1.07 Oxidation, Reduction and Redox
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What is oxidation ?
• The loss of electrons • Gaining of oxygen • Loss of hydrogen.
What is reduction ?
• The gaining of electrons • The loss of oxygen • The gaining of hydrogen.
What is an oxidising agent ?
Substance that gains electrons (reduction), other species gets oxidised.
What is a reducing agent ?
Substance that loses electrons (oxidised), other species gets reduced.
What are the half equations and ionic equation for the following reaction: SnO + Zn -> ZnO + Sn
• Sn2+ + 2e- -> Sn • Zn -> Zn2+ + 2e- • Sn2+ + Zn -> Sn + Zn2+ .
Define oxidation state
A number which represents the number of electrons lost or gained by an element in a compound
What is the oxidation state of oxygen in OF2 ?
• O = +2 • In most other compounds it will be -2
What is the oxidation state of hydrogen in KH ?
• H = -1 • Hydrogen is usually +1 in most other compounds.
What is the oxidation state of chlorine in NaClO ?
• Cl = +1 • Cl is usually -1, NaClO is formed in a disproportionation reaction.
Define the term disproportionation
Occurs when in a redox reaction the oxidation state of atoms of the same element increases for some atoms but decreases for others
What is the oxidation state of phosphorus in PCl5 ?
P = +5
What is the oxidation state of nitrogen in ammonia ?
N = -3
What is the oxidation state of arsenic in AsO4 3-
As = +5
What is the oxidation state of iron in K4Fe(CN)6 ?
Fe = +2
Why is
What happens in a redox reaction ?
• Electrons are transferred from one species to another • One species is oxidised and another reduced.
Why is the following reaction not a redox reaction ? : 2CrO4 2- + 2H+ -> Cr2O7 2- + H2O
No element is reduced or oxidised