CHEMICAL CHANGE: ELECTROCHEMICAL REACTIONS Flashcards
Galvanic cell
A cell in which chemical energy is converted into electrical energy. A galvanic (voltaic) cell has self-sustaining electrode reactions.
Electrolytic cell
A cell in which electrical energy is converted into chemical energy.
Redox reaction
A reaction in which an electron transfer takes place.
Oxidation
A loss of electrons./An increase in oxidation number.
Reduction
A gain of electrons./A decrease in oxidation number.
Oxidising agent
A substance that is reduced/gains electrons/whose oxidation number decreases.
Reducing agent
A substance that is oxidised/loses electrons/whose oxidation number increases.
Anode
The electrode where oxidation takes place.
Cathode
The electrode where reduction takes place.
Electrolyte
A solution that conducts electricity through the movement of ions.
Electrolysis
The chemical process in which electrical energy is converted to chemical energy OR the use of electrical energy to produce a chemical change.
Salt bridge
The connection between two half-cells needed to ensure electrical neutrality in the cell. OR A component used in a galvanic cell to complete the circuit.
Electrodes
An electrical conductor used in a galvanic cell to make contact with a nonmetallic part of the circuit e.g. the electrolyte.
Cell notation
A short way to represent a galvanic cell. When writing cell notation, the following convention should be used:
*The H2|H+ half-cell is treated just like any other half-cell.
*Cell terminals (electrodes) are written on the outside of the cell notation.
*Active electrodes: reducing agent | oxidised species || oxidising agent | reduced species
*Inert electrodes (usually Pt or C):
Pt | reducing agent | oxidised species || oxidising agent | reduced species | Pt Example: Pt | Cℓ-(aq) |Cℓ2(g) || F2(g) | F-(aq) | Pt
Overall cell reaction
The reaction obtained by combining two half-reactions.
Positive value of the standard emf
The reaction is spontaneous under standard conditions.
Standard conditions for a galvanic cell
Temperature: 25 °C / 298 K Concentration:
1 mol∙dm-3 Pressure (gases only):
101,3 kPa / 1 atmosphere
Standard hydrogen electrode
The reference electrode used to compile the Table of Standard Reduction Potentials.
The hydrogen half-cell was given a standard reduction potential of 0 V.
Half-cell notation:
Pt | H2(g) | H+(aq) Half-reaction: 2H+ + 2e- ⇌ H2
Electroplating
The covering of an object with a metal by making it the cathode in an electrolytic cell.
Bauxite
The ore from which aluminium is recovered.
Cryolite
An aluminium compound in which aluminium oxide is dissolved to reduce the cost of the extraction of aluminium. Cryolite has a lower melting point than aluminium oxide.
