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Description
This cassette is intended to teach the basic concepts of electrochemical cells. starting with the question of how chemical reactions can be used to provide electricity we look at the displacement o...f silver from solution by copper. This reaction can be seen to consist of two halves, the oxidation of copper to copper ions with liberation of electrons, and the use of these electrons to reduce silver ions to silver. This introduces the idea of half cell reactions and the possibility of separating the two reactions. However, when the two reactions are connected through an external circuit, no potential results. a salt bridge demonstrates the need for an internal electrical connection between the half cells. With a working Cu/Cu2+, Ag/Ag+ cell, using a membrane in place of the salt bridge, we examine the changes that take place as the cell is allowed to 'run down' through the external circuit to a true chemical equilibrium. The observations are interpreted at various stages using animations. A break in the cassette allows for a discussion of this first sequence before going on to the final sequence which uses a similar apparatus to examine anH2/H+, Ag/Ag+ cell. A major point of this second demonstration is to show how by greatly lowering the silver ion concentration the direction of the cell reaction is reversed, such that oxidation takes place at the silver electrode and reduction at the hydrogen electrode. This demonstration can then be used as a basis for discussing the link between E and dG/d - and the form of the Nernst equation.
This cassette is intended to teach the basic concepts of electrochemical cells. starting with the question of how chemical reactions can be used to provide electricity we look at the displacement o...f silver from solution by copper. This reaction can be seen to consist of two halves, the oxidation of copper to copper ions with liberation of electrons, and the use of these electrons to reduce silver ions to silver. This introduces the idea of half cell reactions and the possibility of separating the two reactions. However, when the two reactions are connected through an external circuit, no potential results. a salt bridge demonstrates the need for an internal electrical connection between the half cells. With a working Cu/Cu2+, Ag/Ag+ cell, using a membrane in place of the salt bridge, we examine the changes that take place as the cell is allowed to 'run down' through the external circuit to a true chemical equilibrium. The observations are interpreted at various stages using animations. A break in the cassette allows for a discussion of this first sequence before going on to the final sequence which uses a similar apparatus to examine anH2/H+, Ag/Ag+ cell. A major point of this second demonstration is to show how by greatly lowering the silver ion concentration the direction of the cell reaction is reversed, such that oxidation takes place at the silver electrode and reduction at the hydrogen electrode. This demonstration can then be used as a basis for discussing the link between E and dG/d - and the form of the Nernst equation.
| Module code and title: | S342, Physical chemistry: principles of chemical change |
|---|---|
| Item code: | S342; SS |
| Published: | 1985 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:25:00 |
| + Show more... | |
| Producer: | Barrie Whatley |
| Contributor: | Kiki Warr |
| Publisher: | BBC Open University |
| Keyword(s): | Anion; Anode; Cathode; Cation; Half cell; Hydrogen electrode; pH; Reaction; Salt bridge |
| Subject terms: | Electrochemistry |
| Master spool number: | HOU4587 |
| Production number: | FOUS291S |
| Videofinder number: | 2032 |
| Available to public: | no |
