Investigating the Factors that affect the rate of the reaction of marble in hydrochloric acid.
Investigating the Factors that affect the rate of the reaction of marble in hydrochloric acid.
Theory Prediction
For this investigation, I plan on investigating how the concentration of the hydrochloric acid, affects its rate of reaction with marble.
I predict that as the concentration of the hydrochloric acid increases, the rate of the reaction will increase as well, so therefore, the more concentrated the acid, the faster the reaction will become.
I am basing my prediction for this reaction on the collision theory, and according to this theory, an increase in reactant concentration leads to an increase in reaction rate, and a higher concentration means a larger number of particles in a given volume. If there are more particles, there will be more collisions.
More collisions means a larger number of successful collisions. Therefore the reaction rate will increase.
In solutions of higher concentration, and in gases at higher pressure, particles are closer together. They have a greater chance of colliding and because there are more collisions, the reaction rate is greater.
Prediction of results
I predict to get a set of results that will follow this pattern, (while using approximately 3g of marble):
Molarity of hydrochloric acid
Volume of Hydrochloric acid, (cm3) and (time in seconds)
0
20
30
40
50
60
70
80
90
00
0
0
0
0
0
0
0
0
0
0
0
2
6
0
4
8
22
26
30
34
38
2
3
8
3
8
23
28
33
38
43
48
3
4
0
6
22
28
34
40
46
52
58
Graph, showing an increase in rate, with an increase in concentration.
Variables
Although I am investigating how the effect of the concentration of the hydrochloric acid affects the rate of its reaction with marble, there are other factors that may also affect the rate of the reaction, and in order to make my investigation more accurate and reliable, I will control these other variables and keep them constant.
The other factors, which may affect the rate of the reaction of marble in hydrochloric acid, are:
Temperature of hydrochloric acid:
This will affect the rate of the reaction because as the temperature increases, the molecules generate more energy and move around quicker.
This can be backed up by the collision theory, which states that: At higher temperatures, particles are moving faster, so there are more collisions. Also and more importantly, the collisions are more energetic. More collisions have an energy greater than the activation energy, so the reaction is faster.
Surface area of marble:
If the marble chip had a larger surface area, then there would be a larger space for the molecules in the acid to react with, and therefore this will increase the rate of the reaction. If the marble chip had a small surface area, then there would be a small area for the molecules in the acid to react with, and therefore this will slow down the rate of the reaction.
This can be backed up by the collision theory, which states that: With a greater surface area of solid, collisions are ...
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Surface area of marble:
If the marble chip had a larger surface area, then there would be a larger space for the molecules in the acid to react with, and therefore this will increase the rate of the reaction. If the marble chip had a small surface area, then there would be a small area for the molecules in the acid to react with, and therefore this will slow down the rate of the reaction.
This can be backed up by the collision theory, which states that: With a greater surface area of solid, collisions are far more frequent. Because there are more collisions, the reaction rate is greater.
.
As I stated earlier, all the variables listed above may affect the rate of the reaction, so I will try to keep all of them constant while I investigate how the concentration of the hydrochloric acid will affect the rate of the reaction.
Apparatus
For this investigation I will require:
2 beakers
2 clamps and stands
100cm3 gas syringe
2 measuring cylinders
electrical balance
boiling tube with side arm and a cork that fits.
stopwatch
delivery tube
Before starting the experiment, make sure the gas syringe is placed in such a way that you can see and read the numbers on it.
Method
* Set up the apparatus as shown on the previous page, and mix the various concentrations of the acid that is required.
(Usually the lab will supply 2m, and 4m, so I don't have to make those concentrations myself)
I am using 10cm3
Molarity of solution
M
Amount of acid present in solution
Cm3
Amount of water present in solution cm3
.5
2.0
5 (4M)
5
2.5
7.5 (3M)
2.5
3.0
7.5 (4M)
2.5
3.5
8.75 (4M)
.25
4.0
0 (4M)
0
0.0
0
0
* Weigh out 16 portions of marble of 2g
* Pour 10cm3 of 1.5m acid into the tube, and then at the same time: put in a portion of marble (2g), and set the stopwatch on.
* Record the reading on the gas syringe after every 10 seconds, in a results table, that should look like this.
Molarity of hydrochloric acid (M)
Volume of Hydrochloric acid, (cm3) and (time in seconds)
0
20
30
40
50
60
70
80
90
00
0
2
3
* After 100 seconds, remove the tube, pour its contents into a residue beaker, and repeat the experiment, using a different concentration of acid.
* Repeat this experiment twice to get two sets of results.
*For safety always wear goggles, and run you're hands in cold water immediately if there is a spillage of acid on them. Do not let the acid come in contact to your clothes, as it causes holes in them.
*Do not clamp the apparatus up too high, in case it falls down, so that the syringe doesn't break, and/or the glass delivery tube doesn't shatter. (making it more difficult to clear up)
Results
Experiment 1
Molarity of hydrochloric acid
Volume of Hydrochloric acid, (cm3) and (time in seconds)
0
20
30
40
50
60
70
80
90
00
0
0
0
0
0
0
0
0
0
0
0
.5
3
5
7
9
2
4
7
9
23
2
2
5
8
3
7
21
26
29
33
36
2.5
3
6
2
9
25
31
35
40
46
50
3
4
0
20
27
33
41
47
53
60
65
3.5
5
2
22
30
41
49
55
63
68
77
4
6
5
24
35
45
53
63
70
78
85
Experiment 2
Molarity of hydrochloric acid
Volume of Hydrochloric acid, (cm3) and (time in seconds)
0
20
30
40
50
60
70
80
90
00
0
0
0
0
0
0
0
0
0
0
0
.5
3
5
7
0
3
5
8
21
25
2
2
5
0
4
8
23
27
31
35
37
2.5
3
9
5
20
27
32
38
43
45
51
3
4
0
7
25
31
39
46
52
58
63
3.5
5
2
22
30
41
49
55
63
68
77
4
7
6
25
36
44
52
64
72
80
87
Average Results
Molarity of hydrochloric acid
Volume of Hydrochloric acid, (cm3) and (time in seconds)
0
20
30
40
50
60
70
80
90
00
0
0
0
0
0
0
0
0
0
0
0
.5
3
5
7
9.5
2.5
4.5
7.5
20
24
2
2
5
9
3.5
7.5
22
26.5
30
34
36.5
2.5
3
9.5
3.5
9.5
26
31.5
36.5
41.5
45.5
50.5
3
3
0
8.5
26
32
39
45.5
51
57.5
62.5
3.5
5
2
22
30
41
49
55
63
68
77
4
6.5
5.5
24.5
35.5
44.5
52.5
63.5
71
79
86
Analysis
I repeated this experiment twice, so that I could crosscheck my results against each other, and be able to make up an average result.
I plotted four graphs in total.
The first for experiment 1,
The second for experiment 2,
The third for the Average results, and
The fourth for the Rate Graph
All three of the first graphs were relatively the same, and this meant that my 2 results were too an extent accurate enough, to be trusted, and used to support my hypothesis.
In my hypothesis I predicted that as the concentration of the hydrochloric acid increases, the rate of the reaction will increase as well, so therefore, the more concentrated the acid, the faster the reaction will become.
I based this prediction on the collision theory, which states that in solutions of higher concentration, and in gases at higher pressure, particles are closer together. This means that they have a greater chance of colliding and because there are more collisions, the reaction rate is greater.
The results I got from this experiment, although not completely accurate, tally with the collision theory, therefore my results support my predictions and to some extent have proven them right.
However in my predicted results, I predicted that the amount of gas being produced would go up equally, as the concentration and time increased. This was not the case in the results I got, and I noticed that the amount of gas being produced went up randomly, with no obvious pattern.
Evaluation
Over all I am quite pleased with my investigation, but I am not very satisfied with my results, although they proved that I had made some accurate predictions in my hypothesis.
The procedure I used was quite safe (as long as the safety precautions were followed), and the results were quite similar to my predicted results, as they followed the trend, of the rate of the volume of gas being produced, increasing with an increase of the concentration.
I have no solid explanation on why my results were not completely perfect but I could explain some of the probable causes:
Temperature
For this investigation, I did not investigate the effects of temperature on the rate of the reaction, but I predicted that temperature may affect my experiment/results. I backed up this prediction using the collision theory, which states that at higher temperatures, particles are moving faster, so there are more collisions. Also and more importantly, the collisions are more energetic, and more collisions have an energy greater than the activation energy, so the reaction is faster.
For this entire Investigation, I did not check the temperature of the acid, and I carried out the practical investigation on 2 different days, which probably had 2 different temperatures, and this could have caused inaccuracy in my results.
Surface area
I did not investigate the effects of what different surface areas would have on the rate of the reaction, but in my plan, I predicted that different surface areas might affect my experiment/results, and I backed up this prediction, using the collision theory, which states that with a greater surface area of solid, collisions are far more frequent, and because there are more collisions, the reaction rate is greater.
While carrying out this experiment, although I weighed out all the marble chips to 2g before using them, I did not take into consideration the effects of different surface areas, and instead of looking for relatively standard sized chips. I used a combination of big, medium, and small.
However even if I had chosen a standard size of chip (e.g. medium), the surface area will still be a problem, because I wouldn't be able to measure its area accurately enough.
Except for the two problems of: not standard surface area, and unregulated temperature, I would have to say that my experiment went quite well.
My results although not very accurate, can still be used to support my predictions, and the collision theory.
The aim of this experiment was: To investigate how and whether the concentration of the hydrochloric acid, affects its rate of reaction with marble (calcium carbonate)
Due to this investigation, I can conclude that: the rate of the reaction of marble with hydrochloric acid is affected by the concentration of the acid, and this is because, as I have proven in this investigation, the more concentrated the acid, the faster the marble reacts, and the faster a gas is produced (carbon dioxide).
If I had a chance to re-do this experiment, I would not change my procedure or plan completely, but I will add to it by regulating the temperature, and if that proves to difficult, I will aim to complete the experiment in 1 day, in order to have approximately the same temperature, throughout the experiment.
I will then try to use a standard size of marble, because it will be too difficult finding out the surface area of the chip, and instead of measuring the amount of gas produced every 10 seconds, I will make the experiment easier and less complicated, by measuring how long it takes to produce a particular amount of gas, with different concentrations of acid.
