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This is a chemistry study note based on the topic Oxidation and Reduction, you will learn everything you need to know about REDOX reactions
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The term REDOX is used by chemists as an abbreviation for the processes of oxidation and reduction which occur simultaneously. Oxidation and Reduction are two opposing but complementary processes. That is, no Oxidation process takes place without a corresponding Reduction and vice โ versa. DEFINITIONS OF OXIDATION AND REDUCTION REACTIONS I] OXIDATION AND REDUCTION IN TERMS OF OXYGEN a] OXIDATION: ๏ This is the addition of oxygen to a substance. OR It is the chemical process in which a substance gains oxygen. b] REDUCTION: ๏ This is the removal of oxygen from a substance. OR ๏ It is the chemical process in which a substance loses oxygen. c] OXIDIZING AGENT / OXIDIXER / OXIDANT: ๏ This is a substance that donates oxygen to another substance and so becomes reduced. OR ๏ This is any species that undergoes reduction in the course of interaction and so becomes reduced. d] REDUCING AGENT / REDUCER / REDUCTANT: ๏ This is a substance that accepts oxygen from the substance and so becomes oxidized. OR ๏ This is any species that undergoes oxidation in the course of interaction and so becomes oxidized. 2] OXIDATION AND REDUCTION IN TERMS OF HYDROGEN a] OXIDATION: ๏ This is the removal of hydrogen from a substance. OR ๏ It is the chemical process in which a substance loses hydrogen. b] REDUCTION: ๏ This is the addition of hydrogen to a substance. OR ๏ It is the chemical process in which a substance gains hydrogen. c] OXIDIZING AGENT / OXIDIXER / OXIDANT: ๏ This is a species that accepts hydrogen from a substance and so becomes reduced. OR ๏ This is any species that undergoes reduction in the course of interaction and so becomes reduced.
d] REDUCING AGENT / REDUCER / REDUCTANT: ๏ This is a species that donates hydrogen to another substance and so becomes oxidized. OR ๏ This is any species that undergoes oxidation in the course of interaction and so becomes oxidized. MODERN DEFINITIONS OF OXIDATION AND REDUCTION REACTIONS 1] OXIDATION AND REDUCTION IN TERMS OF ELECTRON TRANSFER This is the most concise definition of Oxidation and Reduction reaction. From electronic point of view: I] OXIDATION: ๏ This is a process involving loss of electron(s) by an atom or ion. ๏ The species that loses electrons is said to be oxidized. II] REDUCTION: ๏ This is a process involving gain of electron(s) by an atom or ion. ๏ The species that gains electron(s) is said to be reduced. [III]OXIDIZING AGENT/ OXIDANT/ OXIDIZER: This is any specie that accepts electrons and causes a co โ reactant to be oxidized in a redox reaction. IV] REDUCING AGENT/ REDUCTANT/ REDUCER This is any species that donates electrons and causes a co-reactant to be reduced in a redox reaction. OXDATION AND REDUCTION IN TERMS OF CHANGES IN OXIDATION NUMBER 1] OXIDATION: This is any chemical process in which there is an increase in oxidation number of a substance or an atom or an ion. The species whose oxidation number increases is said to be oxidized. II] REDUCTION This is any chemical process in which there is a decrease in oxidation number of a substance or an atom or an ion. The species whose oxidation number decreases is said to be reduced. III] OXIDIZING AGENT/OXIDANT/ OXIDIZER: This is the species whose oxidation number decreases in a REDOX reaction and has the potential to cause another substance to be oxidized.
A reducing agent can be identified by reacting one or more of reducing agents with oxidizing agents. SOME COMMON EXAMPLES OF REDUCING AGENTS. Hydrogen sulphide Ammonia Potassium iodide Sodium ethanediote, Na 2 C 2 O 4 Ethanedioic acid Conc. HCl Tin (ii) chloride Meatals in their free atomic forms Carbon Hydrogen Carbon (ii) oxide Any metal above hydrogen in activity series Iron (ii) salt eg FeSO 4 Na 2 S 2 O 3 Sulphur (iv) oxide TESTS FOR REDUCING AGENTS ๏ Add dilute H 2 SO 4 to a solution of the substance followed by a few drops of KMnO 4 solution and shake. The purple colour of KMnO 4 solution is discharged or decolourized [i.e changed to colourless]. This is because the purple MnO4-^ is reduced to colourless Mn2+^ ions. This indicates the presence of a R.A. ๏ Add dilute H 2 SO 4 to a solution of the substance followed by a few drops of K 2 Cr 2 O 7 solution and shake. The orange colour of K 2 Cr 2 O 7 solution changes to green. This is because the orange Cr 2 O 7 2-^ is reduced to green Cr3+. The test solution is therefore a R.A. ๏ Add a few drops of brown solution of Iron [III] chloride to a solution of the substance. The solution turns green. This indicates that the test solution is a R.A. ๏ Add a few of dilute HCl to the solid substance in a test tube. There is an effervescence of of a colourless gas that gives a โpopโ sound with a lighted splint. The gas is Hydrogen while the substance is a metal above hydrogen in the activity series. R.A is present. ๏ Mix the solid substance with black CuO and then heat. If the black CuO turns brown, then a R.A is present.
An oxidizing agent can be identified easily by the addition of a reducing agent to a solution containing an oxidizing agent. SOME COMMON EXAMPLES OF OXIDIZING AGENTS. Oxygen Conc. HNO 3 Hydrogen peroxide, H 2 O 2 Acidified tetraoxomanganate (VII), KMnO 4 Hot conc. H 2 SO 4 Acidified heptaoxodichromate (VI), K 2 Cr 2 O 7 Bromine Sodium chlorate (I), NaClO Chlorine Manganese (iv) oxide,MnO 2 Iodine Fluorine Ozone TESTS FOR OXIDIZING AGENTS ๏ H 2 S gas is bubbled / passed into a solution suspected to contain an O.A. A yellow deposit of sulphur shows that H 2 S been oxidized to Sulphur. This indicates the presence of an O.A. ๏ Heat the suspected substance with conc. HCl. The evolution of a greenish โ yellow gas with an irritating smell indicates the presence of an O.A ๏ Add a green solution of Iron (II) chloride to the test solution. The green solution turns brown. This is because Fe2+^ ion is oxidized to brown Fe3+^ ion. This indicates the presence of an O.A. ๏ Add dil. H 2 SO 4 to the test solution followed by iron (II) tetraoxosulphate (VI) solution. The green Fe2+^ ion changes to brown because Fe2+^ ion has been oxidized to Fe3+^ ion. This indicates the presence of O.A. ๏ Add dil. H 2 SO 4 to the solution of the sample followed by a few drops of potassium Iodide solution, KI and starch solution. If the starch solution turns blue โ black, then the solution is an O.A. ๏ Add dil. H 2 SO 4 to the solution of the substance followed by a few drops of potassium Iodide solution, KI and warm. If the solution turns brown, due to the evolution of iodine, then the solution is an O.A.