DECOMPOSITION
REACTION OF POTASSIUM
CHLORATE
Rafael Prieto Alcón
Rafael Prieto Alcón
DECOMPOSITION OF POTASSIUM
CHLORATE
 Potassium chlorate is a compound composed of
potassium (K), chlorine (Cl), and oxygen (O).
 It melts at 368 ºC and decomposes at 400ºC into
the solid compound, potassium chloride, with
molecular oxygen driven off:
2 KClO3
→
2 KCl
Rafael Prieto Alcón
+
3 O2
DECOMPOSITION OF POTASSIUM
CHLORATE
 Let us heat up a small amount of this chemical in a
test tube.
Haz click en el video para reproducirlo
What do you think has happened?
How can we explain this observation?
Check your answer
Rafael Prieto Alcón
DECOMPOSITION OF POTASSIUM
CHLORATE
 The product melts after a few minutes.
 This is a physical change because we still
have potassium chlorate, but it is a liquid
because it has changed its physical state.
Watch the process again if in doubt.
Rafael Prieto Alcón
Haz click en el video para reproducirlo
Rafael Prieto Alcón
DECOMPOSITION OF POTASSIUM
CHLORATE
 We will keep on heating to see what happens
next.
Haz click en el video para reproducirlo
How can we explain that a solid appears in the tube?
Is that solid potassium chlorate?
Check your answer
Rafael Prieto Alcón
 The fact that a solid appears in the test tube
indicates that a chemical reaction has taken
place.
 That solid is not potassium chlorate,
because this compound has decomposed
as indicated below:
2 KClO3
→
2 KCl
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+
3 O2
DECOMPOSITION OF POTASSIUM
CHLORATE
 We are going to add a few small paper balls into
the test tube.
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Explain what has happened on addition of those
paper balls.
Check your answer
Rafael Prieto Alcón
 The
oxygen
evolved
during
the
decomposition of potassium chlorate is
responsible for the combustion of the small
paper balls.
 This a a typical combustion reaction which is
another type of chemical reaction as we
have already studied.
Rafael Prieto Alcón
THE ROLE PLAYED BY
OXYGEN IN
COMBUSTION REACTIONS
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Combustion reactions
 Oxygen combines with another compounds
to form water and carbon dioxide.
 These reactions are exothermic, meaning
they produce heat. They are usually
accompanied by emission of light.
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Combustion reactions
When wood burns, it must do so in the presence
of O2 and a lot of heat is produced:
O2
Heat
Wood as well as many common items that
combust are organic (i.e., they are made up of
carbon, hydrogen and oxygen). When organic
molecules combust the reaction products are
carbon dioxide and water (as well as heat).
Organic
molecules
O2
wilth C, H and O
CO2 H2O
Rafael Prieto Alcón
Heat
Rafael Prieto Alcón