Sciences - Co-ordinated (Double) - 0654 CIE

Redox

Gbogbo ọrọ náà

When iron rusts, when a fuel burns, when a battery drives your phone, the same hidden bargain is taking place: one substance loses something and another gains it. That bargain is a redox reaction, the simultaneous oxidation and reduction that powers an enormous slice of chemistry, biology and industry.

In this lesson you will learn redox three ways: as the gain and loss of oxygen, as the transfer of electrons, and as a change in oxidation number. You will assign oxidation numbers with Roman numerals, spot oxidising and reducing agents, and read the tell-tale colour changes that prove a redox reaction has happened.

Ebumnobi

Use a Roman numeral to indicate the oxidation number of an element in a compound.
Define redox reactions as involving simultaneous oxidation and reduction.
Define oxidation as gain of oxygen and reduction as loss of oxygen.
Identify redox reactions as reactions involving gain and loss of oxygen.
Identify oxidation and reduction in redox reactions.
[Supplement] Define oxidation in terms of: (a) loss of electrons (b) an increase in oxidation number.
[Supplement] Define reduction in terms of: (a) gain of electrons (b) a decrease in oxidation number.
[Supplement] Identify redox reactions as reactions involving gain and loss of electrons.
[Supplement] Identify redox reactions by changes in oxidation number using: (a) the oxidation number of elements in their uncombined state is zero (b) the oxidation number of a monatomic ion is the same as the charge on the ion (c) the sum of the oxidation numbers in a compound is zero (d) the sum of the oxidation numbers in an ion is equal to the charge on the ion.
[Supplement] Identify redox reactions by the colour changes involved when using acidified aqueous potassium manganate(VII) or aqueous potassium iodide.
[Supplement] Define an oxidising agent as a substance that oxidises another substance and is itself reduced.
[Supplement] Define a reducing agent as a substance that reduces another substance and is itself oxidised.
[Supplement] Identify oxidising agents and reducing agents in redox reactions.

Akọmọ Ojú-ẹkọ

Redox reactions are the engine room of chemistry. Combustion, respiration, rusting, the extraction of metals from their ores and every battery and fuel cell all rely on electrons moving from one substance to another. Learn to recognise oxidation and reduction reliably and a huge amount of chemistry suddenly fits one pattern.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Redox. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Which statement defines oxidation in terms of electrons? A. Gain of electrons B. Loss of electrons C. Gain of protons D. Loss of neutrons Answer: B
What is the oxidation number of an element in its uncombined state? A. +1 B. -1 C. 0 D. equal to its group number Answer: C
In the reaction CuO + H2 -> Cu + H2O, the reducing agent is: A. CuO B. H2 C. Cu D. H2O Answer: B
An oxidising agent is a substance that: A. is itself oxidised B. oxidises another substance and is itself reduced C. loses oxygen only D. gains electrons from no other species Answer: B
When iodide ions turn acidified potassium iodide from colourless to yellow-brown, the iodide ions are: A. reduced B. oxidised C. unchanged D. acting as an oxidising agent Answer: B