Investigating the rate of reaction between hydrochloric acid and chalk.
Chris Wirt 09/01/01
Investigating the rate of reaction between hydrochloric acid and Chalk (Calcium
Carbonate)
Aim:
The aim of my investigation is to research into how the reaction between
hydrochloric acid and Chalk (Calcium Carbonate can be effected by changing conditions.
Variables:
These are the variables which I could use in my experiment:
* Changing the surface area of the solids(CaCo).
* Changing the concentration of the reactants(HCL).
* Changing the temperature of the reactants(HCL).
Surface area:
When the surface area for the reaction is changed the speed to the reaction will
increase. As far more of the substance will be able to react at the same time, with the
larger surface area the number of collisions between particles will also be far greater.
Concentration:
Increasing the concentration of the reactant will increase the rate of reaction. This is
due to the fact that there will be a far greater amount of particles in the same amount of
space, increasing the chance of a collision between particles.
Temperature:
Increasing the temperature will increase the rate of reaction. As when the
temperature is increased the energy changes to kinetic energy in the chemical particles.
With more kinetic energy the particles will move much faster.
E.g.
Out of these possible variables I am going to change the concentration of the reactant for
my variable. This is because I feel that I will be able to obtain the most interesting results.
List of apparatus:
* Hydrochloric acid (0.2, 0.4, 0.6, 0.8, 1.0 Molar strength)
* Chalk (Calcium Carbonate) 0.25g measurements
* Clamp stand
* Boss Bolt
* Gas syringe
* 100ml conical flask
* Stop watch
Safe Test:
I will make this a safe test by doing the following:
* Wearing glasses to prevent chemicals from getting in my eyes and causing damage.
* I will roll up the sleeves to my shirt to make sure that they do not get in the way of the
experiment or knock any objects over causing hazard.
* I will make sure that I tuck my tie into my shirt to avoid it catching of objects and
causing hazard.
* I will make sure that when I am carrying chemicals I am careful not to spill them and to
notify a teacher if I do.
Fair Test:
I will make this test fair by doing the following:
* I will make sure this is a fair test by making sure that I use the same amount of reactant
each time.
* I will make sure that when I do it I use the same amount of Chalk (Calcium Carbonate)
each time.
* I will make sure that I do the test over three times for average and to allow for outlying
results.
* I will make sure that when I do the test I use the same amount of hydrochloric acid each
time.
Prediction:
I predict that as I try this experiment with a higher concentration the reaction of the
chalk (Calcium Carbonate) dissolving will become faster. The lower concentration, reactions
will be slower, so as the concentration of the hydrochloric acid becomes greater, faster the
reaction. I predict that if the concentration of the HCL is doubled then the experiment will
happen twice as fast. This is because twice as many HCL particles will be present than
previously and there will be twice as much chance of the calcium carbonate colliding with the
concentrated hydrochloric acid. Therefor when the concentration is doubled the time take
for the reaction should be halved. I think that I will be able to see this clearly in my results. I
think that each time the over all amount of gas given off would be the same due to there
being the same amount of Chalk each time. The rate of reaction should continue to increase
until another factor slows ...
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previously and there will be twice as much chance of the calcium carbonate colliding with the
concentrated hydrochloric acid. Therefor when the concentration is doubled the time take
for the reaction should be halved. I think that I will be able to see this clearly in my results. I
think that each time the over all amount of gas given off would be the same due to there
being the same amount of Chalk each time. The rate of reaction should continue to increase
until another factor slows down the reaction, such as the reactant being exhausted. This is
my prediction for what my graph will look like:
Graph 6
This is a general graph, showing the rough Idea that gas will be produced until a point. Each
of the different strengths should show different graphs. With the higher concentrations having
graphs with steeper slopes, although all of them should finish at roughly the same height, as
the same amount of CaCo is being used each time.
Hypothesis:
For a reaction to take place two particles must collide. For this to happen they
must first have the required activation energy, this is the minimum amount of energy that
they must collide with for a reaction to take place. This activation energy is used to break
some of the bonds in the molecule to allow for newly formed bonds. The more collisions
and the faster they occur the faster the reaction will be. Also for a reaction to take place
the particles must align and fit together, this is called lock and key theory. The lock and
key theory is simply a way of describing how specific an enzyme is for its substrate. Just
like a lock requires a specifically shaped key for it to work so does an enzyme. Because
each enzyme performs a specific task on a specific substrate the active centre of the
enzyme can be considered to be the "lock" which requires the specific "key" or substrate
to perform the function.
When the concentration of hydrochloric acid is increased the number of particles
involved increases and yet the space involved stays the space. This will make the reaction
occur much quicker, as the more particles there are in the same space, the more likely
collisions are. This also is true as an opposite when you lower the concentration of the
hydrochloric acid I think that the reaction will become much slower. This is because the
number of particles in the hydrochloric acid are greatly reduced yet the space stays the
same, making them less likely to collide, and react, causing the reaction between them to
be greatly slowed down.
Method:
. First I will start by measuring out the first 30ml of hydrochloric acid this should be 0.2
molar strength, as that is the lowest molar, there for my starting acid.
2. I will then measure out the first measurement of Chalk (Calcium Carbonate) using the
electronic scales to increase the accuracy.
3. I will then set up the equipment as is shown in my diagram, with the gas syringe ready to
measure the amount of gas given off.
4. Now that all the chemicals and equipment are ready I am able to add the Chalk (Calcium
Carbonate) to the container full of Hydrochloric acid, and place the bung of the gas
syringe over the top. Starting the watch at the same time also.
5. From here I will be able to observe the reaction, taking the measurement for the amount
of gas given off every 5 seconds, I will continue this up until 50seconds have passed
6. I will then be able to record that result and repeat it three times. I will have to repeat each
of these concentrations a total of three times each.
7. Once the first concentration is complete I will be able to do the same for the other
concentrations repeating each of them three times.
8. I will then be able to analyse this information to see patterns in results and spot outlying
results, and calculate averages.
test
test
2
test
3
Average
conc. of acid(M)
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
0.2
0.4
0.6
0.8
Time (s)
0
2
4
7
6
1
3
3
6
6
2
2
7
5
8
1
2
5
6
7
1
20
3
4
0
1
5
5
4
8
7
4
5
9
8
1
3
4
6
9
0
4
30
4
5
1
2
8
6
6
0
1
6
8
1
1
5
5
6
7
1
3
6
40
6
6
2
4
21
6
7
1
2
8
0
2
3
7
5
7
8
2
4
8
50
7
7
3
6
21
9
1
4
4
21
3
2
3
8
7
0
0
3
6
20
60
8
9
3
7
21
9
2
7
6
22
4
3
5
8
8
0
1
5
7
20
70
8
0
5
8
21
0
3
7
9
22
4
4
6
9
8
1
2
6
9
20
80
9
1
6
9
21
1
3
7
9
22
5
4
7
9
8
2
3
7
9
20
90
1
1
8
9
21
2
4
8
9
22
5
5
8
20
8
3
3
8
9
20
00
2
2
20
9
21
5
4
9
9
22
6
5
8
20
8
4
4
9
20
20
10
3
4
20
9
21
5
6
9
9
22
7
6
9
20
8
5
5
20
20
20
20
4
6
20
9
21
6
8
9
9
22
8
6
9
20
8
6
7
21
20
20
30
4
8
20
9
21
7
8
9
9
22
8
7
22
20
8
6
8
21
22
20
40
6
8
20
9
21
8
9
9
9
22
9
7
22
20
8
8
8
22
22
20
50
6
8
20
9
21
8
21
9
9
22
9
8
22
20
8
8
9
22
22
20
60
7
8
20
9
21
9
21
9
9
22
20
8
22
20
8
9
20
22
22
20
70
9
8
20
9
21
9
21
9
9
22
21
20
22
20
8
20
21
22
22
20
80
9
8
20
9
21
20
21
9
9
22
22
20
22
20
8
20
21
22
22
20
90
9
8
20
9
21
21
21
9
9
22
23
20
22
20
8
21
21
22
22
20
200
9
8
20
9
21
21
21
9
9
22
23
20
22
20
8
22
21
22
22
20
210
9
8
20
9
21
21
21
9
9
22
23
20
22
20
8
22
21
22
22
20
220
9
8
20
9
21
21
21
9
9
22
23
20
22
20
8
22
21
22
22
20
230
9
8
20
9
21
21
21
9
9
22
23
20
22
20
8
22
21
22
22
20
Conclusion:
From my results I can say that the concentration of the hydrochloric acid does directly affect
the rate of reaction between itself and Calcium Carbonate (CaCo). I found this in my results
because as I increased the concentration of the acid I was in fact increasing the number of
atoms per measure of acid. So the amount of acid was staying at a constant and yet as the
concentration increased thus so did the number of atoms. This had the affect of speeding up
the reaction, as there were more particles the chance that a collision will occur between the
CaCo and HCL particles is greatly increased. This increase in number of collisions increased
the rate of the reaction, by using up all the energy present at a much faster rate. From the
graphical evidence you can see that in graph 1 for 0.2M HCL, the reaction that is occurring
lasts for up to 200seconds into recording, where as in graph 5 for 1.0M the reaction has
reached its limit at closer to 50seconds. The graphs 2,3 and 4 show the time the experiment
was reacting to be decreasing as the molar increased, so graph 2 (0.4M) finishes reacting at
75seconds, graph 3 (0.6M) finishes reacting at 140seconds and graph 4 (0.8M) finishes
reacting at 130seconds.
Molar (M)
Time finishes reacting (seconds)
0.2
200
0.4
75
0.6
40
0.8
30
.0
50
This table show far more clearly the times at which the reactions ended for each of the
molars. These should show which molar was reacting the fastest as for each molars I was
sure to use the same amount of CaCo this means that the same amount of gas should be
given off each time, so the fastest to finish reacting would be the one with the fastest rate of
reaction. All of the graphs and tables shown support my predictions and evidence. Graph 6
was my prediction of what the graphs would look like and this is fairly accurate, as the
reaction takes place then as the CaCo runs out the line of best fit is shown to plane off this
was shown in my prediction and can be seen in the graphs I have drawn. The contrast seen
between graph 1 to 5 is a change in the time taken for the reaction, the time taken for the
reaction directly relates to the rate of reaction as I was not changing the amount of CaCo
though out the experiment.
Evaluation:
I overall feel that my experiment has been fairly successful, I found out what I wanted and
my predictions were proved in my results. This would count as a good reflection of my
success as my prediction was good and logical with scientific information. Although I do feel
that this experiment was not carried out as accurately as it could have been, mainly due to
uncontrollable conditions. An example of this is that there could have been impurities within
the CaCo or HCL, this would have given me some anomalous results which are unfair. In
my whole experiment I was required to take many recordings, I believe I found a total of 3
anomalous results all while doing 0.8 molar, I repeated these until I found them to fit roughly
into my line of best fit. This is apparent on graph 4, but I do deem the results shown there to
not be too far out to call them anomalous. These slightly out lying results are not far enough
away by my standards to count as anomalous. Overall I think I found that there where far
less anomalous results than I was expecting, as in my experiment I was dealing will many
different recordings I was expecting to find myself repeating many of the results. The main
factor for inaccuracy in my experiment I believe would be human error, as for some parts of
my experiment I was required to accurately measure the CaCo and read off how much gas
had been collected. I would estimate a margin of error for reading off the measurements to
be around 2cm2 as there is a chance that the angle which the tube is looked at from could
affect the measurement though giving a false perspective. Also when the measurement of gas
is rapidly increasing recording the measurement as particular times when the amount of gas is
increasing can be hard. As I possible counter to this I could have repeated the experiment
even more to give a more accurate average. Also when measuring out the CaCo even when
using electric scales there is a chance that some could be dropped while being transported, I
would not expect anything higher than a margin error of 1g to exist, as the level of accuracy
is good when using the electric scales. This error is probably too small of directly affect my
experiment. There are many other factors which could have affected my experiment, mainly
this is going to be when the CaCo is added some gas may be lost by human error, due to
the cap not being placed onto the flask fast enough. Also the Cap may not be placed with
sufficient pressure to stop any escape of gas. These where errors which had to be accepted
and could only be countered by further repetitions, and repetitions of anomalous results.
Another factor which could have had some affect is a change in temperature, but I do not
suspect this would have had any relevancy to my results as I was washing the flask in
between experiments and changing the HCL used. I did measure the room temperature at
29?C and this stayed constant though out the experiment. Apart from doing repetitions of
the experiment I could have attempted to measure the amount of gas every 5seconds rather
than every 10 this would of produced far more results and of a higher quality. Although not
necessarily better as the amount of human error would be far greater with the degree of
difficulty involved when measuring every 5 seconds. There are a number of possibilities for
follow up experiments, as the set up of my experiment is very versatile and I could simply
change one of the other variables:
* Temperature - I could alter the current set-up of my experiment to investigate into how
temperature affects the rate of reaction. This would be done by keeping all of my
experiment the same but rather than changing the concentration I would be changing the
temperature. I would expect to find that as the temperature is increased the rate of
reaction is also increased, as heat causes particles to move faster and so there would be
a greater chance of a reaction.
* Surface area - I could also alter the investigation to research into how the surface area of
the CaCo affects the rate of reaction. This would be done by repeating my experiment by
rather than changing the concentration of the acid I would be changing the amount of
CaCo. I would expect to find that as I increase the surface area the rate of reaction
would increase but take longer to finish the reaction, this is as there will be more particles
to react, increasing the number of collisions yet also increasing the time taken due to the
increase in the amount of reactant.
Bibliography:
My biology work book
Britannica Encyclopaedia
Heinemann modular science for GCSE
Encarta Encyclopaedia