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.
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.
