Electrolysis Part 1 Active Learning Instructional Activity

This instructional activity serves as a guide for students using the Greenbowe, Abraham & Gelder electrolysis computer simulation. An instructional activity enabling students to explore a Cu-Cu electrolysis cell and a Zn-Cu electrolysis cell.

Curriculum Notes 

Student Difficulties (Misconceptions) with Electrolysis Addressed in this Activity

1. Not understanding the "+" and "-" signs on a battery or Direct Current Power Source.  At the "-" terminal electrons are pushed out of the battery. At the "+" terminal electrons are pulled into the battery.

2. In electrolytic cells, oxidation occurs at the cathode and reduction occurs at the anode.

3. When predicting an electrolytic reaction, the half-cell reactions are reversed prior to combining them.

4. When identical electrodes are used in an electrolysis experiment, the same reaction occurs at both electrodes and the products are the same at both electrodes.

5. Electrons move through electrolytes by being attracted to positive ions in the solution.

6. Representing an electrolysis process using three levels of representation.  Relating what occurs at the macroscopic level to what occurs at the particle level, to the symbolic level (chemical equations).

Learning Objectives

1.  Given a diagram of an electrolytic cell, identify the anode, cathode, direction of which electrons and ions move, the location of the oxidation half-reaction, the location of the reduction half reaction.

2.  Given a description or a diagram of an electrolytic cell, write the oxidation half-reaction and the reduction half-reaction.

3.  Relate the amount of product(s) generated in an electrolytic cell to the stoichiometry of the reduction half-reaction and to the amount of electrical charge passed in the cell.

4.  At the particle level of representation (atom level), show how the number of electrons involved in a single reduction half-reaction, i.e. Zn2+ + 2e-> Zn, scales up to the mole level: i.e. 1 mole Zn2+ 2 mole e-> one mole Zn.

5. Calculate the quantity of of charged passed in an electrolytic cell, given the stoichiometry, and the amount of electrical current passed in a specific time in the cell.

6.  Calculate the mass of product produced during electrolysis given the stoichiometry, the amount of electrical current passed in a specific time in the cell.

7.  Determine the relationship among coulombs, faradays, time, and reduction-half reaction for an electrolysis cell.

AP Chem Learning Objectives  The student can

LO 3.12:  make qualitative or quantitative predictions about electrolytic cells based on half-cell reactions and potentials and/or Faraday's laws.

LO 3.13:  analyze data regarding electrolytic cells to identify properties of the underlying REDOX reactions.

LO 5.15 is able to explain how the application of an external energy source (power source) can be used to cause processes that are not thermodynamically favorable to become more favorable (i.e. to occur).

Pre-Requisite Knowledge

1.  Oxidation-reduction reaction reactions involving a transfer of electrons.

2. Galvanic cells.

3.  Physics: voltage and current; the function of Direct Current (DC) power supplies; how batteries push electrons in a circuit

Footnotes 

References

Gelder, J.I., Abraham, M.R., Greenbowe, T.J.  (2015).  “Teaching electrolysis with guided-inquiry.”  In Sputnik to Smartphones: A Half-Century of Chemistry Education, M. Orna (ed.) ACS Symposium Series, Volume 1208, pp 141-154. American Chemical Society, Washington, D.C.

 

© Copyright 2012 Email: Randy Sullivan, University of Oregon Chemistry Department and UO Libraries Interactive Media Group