including situations involving limiting reactants and situations in which the reaction has not gone to completion.
    • 3.5 The student is able to design a plan in order to collect data on the synthesis or decomposition of a compound to confirm the conservation of matter and the law of definite proportions.
    • 3.8 The student is able to identify redox reactions and justify the identification in terms of electron transfer.
    • 3.10 The student is able to evaluate the classification of a process as a physical change, chemical change, or ambiguous change based on both macroscopic observations and the distinction between rearrangement of covalent interactions and noncovalent interactions.
  • Big Idea 5: The law of thermodynamics describe the essential role of energy and explain and predict the direction of changes in matter.
    • 5.10 The student can support the claim about whether a process is a chemical or physical change (or may be classified as both) based on whether the process involves changes in intramolecular versus intermolecular interactions.

Objectives

By the end of this lesson, students should be able to

  • Identify signs of a chemical change.
  • Recognize a single replacement reaction.

Chemistry Topics

This lesson supports students’ understanding of

  • Chemical change
  • Limiting reagents
  • Classification of reactions
  • Percent yield

Time

Teacher Preparation: 10 minutes

Lesson: 30 minutes

Materials

  • Copper wire
  • Known concentration of silver nitrate
  • Graduated cylinder
  • Beaker

Safety

  • Always wear safety goggles when working in a lab setting.

Teacher Notes

  • Record the mass of Cu before the experiment. Note the volume and molarity of the AgNO3 solution.

Analysis answers

  • Evidence of a chemical reaction: Copper wire gets “furry” and solution turns blue
  • Type: single replacement
  • Why: copper ionizes (aq/blue) and silver ions become silver metal (solid)
  • Remaining answers are dependent on mass of copper and molarity and volume of AgNO3 used. Note: this is a limiting reagent problem.

For the Student

Lesson

Background

Your teacher will place copper wire into a silver nitrate solution.

Prelab question

Will a reaction occur and how do you know?

Analysis

  1. What evidence is there of a reaction?
  2. What kind of reaction took place?
  3. Why does this happen?
  4. Find out the molarity and volume used of silver nitrate and the mass of copper. What mass of silver should form?
  5. What is the value of the solid silver that was produced?
  6. What is the percent yield?