potassium bromide + iodine.Br2(g) + 2KI(aq)
2KBr(aq) +
I2(s)gcsescience.com 27 gcsescience.com
The Halogens - Displacement Reactions.
What are Displacement Reactions?
The relative
reactivity of the halogens,
shown in group
trends,
can be shown by displacement
reactions.
These are similar to the metal
displacement reactions
shown on page 5 of the
reactivity series.
For example, when bromine gas
is bubbled through a solution
of potassium iodide in
water, the more reactive
bromine will displace (take the place of) the less
reactive iodide,
forming iodine and potassium bromide.
bromine
+ potassium
iodide
potassium bromide + iodine.
Br2(g) +
2KI(aq)
2KBr(aq) +
I2(s)
Similarly, chlorine will displace less reactive halogens.
Chlorine is more reactive
than both bromine
and iodine and
will displace bromine
and iodine from the appropriate
salt.
Chlorine will displace bromine from sea water.
Chlorine will displace iodine from potassium bromide.
chlorine
+ potassium
iodide
potassium chloride + iodine.
Cl2(g) + 2KI(aq)
2KCl(aq) +
I2(s)
How can Displacement Reactions be written as Ionic Equations?
When the equations are written in terms of ions
they are called ionic
equations. For example, the equation
chlorine
+ potassium
iodide
potassium chloride + iodine.
Cl2(g)
+ 2KI(aq)
2KCl(aq)
+ I2(s)
can be written as
Cl2(g) +
2I-(aq)
2Cl-(aq) +
I2(s)
Potassium iodide, on
the left, exists
in solution as
potassium ions (K+) and iodide ions
(I-)
and
potassium chloride, on the right, exists in solution
as
potassium ions (K+) and chloride ions
(Cl-).
Potassium
ions (or other metal ions) can
be left out of the
ionic equation because they do not
change in the reaction.
Ions that are not changed
during the reaction can be
called spectator
ions, as though they just
sit back and watch!
Links
The Halogens
Revision Questions
gcsescience.com The Periodic Table Index Periodic Table Quiz gcsescience.com
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