Transcript Redox – Level 3 Introduction / Revision

Redox – Level 3
Introduction / Revision
Review of Keywords
Identifying Redox Reactions
Common Oxidants
Common Reductants
Author: J R Reid
Keywords
Oxidation – a chemical reaction which results in
the loss of electrons from a chemical species
Reduction – a chemical reaction which results in a
chemical species gaining electrons
Oxidant – a chemical species that has the ability to
take electrons from other chemicals – i.e. it causes
oxidation
Reductant – a chemical species that has the ability
to give electrons to another species – i.e. it causes
reduction
Electrolysis – the process by which ionic
compounds are split into their atoms using electric
currents
Identifying Redox Reactions
A redox reaction must result in the
movement of electrons from one element
to another.
To identify whether this is happening we
must prove that one element is changing
it’s oxidation number (see Level 2 notes:
Redox – Oxidation numbers)
For example:
SO2 → SO3
Oxidation Number = +4
Oxidation Number = +6
Therefore, an oxidation number change has occurred
Common Oxidants
Oxygen:
O2 + 4e- → 2O2Permanganate: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
Dichromate:
Cr2O72- + 14H+ +6e- → 2Cr3+ + 7H2O
Iron(III) ion:
Fe3+ + e- → Fe2+
Halogens:
X2 + 2e- → 2XHydrogen peroxide: H2O2 + 2H+ + 2e- → 2H2O
Iodate:
IO3- + 6H+ + 6e- → I- + 3H2O
Bromate:
BrO3- + 6H+ + 6e- → Br- + 3H2O
Common Reductants
Hydrogen:
H2 → 2H+ + 2eThiosulfate: 2S2O32- → S4O62- + 2eIron(II) ion: Fe2+ → Fe3+ + eHalides (Halogen ions): 2X- → X2 + 2eZinc:
Zn → Zn2+ + 2eOxalate:
C2O42- → 2CO2 + 2eSulfur dioxide:SO2 + 2H2O→ SO42- + 4H+ + 2e-
Physical Characteristics of
Reductants- match the rows
MnO2
I-
Colourless gas
Colourless gas
BrClSO2
Brown gas
Colourless ion
Colourless ion
Fe2+
H2
NO2
C2H42-
Colourless ion
Colourless ion
Colourless ion
Pale green ion
S2O32-
Brown solid
Physical Characteristics of
Oxidants - match the rows
MnO4I2
Brown solution
Brown/red liquid
Br2
Cl2
BrO3IO3-
Green gas
Colourless ion
Colourless ion
Colourless liquid
Fe3+
Cu2+
Cr2O72-
Blue ion
Orange ion
Orange/brown
ion
Purple ion
H 2O 2
Revision
From level 2 Redox you are expected
to also know:
How to balance half equations
How to combine half equations
What electrolysis is (with some examples)
See level 2 notes for details