These notes offer a comprehensive guide to the theory needed to write final exams in matric. They contain all the information on Redox and Galvanic Cells in the IEB chemistry syllabus. They are typed in a column format for easy learning. They have an array of diagrams to aid learners in their physi...
Oxidation and Reduction
Chapter 17
Electrochemistry: refers 2 chemical Oxidation Numbers
reactions where converted from
Indicates if electrons move away /
chemical energy 2 electrical energy /
towards atom during bond formation.
electrical energy 2 chemical energy.
Pos moves away & neg moves towards.
Basics Rules
Redox reactions occur when electron 1. Pure element = 0
transfer takes place. 2. Hydrogen = +1 unless it is a
Represented by 2 half reactions & hydride of an alkaline metal (group
both must occur. 1&2) = -1
• An oxidation half reaction 3. Oxygen = -2 except when bonded 2
• A reduction half reaction fluorine = +1, if a peroxide = -1
• both halves are added 2 4. Group 1,2&3 = positive &
produce net redox reaction. correspond w/ group number
Oxidation 5. Zinc(Zn) = +2 & silver(Ag) = +1
6. Halides (neg ions of halogens) = -1
(OIL) unless bonded 2 oxygen = +1
Loss of electrons by a substance 7. Sum of oxidation numbers add up
(atom, molecule, ion). to 0
𝑋 → 𝑋+ + 𝑒− 8. Sum of compound ions add up to
Electrons = product. the charge of the ion
𝑌− → 𝑌 + 𝑒− Example
Substance that = oxidised (loses 𝑀𝑛𝑂4 − : find oxidation # of Mn.
electrons) = reducing agent (RA). 𝓍 + 4 −2 = −1
Oxidation # of substance oxidized 𝓍 = +7
increases (less neg/+ pos)
SAGS DEFINITIONS
Reduction
(RIG) Redox a reaction involving
reaction the transfer of
Gain of electrons (in atom, molecule, electrons
ion)
𝑋 + 𝑒− → 𝑋− Oxidation the loss of electrons
𝑌+ + 𝑒− → 𝑌
Reduction the gain of electrons
Electrons = reactant.
Substance = reduced is oxidising agent oxidising a substance that
(OA). agent accepts electrons
Oxidation # of substance that is
reduced decreases. reducing a substance that
agent donates electrons
, Electromotive Series
Electromotive series (reactivity series) = list of subs which are arranged in
order of ability 2 act as RA/OA.
The Table of Standard Reduction Potentials = an electromotive series.
Before table can be used, all ionic compounds & H2SO4, HNO3 as well as HCℓ
must be dissociated in2 ions.
Strong reducing
Oxidation half- agents = higher
reactions = read on table & are
from right 2 oxidised.
left.
Reduction half-
reactions = read
from left 2
right.
*Always use
single arrows.*
Strong oxidising
agents = lower
on table & are
reduced.
Substances on Substances on
left = reduced & right = oxidised &
are OA. are RA.
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