Redox Reactions

Redox reactions involve the transfer of one or more electrons to or from the transition metal ion.

A good example is the gradual reduction of manganate (VII) ions, MnO₄^-.

MnO₄- > MnO₄^2- > MnO₂ > Mn²⁺

The manganese is successively reduced from oxidation state 7 to 6,4,2.

You should know the colours for all of these and the many other reduction sequences.

Sometimes it is easier to show what is being oxidised and reduced by writing half equations.

A single half-equation will show ONLY reduction or ONLY oxidation, never both in the same equation.

The equation must be balanced both in terms of atoms and charge.

Two half-equations can be put together to create the overall Redox Equation, but the electrons must be balanced.

Cu²⁺(aq) + 2e-→ Cu(s)                               reduction

                                                                             +

Zn(s) → Zn²⁺(aq) + 2e-                              oxidation

                                                                           =

Cu²⁺(aq) + Zn(s)→Cu(s) + Zn²⁺(aq)      redox equation