Redox Reactions

Oxidation Numbers

• Oxidation numbers, also known as oxidation states, are used to track electron transfer in chemical reactions.
• The overall charge of a neutral compound is zero.
• The oxidation number of an atom in its elemental form is zero. Examples include O2, Na, and H2.

Identifying Redox Reactions

• A redox reaction involves both reduction and oxidation processes.
• If the oxidation number of a substance increases, it is oxidized. The substance loses electrons.
• If the oxidation number of a substance decreases, it is reduced. The substance gains electrons.
• If the oxidation number of an element does not change during a reaction, it is neither oxidized nor reduced.

Oxidation

• Oxidation is the process where a substance loses electrons, resulting in an increase in its oxidation number.
• A substance being oxidized is a reducing agent because it causes another substance to be reduced.

Reduction

• Reduction is the process where a substance gains electrons, resulting in a decrease in its oxidation number.
• A substance being reduced is an oxidizing agent because it causes another substance to be oxidized.

Activity Series of Metals

• Metals higher in the activity series are more easily oxidized.
• Metals lower in the activity series are more easily reduced.
• The metal that needs to be oxidized must be higher in the series than the metal being reduced.
• The reading on a voltmeter will be lower than 2. 3, but higher than z jY.

Examples and Equations

• Example: Cl is reduced, and something else (Mnt) is oxidized. Mnt Mnt gains 11 t I 1
• 2H^+ + 2e^- \rightarrow H2 is an example of reduction. H2 is being reduced.
• Oxidation number: 2H^+ \text{is reduced to } H_2
• The total number of electrons lost must equal the total number of electrons gained in all redox reactions.
• Number of electrons lost = Number of electrons gained.
• Number of electrons for element oxidized = number of electrons for element reduced.

Atom Examples

• Is an atom present? Examples: 0, 2, 1, 2