Find out the effect of concentration on the rate of reaction of limestone with hydrochloric acid.
AIM
In this investigation my aim is to find out the effect of concentration on the rate of reaction of limestone with hydrochloric acid.
Calcium Carbonate + Hydrochloric Acid --> Carbon Dioxide + Calcium Chloride
(Limestone) + Water
CaCO3 + 2HCL --> CO2 + CaCl2 + H2O
VARIABLE
. Temperature:
When the temperature is increased, the particles all move more quickly. But if they're moving quickly, they're going to have more collisions.
2. Concentration:
If the solution is made more concentrated it means there are more particles of reactant knocking about between water molecules, which makes collisions between important particles more likely. In a gas, increasing the pressure means the molecules are more squashed up together so there are going to be more collisions.
3. Surface Area
If one of the reactants is a solid then breaking it up into smaller pieces will increase its surface area. This means the particles around it in the solution will have more area to work on so there'll be more useful collisions.
4. Catalyst
A Catalyst works by giving the reacting particles a surface to stick to where they can bump into each other. This obviously increases the number of collisions as well.
PREDICTION
In my prediction, I predict that the higher the concentration of Hydrochloric Acid (HCL) the faster the reaction will be. However if I decrease the concentration of hydrochloric acid the reaction will be slower. Therefore if the concentration of Hydrochloric Acid is doubled, the rate of reaction will be doubled as well.
HYPOTHESIS
The more concentrated the solution of the hydrochloric acid the faster the rate of reaction. Also the more dilute the concentration of hydrochloric acid the slower the rate of reaction. We can also predict that by doubling the concentration we can double the rate of reaction.
For example;
40
Rate of
Reaction
20
Increasing Double
0
20 40
Volume of concentration % (not drawn to scale)
The graph shows how the concentration affects the rate of reaction
The graph above explains that my hypothesis is correct. It also indicates how the graphs of the results obtained will look like. The graph clearly shows that if the volume of concentration increases (or doubles) the rate of reaction will also increase (or double).
BACKGROUND KNOWLEDGE:
Collision Theory:
> All Chemical reactions can only occur when reacting particles collide with each other. They can only achieve this by having a sufficient amount of energy to react.
> ACTIVATION ENERGY is when there is a minimum amount of energy, which is required to cause this kind of reaction.
> The four main important factors which affect the RATE OF REACTION are;
. TEMPERATURE OF THE REACTANTS:
When temperature increases, the particles move faster:
> This results in an increased amount of collisions, and an increased rate of reaction.
> It also results in the particles to collide even more energetically and therefore it is more likely to react.
2. CONCENTRATION OF REACTANTS:
Increased concentration means an increased number of particles:
> This results in an increased amount of collisions, and an increased rate of reaction.
> When increasing the pressure of gases reacting, it also increases the concentration of the particles and the rate of reaction.
3. SURFACE AREA OF SOLID REACTANTS:
When there are smaller pieces, there is a greater chance and area for contact between the particles.
> This results in an increased amount of collisions, and increased rate of reaction.
> The reactions can only ...
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2. CONCENTRATION OF REACTANTS:
Increased concentration means an increased number of particles:
> This results in an increased amount of collisions, and an increased rate of reaction.
> When increasing the pressure of gases reacting, it also increases the concentration of the particles and the rate of reaction.
3. SURFACE AREA OF SOLID REACTANTS:
When there are smaller pieces, there is a greater chance and area for contact between the particles.
> This results in an increased amount of collisions, and increased rate of reaction.
> The reactions can only take place at the exposed and outer surface of a solid.
4. THE USE OF A CATALYST:
A catalyst is a substance which;
> Increases the rate of a chemical reaction, without being used up in the process.
> All catalysts are different. For example, different reactions need different catalysts.
A catalyst lowers the amount of energy needed for a successful collision so more collisions will be successful and the reaction will be faster. It also provides a surface for the molecules to attach to, thereby increasing their chances of bumping into each other.
LIMESTONE:
Limestone is chemically known as Calcium Carbonate. It is used in the manufacture of cement by heating it with clay. Calcium Carbonate is also used in the manufacture of Iron, Sodium Carbonate, Glass and also concrete. Limestone is great for making blocks for building with. Fine old buildings like cathedrals are often made purely from limestone blocks. Acid rain can be a problem though. Limestone is a sedimentary rock, formed mainly from seashells. It is mostly Calcium Carbonate; Limestone is also used as a building material. Limestone and clay are heated to make cement. Limestone is the most abundant of the non-classic sedimentary rocks. Limestone is produced from the mineral calcite (Calcium Carbonate) and sediment.
The main source of limestone is the limy ooze formed in the ocean water or it can be formed from sea creatures that secrete lime such as algae and coral. Chalk is another type of limestone that is made up of very small single celled organisms. Chalk is usually white or grey in colour. Acids can easily dissolve limestone. If you drop vinegar on limestone it will fizz. Put a limestone rock into a plastic jar and cover it with vinegar. Cover the jar and watch the bubbling of the calcium carbonate and also the disintegration of the rock over a few days.
SAFETY
To make sure that this experiment is safe, I need to make sure that I am wearing safety glasses. If HCL comes in contact with my eyes, I must wash it off immediately. If the chemical (Hydrochloric Acid) comes into contact with the surface, I must wash it off immediately. Also to make sure that the experiment is not done near the edge of the table, in case of the apparatus collapsing.
FAIR TEST
To ensure the experiment was fair the following requirements were made; the temperature of the solution should be kept constant. To avoid changes in temperature, the experiment was carried out away from the heaters. The surface areas of calcium carbonate (limestone) chips were kept roughly the same size. The weights of the chips were measured to be roughly about the same weight. The same equipments were used for every experiment done. All aspects were kept the same apart from concentration. The time, which the reaction was measured, was kept the same.
EQUIPMENT
> Measuring Cylinder
> Conical Flask
> Bowl
> Fresh Water
> Delivery Tube
> Rubber Bung
> Limestone Chips
> Hydrochloric Acid
> Beehive Shef
PLAN
The test tube will be placed in the test tube holder. The bowl will be filled with water, with a cylinder also filled with water, which will be placed in the middle of the bowl. The calcium carbonates chips will be weighed to approximately the same weight. The different amounts of concentration will be pressured using a cylinder and placed in the beaker. The calcium carbonate chips will be placed in the beaker.
The concentration solution will then be added to the test tube. Immediately after that the rubber bung will be placed in the test tube and the end of the delivery tube will be placed in the bowl inside the cylinder. The amount of carbon dioxide released will be noted at different intervals of times.
Here is an example of how my results table would look like:
% Concentration
Volume Of Carbon Dioxide Produced ml per Times/s
20
40
60
80
00
00
80
60
40
20
DIAGRAM
The diagram shows how the experiment looked like
METHOD
There will be five different set of concentration. There will be two sets of results to ensure accuracy; an average will be worked out.
The concentration solution should be added to the test tube containing the calcium chips. Immediately the bung will be placed in the test tube. As carbon dioxide is released, the water in the measuring cylinder should decrease. This process shall be carried out another four times using the different concentrations.
The experiment will then be corned out again for a second set of results from there a table can be worked out to show the average. To achieve a good range of results, we had to choose an appropriate interval for time. To close, and the results will be too similar. Too wide and the results won't be accurate enough.
RESULTS
TABLE 1: How the concentrations were made:
% Concentration
Hydrochloric Acid
Distilled Water
HCL
H2O
00
20ml
0ml
80
6ml
4ml
60
4ml
6ml
40
2ml
8ml
20
8ml
2ml
TABLE 2: The results obtained from the first experiment:
% Concentration
Volume Of Carbon Dioxide Produced ml per
Times /s
20
40
60
80
00
00
42
72
20
42
68
80
28
54
76
98
18
60
25
45
69
87
05
40
6
30
43
52
55
20
7
8
22
30
38
TABLE 3: The results obtained from the second experiment:
% Concentration
Volume Of Carbon Dioxide Produced 1ml per Times/s
20
40
60
80
00
00
48
72
20
45
70
80
30
62
84
08
18
60
20
42
68
86
90
40
0
24
36
44
52
20
4
6
20
32
40
TABLE 4: The average set of results:
% Concentration
Volume Of Carbon Dioxide Produced 1ml per Times/s
20
40
60
80
00
00
45
72
20
43.5
69
80
29
58
80
03
18
60
22.5
43.5
68.5
86.5
97.5
40
3
27
39.5
48
53.5
20
5.5
7
21
31
39
ANALYSIS
By looking at my results, I can tell that the more concentrated the solution of hydrochloric acid the faster the rate of reaction. This is because with a concentrated solution more particles are present and so there is an increased chance of collision. The rate of the reaction increases releasing more carbon dioxide.
The results, which were obtained from the experiments, were fairly accurate but not exact. The results were shown in a table like the sample shown below.
Concentration %
Volume Of Carbon Dioxide Produced 1ml per Times/s
20
40
00
45
72
80
29
58
The results were slightly inaccurate. This could be due to human error or the equipment used being faulty, whilst the experiment. Such as inaccurate measurements of the concentration could be a justification to my inaccurate results. The above figures also show that roughly a pattern/trend exists. As time doubled so did the amount of carbon dioxide produced and the amount of being released. The results, which I obtained, are reliable enough to come up with a conclusion because the results obtained and the predicted results are both similar. The results show the basic principle that if concentration increases so does the amount of carbon dioxide. This is predicted in my prediction.
CONCLUSION
At the beginning of this investigation I had predicted that by doubling the concentration of hydrochloric acid the rate of reaction would double. The results obtained showed that they were accurate. There were no incorrect results because I think that my experiment was good enough to get accurate and precise results. My method of using an upside down measuring cylinder was not a good method of carrying out this experiment. This is because the measuring cylinder had to be completely filled. This was very delicate. Therefore mistakes were made when ensuring that the measuring cylinder was fully completed. This could have been prevented. A gas syringe could have been used instead of a measuring cylinder. A gas syringe is used to identify the amount of gas present. It is more reliable and is a direct measure of carbon dioxide, which is released without the interference of Water.
My results seem really good enough because they show the basic principle. My results may not be exactly correct; however they are enough to come to a conclusion too. In order for limestone to react with hydrochloric acid is that:
> They must collide with each other.
> They must collide with enough energy.
A catalyst is a substance, which alters the rate of a chemical reaction without being used up. The mass of the catalyst remains unchanged throughout the reaction.
Improvements
If I were to do my investigation again, the following improvements would be made:
> The use of a gas syringe would have ensured that the gas bring released was measured accurately. (Although my method worked, a gas syringe would have given extremely precise and reliable results)
> To solve the problem of human error, I could have used colleges to help assist me with the experiment to ensure minimum error.
> The temperature of the room could have been noted down, to ensure it was in a controlled environment and so the temperature did not affect my results in any way.
> The experiments were done during different days, as there would not be enough time in one day. This may have affected my performance or the results.
> Not all the equipments were used again for each experiment, due to the fact it had to be handed in and done on a different day and would have caused confusion.
> Different type of equipment could have been used such as gas syringe instead of an upside down measuring cylinder.
EVALUATION
The method used for this experiment was not as reliable as I had expected. This was due to the way the measurements of the readings were made. This was because during the experiment an upside down measuring cylinder was used. The method could have been changed by using a gas syringe instead.
Gas Syringe
Beaker
Hydrochloric Acid
Calcium Carbonate chip
Concentration
The diagram shows how the experiment would have looked by using a Gas Syringe
The results have been slightly affected by the method. Overall the experiment worked out fairly well as the experiment results were reliable enough to support my predictions. The inaccurate results could have been caused by impurities in the water. Although distilled water was used. The distilled water could still have been contaminated. A more accurate scale could have been used to measure my calcium carbonate chips. During the experiment the Calcium Carbonate chips were weighed by using a weighing scale that measured in grams. A measuring cylinder, which measured in decimal places but still in grams, would have been sufficient.
In order to extend this to work I could have carried out the same experiment but also monitored the temperature of the concentration. All other factors were maintained which may have influenced my results. However to extend this experiment it would be interesting to carry out the experiment again using another factor also.
On the whole I would consider that my experiment was accurate enough to which a conclusion could be drawn. However the results were not as accurate as I had expected to make good judgements. To see if there were any differences or similarities. There are many reasons why this could have been. Although I could have had my concentrations of hydrochloric acid solution go up units of 10 instead of units of 20, also I should take more readings and averages. This would have been easier to see visible patterns or even changes in my results.
BIBLIOGRAPHY
* GCSE SCIENCE BOOK
- Authors: David Baylis, Graham Booth, Bob McDuell
* SCIENCE REVISION GUIDE
- Author: Richard Parsons
* LONSDALE REVISION GUIDE (GCSE SCIENCE)
- Author: Mary James
