Chemical Reactions: Redox

Chemical Reactions: Redox

Redox Reactions

Definition

  • Redox reactions are ones in which both reduction and oxidation occur.
  • Oxidation is the loss of electrons while reduction is the gain of electrons.
  • The species that loses electrons is said to be oxidised, and the species that gains electrons is said to be reduced.

Oxidising and Reducing Agents

  • An oxidising agent is a substance that causes another substance to be oxidised, and it is itself reduced. In other words, it accepts electrons.
  • A reducing agent is a substance that causes another substance to be reduced, and it is itself oxidised. It donates electrons.
  • The oxidising and reducing agents in a redox reaction can be identified by changes in the oxidation state.

Oxidation States

  • Oxidation states indicate the degree of oxidation of an atom, by showing the number of electrons lost or gained.
  • An increase in oxidation state indicates oxidation, while a decrease indicates reduction.

Redox Equations

  • Half-equations show the oxidation or reduction of species in isolation, focusing on the transfer of electrons.
  • Both oxidations and reductions can be represented by half-equations.
  • For redox reactions in solutions, changes in oxidation states can be shown through ionic half-equations.

Redox in Everyday life

  • Redox reactions play a crucial role in many natural and industrial processes.
  • They’re essential in energy production, such as in batteries and fuel cells.
  • Redox reactions also occur in biological processes such as photosynthesis and respiration.
  • In the environment, they play a vital role in corrosion and the natural weathering of rocks.

Redox Titrations

  • Redox titrations can determine the concentration of an unknown solution by reacting it with a solution of known concentration.
  • The point at which all the reactants have precisely reacted is called the equivalence point, which is detected by a colour change.
  • An indicator can be used to highlight the end point of the titration, where the colour change occurs.

Balancing Redox equations

  • Balancing redox equations may require adding electrons, hydrogen ions (H+) or water (H2O) molecules to make sure the number of atoms is balanced on both sides.
  • In redox equations, charges must also be balanced on both sides.
  • It’s important to ensure that the total increase in oxidation state in the equation is equal to the total decrease. This validates the conservation of charge in redox reactions.