Ionic Half-Equations

“Ionic Half-Equations”:

• Ionic half-equations demonstrate either reduction or oxidation, but not both simultaneously. They are considered ‘half’ because they only depict one part of the entire redox process.
• These equations are essential in evaluating how electrons are transferred in redox reactions.
• In a reduction half-equation, electrons are on the left-hand side, signifying a gain of electrons. An increase in the number of electrons implies a reduction.
• In an oxidation half-equation, electrons are on the right-hand side, indicating a loss of electrons. A decrease in the number of electrons signifies oxidation.
• It’s crucial to note that the total charge on each side of the half-equation must be equal. To achieve this, you may need to add ions to balance the charges.
• For half-equations including atoms other than hydrogen and oxygen, first balance the atom in question, then balance oxygen atoms by adding water (H2O), hydrogen atoms by adding hydrogen ions (H+) and finally, balance charges by adding electrons (e-).
• Ionic half-equation in acidic conditions, balance H+ ions with water and in basic conditions, balance OH- ions with water.
• The balanced half-equations can be combined to provide the overall equation for the redox reaction.
• When adding half-equations together, make sure that the number of electrons is the same in both half-equations. If they aren’t, multiply the entire half-equation by a factor that will ensure the electrons balance.
• Be careful to note the state symbols (s, l, g, aq) of the substances. These indicate whether the substance is solid, liquid, gaseous, or aqueous.
• Practice writing ionic half-equations frequently as they are fundamental to understanding the concept of redox reactions. The skill to draught and balance them is crucial and must be mastered.