Unit 3 - Electrochemical Cells Flashcards
Galvanic Cell
A galvanic cell is a type of electrochemical cell in which chemical energy is converted into electrical energy. (E.g cells in mobile)
Several cells connected series-higher potentential difference-battery
External Circuit in a Galvanic Cell
When the chemical reaction produces a current that flows through set up wires to another external equipment, it is called an external circuit
Galavnometer in Galvanic Cell
If you replace the light in a Daniell Cell with a galvanometer, it will indicate the electron flow between the two electrodes
Salt bridge in Galvanic Cell
A salt bridge is often made from filter paper soaked in a relatively unreactive electrolyte, such as a solution of potassium nitrate
Energy Tranformations in Direct Reactions
Chemical energy in a direct reaction, where the elctrode is placed directly into an electrode liquid, is turned into thermal energy. It is a spontaneous exothermic reaction with a displacement equation
Gas in half-cells
Gas electrodes are kept in the solution with a tube over the top and contains other species not involved in the reaction such as spectator ions and the solvent
Purpose of the salt bridge
The salt bridge contains ions that are free to move so that they can balance the charges formed in thr two half-cell components
Cations and Anions
Cations move towards the cathode (+) while anions move towards the anode (-). Negative charge would be accumulated in the anode solution and positive charge in the cathode if a salt bridge was not present.
Potential Difference
A current flows in a galvanic cell because one half-cell has a greater tendency to push electrons into the external circuit. Chemists say that a potential difference exists between the two half-cells
Standard Electrode Potential
A standard electrode potential can be assigned to each half cell from the data booklet.
Standard conditions: pressure of 1 bar, 1mol concentation
Electrochemical Series
In the data booklet
Can be used as the elements higher up are more likely to complete a reduction reaction
Electrolytic Cells
During electrolysis, reactions occur at the surface of both electrodes.
The electrical required for these reactions to occur is provided by the power supply.
The power supply can be regarded as a type of ‘electon pump’ withdrawing electrons through the external circuit from the positive electrode (anode) and pushing them onto negative electrode (Cathode)
Electrode pieces are unreactive
Electrolytic Cells #2
The overall reaction that occurs is non - spontaneous, a reaction that would not occur naturally and involves the consumption of electrical energy to produce chemical energy
Electolytic Cells #3
The conducting liquid in an electrolytic cell is called the electrolyte, and can either be molten ionic salt, such as NaCl (l) or a solution of an ionic solid , such as NaCl (aq). It acts similar to the salt bridge in a galvanic cell.
Redox in an Electrolytic cell
Oxidation occurs at the anode (+)
Reduction occurs at the cathode (-)
Reactive electrodes cause one material to deposit on the other
