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Chemistry Catalyst Investigation :: Papers

作者:ihpa.net 发布时间:2017-09-24

solution to create the different concentrations of hydrogen peroxide.
The total amount of solution in the conical glass will be the same in
each test; this will keep the test fair. Finally to keep the test
fair, I will start my timer as soon as the bung is firmly secured into
the conical glass. This will make the test fair as before the bung is
on the conical glass, the reaction between the two reactants has
already started. Therefore O2 gas is already being produced and is
escaping out of the top of the conical glass. By starting the timer
when we put the bung on the conical glass we will not record the gas
that has already escaped, only the O2 gas which is taken via the
delivery tube into the burette.

Apparatus:

· Tripod x2

· Clamp x2

· Spatula

· Small Tray

· Bung

· Pan

· Measuring Cylinders x2

· Measuring beaker

· Safety glasses

· Burette

· Balances

· Conical Glass

· Delivery Tube

1. Put on your safety glasses, these will protect your eyes from the
hydrogen peroxide. This solution acts as bleach and will create a very
painful sting if brought in contact with the eye. Also, keep out of
contact with skin as it can sting and it creates white spots on the
surface.

2. Set up the apparatus as shown on the previous page, placing the
Burette carefully on top of the end of the delivery tube, therefore
oxygen will climb up the burette when the reaction takes place.

3. Now, its time to collect your manganese. Due to my preliminary, I
discovered that using 1g of manganese with different concentrations of
hydrogen peroxide leads to a far too reactive experiment. So I tried
0.5g and discovered the experiment was still far too reactive. So
collect 0.1g of manganese with a spatula (to be fairly accurate and
tidy, you won't spill the manganese with a spatula). If manganese does
get spilt do not wipe it up with a damp paper towel, this will spread
it further. Use a brush and pan.

4. Put the manganese aside whilst you next measure the first
concentration of the hydrogen peroxide. Take your two measuring
cylinders; mark on one of these a W for Water and H on the other for
Hydrogen Peroxide with marker. This is so you do not mix the measuring
cylinders up in experiments, because if you were to use a cylinder for
collecting water which had been previously been used to collect
hydrogen peroxide, there might be a little hydrogen in the cylinder.
If this is the case, then when you come to mix the solutes together,
you will end up with more hydrogen peroxide than intended. This will
not be accurate. For each test, the solution of water and hydrogen
peroxide will be 40ml. The concentrations of hydrogen peroxide we will
use are 0%, 10%, 20%, 30%, 40%, 50% and 60%. I chose these
concentrations as due to my preliminary experiment I know that with
0.1g of manganese any concentration above 60% reacts too quickly. Here
is a table to show how to create these concentrations:

CONCENTRATION (%)

HYDROGEN PEROXIDE

(ml)

DISTILLED WATER

(ml)

TOTAL SOLUTION

(ml)

0

0

40

40

10

4

36

40

20

8

32

40

30

12

28

40

40

16

24

40

50

20

20

40

60

24

16

40

So to create your first solution of 0% concentration, fill one of the
measuring cylinders with 40ml of distilled water and leave the other
empty. This solution will not create a reaction as there is no
hydrogen peroxide, but it will act as a control.

5. Now, pour the 40mls of distilled water into the conical glass, with
all your apparatus set up properly, with your delivery tube connecting
the conical glass to the bottom of your burette. Make sure you have
your timer at the ready.

6. Have your results table and a pen at the ready.

7. Now in rapid succession, pour your 0.1g of manganese into the
conical glass and put on the bung. As soon as the bung has firmly been
placed on the top of the conical glass start the timer.

8. Every 10 seconds record how much oxygen has been given off from the
reaction, (the amount of water lost in the burette). Time for two
minutes.

9. Repeat steps 3-8 with all the other concentrations.

Prediction

I predict in this experiment, that the higher concentration of
hydrogen peroxide used, the more oxygen there will be produced from
the experiment every 10 seconds. I predict this because with more
concentration there will be more particles for reactions to take
place. In my investigation I am not changing the amount of catalyst,
in every test I will only use 0.1g of manganese, catalyst. We decided
to use this amount because in my preliminary work I discovered that
anything above this mass is too reactive, especially when I used
anything above 0.5g of manganese. On Page 208 in GCSE Chemistry For
You a catalyst is described as:

" A catalyst is a substance which speeds up a chemical reaction. At
the end of the reaction, the catalyst is chemically unchanged".

When a chemical reaction takes place, two particles of different
substances collide with each other. Every time particles collide they
produce energy. However, they need to create a certain amount of
activation energy to create a reaction. E.g.


Energy
------

[IMAGE]


[IMAGE]
-------


By adding a catalyst, the activation energy needed for a successful
collision and reaction is reduced. Therefore during a collision, less
energy needs to be created for a successful collision. Here is how
much energy a catalyst reaction needs compared to a usual one with no
catalyst.


Energy
------

[IMAGE]


When the particles collide at slower rates they produce less energy
than particles travelling at faster rates. Therefore, particles
travelling faster have a higher chance of creating the activation
energy needed. One way to make the particles travel faster is to heat
them. This gives the particles more energy to reach the activation
energy needed for a collision. Another way of speeding up the rate of
reaction is by making the concentration of the hydrogen peroxide
greater. This will not give the particles more energy but by
increasing the concentration there will be more hydrogen peroxide
particles for the manganese particles to collide with, therefore there
will be more collisions with a higher concentration. This is the
variable we are changing. With the activation energy needed for a
reaction being reduced by the catalyst, the collisions taking place
will not need as much energy. So hence more reactions will be
successful and the rate of reaction between the manganese and hydrogen
peroxide will be increased.

KEY (throughout diagrams):

= H20 molecule (from solution).

= Hydrogen Peroxide particles (from solution).

= Manganese particles (catalyst).

With a lower concentration of hydrogen peroxide, there will be less
particles of hydrogen peroxide for the manganese to collide with,
produce energy, and create a successful reaction with. The diagram
below shows a low concentration of hydrogen peroxide in the conical
glass with 0.1g of manganese.

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As you can see there are very little hydrogen peroxide particles to
create successful collisions with the manganese particles. However,
with a more concentrated solution of hydrogen peroxide, there will be
more hydrogen peroxide particles, therefore there will be more for the
manganese to react with. This diagram below shows this:

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This is why I believe that with more concentrated solution the rate of
reaction will be faster. Therefore, every 10 seconds more oxygen will
be produced by the catalysed reaction with a higher concentrated
solution.

With the knowledge I have, due to my preliminary experiment and
prediction, I predict that my graph showing how the different
concentrations of hydrogen peroxide affect the rate of the catalysed
reaction between hydrogen peroxide and manganese will look like this:

[IMAGE]


I predict there will be a positive correlation between the
concentrations of hydrogen peroxide and the rate of reaction.

[IMAGE]

Concentration (%)


Results:

Time

(Secs)

Oxygen Produced From Reaction In The Different Concentrations Of
Hydrogen Peroxide (cm )

10%

20%

30%

40%

50%

60%

10

0.0

1.0

3.2

0.4

7.5

3.2

20

1.0

5.0

11.8

4.9

21.8

15

30

1.9

9.0

18.2

9.9

31

26.3

40

3.0

13.0

24.3

16.3

40.5

34.5

50

3.9

17.0

29.4

22.8

49.4

44.5

60

4.9

19.7

34.2

28.5

50.0+

50.0+

70

5.7

22.8

38.2

34.0

50.0+

50.0+

80

6.5

25.5

42.7

38.4

50.0+

50.0+

90

7.2

28.0

46.8

43.4

50.0+

50.0+

100

8.0

30.6

50+

47.9

50.0+

50.0+

110

8.9

33.2

50.0+

50.0+

50.0+

50.0+

120

9.4

37.8

50.0+

50.0+

50.0+

50.0+

Analysis:

In this investigation I found that with a more concentrated hydrogen
peroxide solution the rate of reaction between hydrogen peroxide and
manganese increases and produces more oxygen. This is as I predicted.
Here is a graph to show this more clearly:

Graph:

From my graph I have spotted a couple of trends. Firstly all the lines
of best fit have a positive correlation on the graph. Secondly as the
hydrogen peroxide concentration in the solutions increase in strength
the lines of best fit become steeper. The final trend that I spotted
is that on every line, before the line of best fit becomes straight
there is a section that looks like this:

[IMAGE]

[IMAGE]


This is an interesting shape as strictly speaking if I carried out the
investigation accurately then the lines should be straight from the
origin of the graph to the point where it exits the graph. So this
means I did not carry out the experiment 100% precisely. In fact the
stage in my method where I went wrong was step 7, it states:

"Now in rapid succession pour your 0.1g of manganese into the conical
glass and put on the bung. As soon as the bung has firmly been placed
on the top of the conical glass start the timer."

I followed this step exactly just as I did with the others, but the
problem is within the step itself. I wrote "in rapid succession pour
your 0.1gs of manganese into the conical glass and put on the bung".
It takes a couple of seconds to pour all the manganese into the
conical glass and around half a second to put the bung on the conical
glass. This means the reaction starts 2 and a half seconds before the
bung is on. Hence this means the reaction is in process and oxygen is
being produced 2 and a half seconds before the bung is secured onto
the conical glass. Therefore oxygen that is being produced is being
lost through the top of the conical glass rather than being measured
in the burette. This means that only when the bung is placed on top of
the conical glass can the oxygen be measured properly. However, my 7th
step also states to only start the timer when the bung has been placed
on top of the conical glass. This is the point of the 7th step were I
did not follow the step accurately. I did not start the timer exactly
when the bung was firmly on in each experiment, sometimes I did do it
right but in some tests I started it a couple of seconds later or
earlier. This is why I gained a mixed variety of starts on my lines of
best fits. So the reason why the reactions did not appear to start on
my graph for a few seconds was that oxygen escaped before the bung was
placed on the conical glass. But, on my graph the reactions do not get
going for around 20 seconds. This is because it takes time for the
oxygen to travel up the burette, more than 10 seconds on average and
as I only measured the amount of oxygen produced every 10 seconds, in
most of the reactions I only received a reading other than zero at 20
seconds.

As all the lines of best fit have a positive correlation on my graph
this shows that as the hydrogen peroxide concentration in the
solutions increase in strength the lines of best fit become steeper.
Meaning that with more hydrogen peroxide concentration more oxygen is
produced in the reaction. If more oxygen is being produced then there
is a faster rate of reaction. Therefore my prediction was right by
saying that the higher concentration of hydrogen peroxide used, the
more oxygen there will be produced from the experiment every 10
seconds. This happens because when there is a solution with a larger
hydrogen peroxide concentration solution there are less H20 molecules
and more hydrogen peroxide particles in the solution. Therefore when
the solution is placed in the conical glass with the manganese, there
are more hydrogen particles for the manganese particles to collide
with, produce the activation energy needed and finally react with.

[IMAGE]


However, with a lower concentration of hydrogen peroxide in the
solution, there will be less particles of hydrogen peroxide for the
manganese particles to collide with, produce energy, and create a
successful reaction with. The diagram below shows a low concentration
of hydrogen peroxide in the conical glass with the manganese.

[IMAGE][IMAGE]

[IMAGE]


So this is why the more concentrated hydrogen peroxide solutions
created a faster rate of reaction with the manganese, therefore
creating more oxygen every 10 seconds.

However, to state the above and back up my prediction, I only looked
at the steepness of the lines, not where they are positioned on my
graph. As on my graph I have some interesting positioning of lines. It
shows that the 30% hydrogen peroxide concentration produced more
oxygen in 120 seconds than the 40% solution. Which is true in our
experiment but if you look carefully at the two lines from 20 seconds
the 40% hydrogen peroxide solution has the steeper gradient indicating
that it produced oxygen at a faster rate. This is the same case with
the 50% and 60% hydrogen concentrations as on my graph it shows that
the 50% hydrogen peroxide concentration produced more oxygen within 50
seconds but from 20 seconds the 60% hydrogen peroxide concentration
has the steeper gradient line again indicating that it is producing
oxygen at a faster rate.

This is because of the three reasons I stated earlier, the reaction
starts around 2.5 seconds before the bung is on the conical glass, it
takes time for the oxygen gas to travel up the burette and the fact
that I did not start the timer exactly at the same time on every
experiment. Take a look at the lines of best fit I gained for the 50%
and 60% hydrogen peroxide concentration. They look like this:

[IMAGE]


[IMAGE]


I believe that the reason that the 50% hydrogen peroxide solution
started off more quickly is because I started the timer after the bung
had been placed on the conical glass. Therefore I would not have
recorded any of the oxygen lost through the top of the conical glass
before the bung was placed on it and I would not have recorded some of
the time it took for the oxygen to travel up the burette. I believe
that the 60% hydrogen peroxide concentration had a slow start to the
reaction as I started the timer as soon as the first particles of the
manganese made contact with the hydrogen peroxide. Therefore I did
record the oxygen that escaped through the top of the conical glass in
this experiment so hence no oxygen was taken into the burette for the
first few seconds.

So as it took 20 seconds to get proper readings I am going to make
another graph. My graph shows the time against the amount of oxygen
produced, this shows my results clearly but my aim in this
investigation was to find out how different concentrated hydrogen
peroxide solutions affect the rate of the catalysed reaction. As it
took 20 seconds to get proper readings I am only going to use the
readings after 20 seconds when I work out the rates of the reactions.
To work out the rate of reactions you do this:

[IMAGE]


So the rates of reactions for my different concentrations are shown
below in the table.

Concentration Of Hydrogen Peroxide

(%)

X

Y

Rate Of reaction (X·Y)

To 1dp

10

8.4

100

0.1

20

34.5

100

0.3

30

38.0

72.0

0.5

40

45.0

80.5

0.6

50

29.4

30.4

1.0

60

37.5

34.2

1.1

Graph showing these results:

My graph of results is exactly how I predicted it to be in my
prediction. It shows there is a positive correlation between the
concentrations of hydrogen peroxide and the rate of the reactions.

In conclusion, in this experiment I have fulfilled my aim and I have
discovered that with more concentrated hydrogen peroxide solutions the
rate of reaction between hydrogen peroxide and manganese is quicker.

Evaluation:

I believe in this experiment that my method worked very well, it was a
great guideline to follow and collect my results. My results were
accurate but they were not 100% accurate as I did receive anomalies on
my last graph that compared the rate of reaction to the different
hydrogen peroxide concentrations.

My method was accurate as I used accurate apparatus to measure amounts
of substances needed in this investigation. For example to collect the
0.1grams manganese needed for each experiment I used a set of
electronic scales which measure to 0.01 of a gram, this ensured that I
had exactly 0.1g of manganese, nothing more or less as if I had had
either 0.09g or 0.11g it would have made the test unfair. To measure
my solutions I used measuring cylinders and pipettes, both of which
have clear scales on the side of them ensuring that I got the right
amount of hydrogen peroxide and water in each solution. And also
ensuring that my solution added up to 40mls in each and every test,
therefore making the investigation fair. I also used a burette to
measure the oxygen that was produced from the reaction; this was
accurate as it has a scale on the side of it. But I did discover that
with 0.1g of catalyst it became very hard with the higher
concentrations of hydrogen peroxide to record the measurements of the
oxygen being produced on the burette. I found this hard, as the rate
of reaction is fairly quick with the higher concentrations of hydrogen
peroxide. Therefore larger amounts of oxygen are produced every 10
seconds and the water level in the burette sinks more rapidly. This
would have been bearable and I possibly would have been able to get
accurate results but when the burettes are set up in the experiment
the scales on them are upside-down. So when I tried such
concentrations as 90% and 100% it was difficult to get accurate enough
results. This is why I only used concentrations up to 60% in my
experiment.

In my experiment, even with all of these accurate measurements made by
accurate equipment I managed to gain two anomalies. They are both
circled in red on my final graph. They are anomalies as all the other
plots on this graph are very close to the line of best fit, whereas
these two plots are a good way from it. I do not believe I gained
these anomalies due to starting the timer before or after when I was
supposed to as I ignored the first 20 seconds of each test when
drawing this graph. Therefore there must be a different reason; there
are a number of possibilities:

· The wrong amounts of hydrogen peroxide and water were used in the
solution.

· The wrong mass of manganese was used.

· Temperature was not the same as in the other experiments.

· Apparatus did not work efficiently.

The first three possible reasons can be ruled out without doubt. I
used accurate pipettes to measure the solutions, I used accurate
electronic scales to measure the mass of catalyst and each and every
test was carried out at room temperature. This leaves the last option.
Throughout the 10%, 20%, 30% and 40% hydrogen peroxide concentration
experiments I used a conical glass with a plastic joint connecting
itself to the delivery tube, e.g:

I was not told until after the 40% experiment that the conical glasses
with plastic joints do not tend to work as well as the ones with glass
joints. So without thinking I changed it for one with a glass joint
for the 50% and 60% hydrogen peroxide concentrations, if these are
better then the ones with plastic joints this could have affected the
results that I gained. This is why I believe I gained these anomalies
for the 50% and 60% concentrations.

I feel that my method was good to follow and that it lead to accurate
results. I followed it throughout the experiments and I only went
wrong when I did not follow my method correctly. I did make it very
clear to start the timer when the bung is placed on top of the conical
glass:

" 7. As soon as the bung has been placed firmly on top of the conical
glass start the timer."

It was my big mistake not to follow this accurately when I started the
timer before or after the bung was firmly secured. The only fault I
can see in my method is that I do not actually show what the results
table should look like. To make it more clear between steps 2 and 3 I
would have added another one saying:

· Before measuring out any of the substances draw your results table
down on a piece of paper. As in this experiment the concentrations you
will use are 10%, 20%, 30%, 40%, 50% and 60% and you will record data
every 10 seconds for two minutes. Draw a results table as shown below:

Time

(Secs)

Oxygen Produced From Reaction In The Different Concentrations Of
Hydrogen Peroxide (cm )

10%

20%

30%

40%

50%

60%

10

20

30

40

50

60

70

80

90

100

110

120

This would have made my method a lot clearer. However, one problem
that was unavoidable was the fact that it took some time for the
oxygen to travel up the burette before the first reading could be
gained. Unless you start the timer when the first bubble reaches the
top of the burette this is unavoidable. Another problem that was
unavoidable with the apparatus I used, was when I started the timer
before the bung was on in one of the tests, oxygen escaped out through
the top of the conical glass. As I explained in the analysis, it takes
time to pour the manganese into the solution and to put the bung on
the conical glass. During this time the reaction is already underway
and because there is no bung on top of the conical glass oxygen gas
escapes. This is inaccurate, as this gas should be measured. A
solution to this is to measure out the manganese and then put it in a
vile. Then by placing the vile in the solution no reaction will occur
because the manganese and hydrogen peroxide are not actually in
contact with each other. Once the bung is on the conical glass with
the solution and vile inside you can shake the conical glass gently.
This will knock over the vile and the manganese inside it will come
into contact with the hydrogen peroxide solution. As the bung is on no
gas will escape and it will all go and be measured in the burette. The
diagram below shows this:

My conclusion of the rate of reaction increasing with more
concentrated hydrogen peroxide solutions is 100% reliable. There is no
doubt about it as on both graphs the lines of best fit showed positive
correlations. Because I believe my method worked well I believe that
it lead to accurate results and this is why I believe my conclusion is
100% accurate. I believe I gained the anomalies due to the two
different conical glasses we used as I explained earlier in the
evaluation. But these anomalies still show a positive correlation
between the plots therefore backing up my conclusion.

To extend this investigation I would investigate how the concentration
of hydrogen peroxide solution affects the rate of reaction between
itself and different chemical catalysts. This would enable me to
compare the two conclusions I receive, and I would be able to see if
the rate of reaction between hydrogen peroxide solution and a catalyst
always increases with a higher concentration of hydrogen peroxide in
the solution. I would carry out my method for each different catalyst,
I would draw the graphs for each catalyst showing the amount of O2
produced every 10 seconds against time, and then I would work out the
rates on each line of best fit on the graph (as I did in this
experiment) by calculating X·Y= RATE. After doing this for each
different catalyst with the different concentrated hydrogen peroxide
solutions I would be left with a number of different results tables
showing the rate of reaction with the catalyst used against the
concentrations used. E.g. in this experiment the table looked like
this:

MANGANESE:

Concentration Of Hydrogen Peroxide

(%)

X

Y

Rate Of reaction (X·Y)

To 1dp

10

8.4

100

0.1

20

34.5

100

0.3

30

38.0

72.0

0.5

40

45.0

80.5

0.6

50

29.4

30.4

1.0

60

37.5

34.2

1.1

With all these different results tables I could plot a final graph
just like the one plotting the rate of reaction against concentration
of hydrogen peroxide solution. Just like the one I made in this
investigation but with all the catalysts displayed on it. If with all
catalysts, more concentrated hydrogen peroxide solutions speed up the
rate of reaction, then all the lines of best fit from all the
different catalysts will be on top of each other and they will all
show a variety of positive and negative correlation. If not the lines
will be scattered and will show negative correlation. E.g.

[IMAGE]Graph showing that with all catalysts more concentrated
hydrogen peroxide solutions speed up the rate of reaction:

Rate Of Reaction

[IMAGE]

Concentration Of Hydrogen Peroxide


Graph showing that increased concentration of hydrogen peroxide does
not speed up the rate of reaction between itself and manganese:

[IMAGE]

Rate Of Reaction

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