redox + chemistry + form 5

1. Half Equation and observation
Half equation Observation
Fe2+
 Fe3+
The green solution turns brown (yellow/brownish-yellow/brown depends on the
concentration of the solution).
Fe3+
 Fe2+
Brown solution turns green.
Cl2  Cl-
Yellow solution is turns colourless. (If gas is used: Greenish-yellow gas is
decolourized)
Br2  Br-
Brown bromine water turns colourless
(If bromine liquid is used: Brown bromine liquid is turns colourless)
Br-
 Br2 Colourless solution turns brown
I-
 I2 Colourless solution turns brown (yellow/brownish-yellow/ brown depends on the
concentration of solution).
MnO4
2-
Purple solution turns colourless
Cr2O7
2-
Orange solution turns green.
Cu  Cu2+
 Copper plate dissolves/corrodes/becomes thinner.
• Colourless solution turns blue/The intensity of the blue solution increases
Cu2+
 Cu  A brown solid is formed.
• The blue solution turns colourless / paler.
Metals other than copper
Zn  Zn2+
Mg  Mg2+
Zinc pieces or magnesium ribbon dissolves/corrodes/ becomes thinner.
Ag+
 Ag A shiny grey solid forms.
Type of reaction Note
Redox  Change of Fe2+
to Fe3+
/ Change of Fe3+
to Fe2+
 Displacement of metal from its salt solution
 Displacement of halogen from its halide solution
 Transfer of electron at a distance
 Reaction in electrolytic and chemical cells
 Rusting
 Extraction of metals
Non- redox
- oxidation numbers of
all elements are the
same
 Neutralisation
 Double decomposition
 Esterification
 Decomposition of carbonate salts
Oxidising agent Reducing agent
Chlorine water Potassium iodide , KI
Bromine water Potassium bromide , KBr
Acidified potassium manganate (VII) solution Reactive metals , Mg , Zn , Al
Acidified potassium dichromate (VI) solution Salt solution , Fe2+
Salt solution , Fe3+