The term oxidation was first used to describe reactions in which oxygen combined with an element or a compound to form another substance. Nowadays, we say that a substance is oxidised if it gains oxygen, loses hydrogen, loses electrons or increases its oxidation state after a reaction. In this video we will learn almost everything about redox reactions and oxidation state covered in O level syllabus.
▧▧ TOPIC COVERED ▧▧
❖ Definition of oxidation reduction
❖ Oxidation number
❖ Laws of oxidation number
❖ Identifying oxidation state of element from a compound or ion
❖ Relation of oxidation state with redox reactions
❖ Deducing oxidising and reducing agent
▧▧ Relevant Past Paper Questions ▧▧
June, 2018※ A redox reaction happens when chlorine gas is bubbled through aqueous potassium iodide.
Cl2(g) + 2I-(aq) → I2(aq) + 2Cl-(aq)
(i) Describe what is observed during this reaction.[1]
(ii) Use the equation to explain that oxidation takes place in this reaction. [1]
(iii) Use the equation to explain that reduction takes place in this reaction. [1]
November, 2015※Copper is oxidised by concentrated sulfuric acid. This redox reaction can be represented by equations A and B.
A Cu → Cu2+ + 2e–
B 4H+ + SO42– + 2e– → 2H2O + SO2
Which reaction, A or B, is oxidation and which is reduction? Explain your answer. [2]
June, 2008※In which oxide does X have the same oxidation state as in the chloride, XCl3?
A X3O B X2O C XO2 D X2O3
Quiz for practice from this video: https://quizizz.com/join/quiz/6079efda2dd282001b5a09ef/start
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