Transcript 4.5 Catalysts

13 April 2015
4.5 Catalysts
• A catalyst speeds up the rate of a
chemical reaction.
• A catalyst is not used up during a
chemical reaction.
Decomposition of Hydrogen Peroxide
• Hydrogen peroxide decomposes into water
and oxygen.
Hydrogen peroxide
2H2O2(aq)


water
+ oxygen
2H2O(l)
+ O2(g)
Oxygen gas is given off and can be measured
using a gas syringe or a balance.
The reaction is catalysed by a wide range of
solids.
Remember the catalyst NEVER produces
more product - just quicker
Comparing catalysts
1. Measure out 25 cm3 of
hydrogen peroxide and put it
into the conical flask.
2. Finely chop some celery and
put into the flask.
3. Quickly connect the bung to
the gas syringe and note the
volume of gas produced every
ten seconds for two minutes.
4. Repeat with chopped liver.
5. Repeat with manganese
dioxide.
Excel sheet available – click
on Results
Results
Time
(seconds)
0
10
20
30
40
50
60
70
80
90
100
110
120
Gas produced with
celery (cm3)
Gas produced with liver
(cm3)
Gas produced with
manganese dioxide
(cm3)
Graph
• Draw a graph of your results.
• What type of graph should it be?
• Remember to include
– Title
– Labels for each axis
– Units for each axis.
Which was the best catalyst?
Celery
Liver
Manganese (IV) oxide
4.5 Catalysts
13 April 2015
True or false?
How to play:
• Put your hand up for true,
leave your hand down for false.
• Keep track of your score.
A catalyst is a substance that
speeds up a chemical reaction
but is not used up in the
reaction.
TRUE
Most of the catalysts used in
industry are acids.
FALSE – transition metals
are mainly used.
The catalyst used in the Haber
process is iron.
TRUE
The decomposition of hydrogen
peroxide can be speeded up by
adding a catalyst.
TRUE
Catalysts can become poisoned
by impurities in the reaction so
they need to be replaced.
TRUE
Catalysts work by increasing
the number of collisions
between reactant particles.
FALSE – they lower the
energy needed to react.
Catalysts are usually cheap as
they are readily available.
FALSE – they are expensive
as they are made of precious
metals.
There is a catalyst for every
reaction.
FALSE – not every reaction
has a suitable catalyst.
What is your score out of 8…?
Try to beat your score next
time or get 100% again!
4.5 Catalysts
13 April 2015
• A catalyst speeds up the rate of a
chemical reaction.
• A catalyst is not used up during a
chemical reaction.
Homework: Find out what the catalyst materials used in cars are.