Electricity and Chemistry

Electricity in Chemical Reactions

Electrolysis is the process of breaking down ions by electrical energy, usually in molten or solution state.
Positive ions, or cations, move to the cathode (negative electrode) and gain electrons in a reduction process.
Negative ions, or anions, migrate to the anode (positive electrode) and lose electrons in an oxidation process.
Electrolyte is the compound that conducts electricity in molten or solution state and is split in the process.
Electrolysis enables the extraction of reactive metals like aluminium and sodium from their ores.

Products of electrolysis depend on the electrolyte and the concentrations of ions present.
At the cathode, hydrogen is usually discharged if the ions are from acids. Other metals may be discharged if they are less reactive than hydrogen.
At the anode, oxygen is typically discharged if the electrolyte is a salt. If the electrolyte is a halide, then a halogen will be discharged.

A Redox reaction involves both reduction (gain of electrons) and oxidation (loss of electrons).
Oxidation state or oxidation number indicates the total number of electrons that an atom either loses or gains in order to form a chemical bond with another atom.
Substances that can both oxidise and reduce are called Redox agents.

Exothermic reactions release heat energy to the surroundings. Combustion reactions and neutralisation reactions are exothermic.
Endothermic reactions absorb heat energy from the surroundings. Thermal decompositions are examples of these reactions.
Energy diagrams can be used to represent the energy changes during a chemical reaction. The difference between the energy levels of the reactants and the products refers to the enthalpy change.

The rate of reaction depends on the temperature, concentration, pressure, surface area, and presence of catalysts.
The Collision Theory states that the rate of reaction depends on the frequency of effective collisions between reactant particles.
A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy.