Electrochemistry Vocabulary/Electrochemical Cell
  • It is expected that students will understand the fundamental redox definitions and memory aids.
  • It is expected that students will be able to define, draw and label, and explain the operation of all aspects of an electrochemical cell.
  • It is expected that students will be able to write the 1/2 reactions and the net reaction for an electrochemical cell.

COOL School

Let's look at the foundational vocabulary and key memory aids for the electrochemistry unit. Let's also do a full analysis of a typical electrochemical cell.


1.0 Electrochemistry Definitions

1) Reduction A reaction involving electron gain.
2) Oxidation A reaction involving electron loss.
3) Redox An abbreviation for “reduction/oxidation”, which is synonymous with "electrochemistry".
4) Oxidizing agent The reactant species which causes another reactant species to be oxidized. The oxidizing agent itself will experience reduction.
5) Reducing agent The reactant species which causes another reactant species to be reduced. The reducing agent itself will experience oxidation.
6) Electrochemical cell A system of electrodes and electrolytes which allows a spontaneous chemical reaction which produces an electric current.
7) Electrolytic cell A system of electrodes and electrolytes which has an electric current forced through it to cause a non-spontaneous reaction to occur
8) Half cell One of the two beakers present in an electrochemical or electrolytic cell.
9) Half reaction That portion of the overall chemical reaction which happens in one of the two beakers present in an electrochemical or electrolytic cell.
10) Anion A negative ion.
11) Anode

The electrode which attracts the anion.
(ie.The positive electrode)
12) Cation A positive ion.
13) Cathode

The electrode which attracts the cation.
(ie.The negative electrode)
14) H2 reference cell. The Hydrogen half cell is arbitrarily chosen as the cell which all other cells are connected to when their standard voltage is measured. The Hydrogen half cell is assigned a voltage of 0.00 V

15) Standard reduction potential (E°)

The voltage produced by any half cell joined to the standard H2 half cell at standard conditions (ie. 25° C, standard state, 1.0 M solutions)
Memory Aid #1

LEO Loss of electrons is oxidation
the lion says  
GER Gain of electrons is reduction
Memory Aid #2

The ca-t-ion is the positive ion and the anion is the other ion (that is, the negative ion).

The cation is attracted to the cathode and the anion is attracted to the anode.

Therefore: cation +, and cathode -

               anion -, and anode +
Memory Aid #3
Think vowels to associate:
  • Oxidation.
  • Increase in oxidation number.
  • Anode is where this occurs.
Think consonants to associate:
  • Reduction.
  • Decrease in oxidation number.
  • Cathode is where this occurs.

2.0 The Electrochemical Cell

Here are three animations of an electrochemical cell

1. A time lapse, macroscopic illustration.

2. Events as they occur at the atomic and ionic level

3. "Drag and drop" to name the parts of the cell.

Use two half cells, a salt bridge and an electrical wire to produce electricity by chemical action. In this arrangement, Zn(s) is in contact with Zn+2(aq) in the left beaker while Cu(s) is in contact with Cu+2(aq) in the right beaker. The two electrodes are in electrical contact with each other through the wire and the two solutions can remain electrically neutral by ion migration as needed through the salt bridge. This allows the ion able to pull electrons toward itself more forcefully, to do so, while the opposite metal atoms will be forced to relinquish an equal number of electrons to the wire as these atoms become ions and enter the solution. The ion, which took two electrons, becomes an atom and builds a coating of more metal atoms on its electrode. The standard reduction potential table (E° table) tells us which ion is able to pull electrons toward itself more forcefully. This is always the ion which is higher on the left side of the table. This ion's half reaction will proceed from left to right (ie. reduction), while the metal which loses two electrons will have its half reaction occurring in reverse (ie. oxidation).

The two half reactions and the net reaction are:

Cu+2(aq) + 2e- Cu(s)    
    Zn(s) Zn+2(aq) + 2e-
Cu+2(aq)   Zn(s) Zn+2(aq) + Cu(s)

Note that the spectator NO3- ions are not shown.

Also note that the summation reaction is called the net reaction.

Examples

Example 1: Solve the question in your notebook then check your solution.

An electrochemical cell is set up with a Cobalt electrode in a solution of Cobalt Nitrate in the first beaker and a Zinc electrode in a solution of Zinc Nitrate in the second beaker. The electrodes are connected with a wire and a salt bridge is used to connect the two beakers.

  • Write the two half reactions and the net reaction.

  • Identify the anode.

  • Identify the cathode.

  • Identify the species reduced.

  • Identify the species oxidized.

Example 2: Solve the question in your notebook then check your solution.

An electrochemical cell is set up with an Aluminum electrode in a solution of Aluminum Nitrate in the first beaker and a Zinc electrode in a solution of Zinc Nitrate in the second beaker. The electrodes are connected with a wire and a salt bridge is used to connect the two beakers.

  • Write the two half reactions and the net reaction.

  • Identify the anode.

  • Identify the cathode.

  • Identify the species reduced.

  • Identify the species oxidized.

Activities

In your Textbook read pgs 189 - 192, 215 - 217 and answer any questions.

Supplementary Worksheet:

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