Displacement reactions :
Reactions of chlorine, bromine, and iodine with potassium chloride, potassium
bromide and potassium iodide.
In these reactions we determine which of the halogens chlorine, bromine or iodine is the
strongest.
Potassium iodide + chlorine gas
In this reaction when potassium iodide solution
is put into chlorine gas:
a rapid reaction occurs.
black iodine solid is formed along with
potassium chloride solution.
The chlorine has kicked the iodide out.
CHLORINE is stronger than IODINE
The equation for the reaction is:
potassium +
chlorine
iodide
gas
2KI
+
Cl2
potassium
chloride
2KCl
+
iodine
+
I2
Potassium bromide + chlorine gas
In this reaction when potassium bromide
solution is put into chlorine gas
a rapid reaction occurs
brown bromine liquid is formed along with
potassium chloride solution.
The chlorine has kicked the bromide out.
CHLORINE is stronger than BROMINE
The equation for the reaction is:
potassium +
chlorine
bromide
gas
2KBr
+
Cl2
potassium
chloride
2KCl
+
bromine
+
I2
Potassium chloride + chlorine gas
In this reaction when potassium chloride
solution is put into chlorine gas –
No reaction occurs.
CHLORINE and CHLORIDE are of equal STRENGTH - hence no reaction
Potassium iodide + bromine liquid
In this reaction when potassium iodide solution
is put into bromine liquid :
a rapid reaction occurs
black iodine solid is formed along with
potassium bromide solution.
The bromine has kicked the iodide out.
BROMINE is stronger than IODINE
The equation for the reaction is:
potassium
iodide
2KI
+
bromine
vapour
+
Br2
potassium
bromide
2KBr
+
iodine
+
I2
From these findings the order of reactivity is (STRONGEST FIRST)
CHLORINE > BROMINE > IODINE