Electrochemistry

Oxidation

The process in which a substance loses electrons or gains oxygen.

Reduction

The process in which a substance gains electrons or loses oxygen.

Gain of oxygen

An increase in the number of oxygen atoms in a compound.

Loss of oxygen

A decrease in the number of oxygen atoms in a compound.

Loss of electrons

When a substance loses electrons during a reaction.

Gain of electrons

When a substance gains electrons during a reaction.

Loss of hydrogen

A decrease in the number of hydrogen atoms in a compound.

Gain of hydrogen

An increase in the number of hydrogen atoms in a compound.

Increase in oxidation number

A rise in the oxidation state of an element in a compound.

Decrease in oxidation number

A decrease in the oxidation state of an element in a compound.

Electrolytic Cell

A cell where the electrodes can be placed in a single compartment with an electrolyte, driven by an external battery source.

Anode and Cathode

In an electrolytic cell, the anode is where oxidation occurs and becomes the positive terminal, while the cathode is where reduction occurs and becomes the negative terminal.

Electrolysis

The process of using an electric current to induce a chemical change, such as decomposing compounds like water or sodium chloride.

Brine

A solution of sodium chloride and water, used in the electrolysis process to produce chlorine, sodium hydroxide, and hydrogen.

Standard Cell Potential

The voltage generated by an electrochemical cell under standard conditions, calculated as the potential difference between two half cells.

Salt Bridge

A connection between two half cells in an electrochemical cell that allows ion movement to maintain ionic balance.

Standard Hydrogen Electrode

A reference electrode used to measure electrode potentials, with hydrogen gas bubbled into a solution and connected to a piece of platinum.

Standard Reduction Potential

The potential of a half-cell compared to the standard hydrogen electrode, indicating the tendency of a species to gain electrons.

Cell Diagram

A shorthand notation representing the anode and cathode reactions in an electrochemical cell, separated by double vertical lines.

Feasibility of a Reaction

Determined by calculating the standard cell potential from standard electrode potentials of two half cells; a positive value indicates a feasible reaction.

Spontaneity

The tendency of a reaction to occur without external intervention.

Feasible reaction

A reaction that is likely to occur based on the comparison of standard electrode potentials.

Zn + Cu2+ → Cu + Zn2+

A spontaneous reaction where zinc displaces copper from its solution.

E◦cell = E◦red - E◦ox

The formula to calculate the standard cell potential of a redox reaction.

Chlorine oxidation

The process of chlorine causing the oxidation of Fe2+ ions to Fe3+ ions.

Fe2+ + ½ Cl2 ↔ Cl- + Fe3+

The more feasible reaction where Fe2+ reacts with chlorine to form Fe3+ and chloride ions.

Aqueous iodine oxidation

The process of iodine causing the oxidation of silver to Ag+ ions.

2I- + Ag+ ↔ I2 + Ag

The feasible reaction where iodide ions react with silver ions to form iodine and silver.