Investigating the Rate of Reaction Between Marble Chips and Hydrochloric Acid
INVESTIGATING THE RATE OF REACTION BETWEEN MARBLE CHIPS AND HYDROCHLORIC ACID
* Introduction
This chemistry investigation was performed to investigate the rate of reaction (speed) between Marble Chips (Calcium Carbonate - CaCl ) and Hydrochloric Acid (HCL). In this investigation I want to find out whether the concentration of Hydrochloric Acid will affect the amount of Carbon Dioxide being given off.
The reaction rate would tell me how fast or slow a chemical reaction is and there are four things that could affect this greatly, they are: -
Concentration: An increase in concentration means there are more particles. More particles means there will be more collisions. This should increase the reaction rate.
Surface Area: when one of the reactants is solid, the reaction can only take place at the surface of the solid. Breaking the solid into smaller pieces will increase the surface area exposed to the other reactant. This should increase the reaction rate.
Temperature: since temperature is a measure of the motion of particles, increasing the temperature will cause the particles to move faster. When particles move faster, more collisions occur and the collisions are more violent. This should increase the reaction rate.
Catalysts: catalysts are substances that change the rate of a chemical reaction without being changed in the reaction. Catalysts are most often used to speed up a chemical reaction. They do so by changing the steps needed between reactants and the formation of the products. If the number of steps can be reduced, the reaction rate should increase.
Pressure: In terms of gas, increasing the pressure means the molecules are compressed together further. This means that there will be more collisions due to the lack of space for the molecules to move around.
* Reaction Rate
The Reaction Rate is often related to the Collision Theory, which describes the way temperature, concentration and surface area of the solid reactant affects the rate of reaction, by affecting collisions from particles. Particles react when they collide with sufficient energy. At a higher temperature collisions are more frequent and they also have more energy, both because particles are moving faster. At a higher concentration collisions are again more frequent, as there are more reactant particles in the liquid. Increase surface are of the solid again increases the frequency of collision between reacting particles, as the liquid reactant has greater contact with the solid one. The rate of reaction can also be increased by adding a catalyst, but there is not one of this used in this experiment.
Chemical reactions proceed at different speeds depending on the type of reacting substances and the type of chemical transformation. In general, reactions in which ions (electrically charged particles) combine or separate occur very quickly, while those in which covalent bonds are formed or broken are much slower. For a given set of reactants, the speed of the reaction will vary with the temperature or pressure on the experiment and the amounts of reactants used. Ordinarily the reaction will gradually slow down as the reactants become used up. In some cases the addition of a substance not itself a reactant, (the catalyst), accelerates a reaction that normally takes place at a very low rate.
* Concentration
Reaction rates can be increased if the concentration of reactants is raised. An increase in concentration produces more collisions. The chances of an effective collision goes up with the increase in concentration. Only experimental observation reveals the link between concentration and reaction rates.
* Safety
As with any investigations great care should be taken and the experiment should be undertaken in a sensible manner.
I will wear safety goggles throughout the investigation.
I will be careful so as not to spill any acid, but would ensure there was nothing near the experiment that could cause an accident or be damaged if an accident did occur.
We will assign one person to be in charge of the pure hydrochloric acid and one person to be in charge of the mixed solution of Hcl and marble chips, thus to prevent confusion as these are corrosive and harmful solutions.
In this experiment I will have to make sure I am careful with all glassware in case it breaks and if it does to make sure it is immediately cleaned up. As I will be using a conical flask its wide bottom gives a more secure base.
I will ensure that there is nothing ...
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We will assign one person to be in charge of the pure hydrochloric acid and one person to be in charge of the mixed solution of Hcl and marble chips, thus to prevent confusion as these are corrosive and harmful solutions.
In this experiment I will have to make sure I am careful with all glassware in case it breaks and if it does to make sure it is immediately cleaned up. As I will be using a conical flask its wide bottom gives a more secure base.
I will ensure that there is nothing else on my worktable obstructing the experiment.
I will ensure that I do not use too much acid, which could escape and spill when the temperature is raised. Also, I must be careful especially with the stronger concentration of acid because it will be corrosive so I must make sure I do not spill it on my hands or more especially in my eyes. One way to avoid this is to be extremely careful and wear safety goggles.
Once finished, I will put all my apparatus away and dispose of the Hcl solution properly.
* Fair Test
I will try to make sure that the marble chips will be of the same amount and mass - this is because I want to keep the chips as similar as possible throughout the experiment and ensure a fair test with the results in direct relationship to each other.
I will take readings at the same time intervals throughout the experiment i.e. I will take a time reading every fifteen seconds in all my experiments.
I will measure the hydrochloric acid accurately with a beaker and repeat each and every experiment I do three times.
I will ensure that the gas syringe is level otherwise this could affect how fast or slow it will slide backwards.
* Prediction
I predict that the higher the concentration of the acid, the faster the rate of reaction will be.
* Apparatus List
A conical flask - I chose this large enough to prevent spillage
A rubber bung - To prevent the gas expanding down the arm of the clamp
A gas syringe - to measure the amount of Co2 given off
A delivery tube - for connection to the gas syringe
A stand and clamp - to support the experiment
A stopwatch - to measure the time the reaction took accurately
Calcium carbonate chips
Hydrochloric acid - Different concentrations
* Method
When doing my experiments I will use the same procedure throughout. I will set out my equipment as shown in the diagram below:-
Throughout the experiment I was ready with the stopwatch, so that I started and stopped it immediately it was necessary to get accurate readings.
Once I have set up the apparatus I will measure out 50ml of acid in a measuring tube and then pour it into the conical flask. I will quickly place the chips into the acid, insert the bung in the top of the boiling tube and start the stopwatch. This must be done in as short a space of time as possible. From then on, I must take the reading of the volume in the gas syringe after a certain point is reached. I will use 6 different concentrations of hydrochloric acid and then recorded the amount of carbon dioxide in the gas syringe. I will accurately record these roughly in a table and write them up neatly later.
I will take into consideration that the speed with which I put in the marble chips, place in the bung and press the stop watch may well affect how well the experiment works.
Although these factors will affect the end result so long as they are kept constant throughout then it should not matter too much.
To get the best possible results I need to use the equipment in the best possible way, I could ensure that the syringe moves smoothly, so as not to get it stuck, which would affect my results. I will need three readings for each concentration and find the average to obtain more accurate results.
An important point to note is that I must use the right amount of acid and the best-sized amount of marbles. If I used about 4 chips for 4ml acid then too much gas will be produced. Then I would not be able to take correct readings. To overcome this problem I will test to see how many chips and what size will be the best to use. This would be preliminary work, a trial experiment that I will do before I start my proper one so I can set suitable parameters to use in my actual experiment. This would be beneficial to me because then I would be able to attain a range of measurements to an accurate level.
* Constants
Before I could begin recording measurements, I had to make sure that I had to determine the values of each of the constants in the experiment. From my preliminary wok (detailed above), I successfully concluded what of each I needed to obtain a range of suitable results.
The weight of the marble chips: I had to make this a constant because there was no practical way to measure the surface area. I set the parameters of the weight of the set of marble chips to b between 2.00g and 2.20g, but tried to keep it a near to 2.10g as possible.
The amount of marble chips used: This also was a constant to coincide with the weight. I kept the amount of marble chips to a constant of 7 per every experiment.
The time taken: I measured the time with a stop-watch and took readings at every 25 second intervals to satisfy the slower readings I received with the lower molars of acid and the much more erratic results I received with the higher molars of acid.
Amount of Reactant Used: I used 50 ml of Hcl for every experiment I did regardless of the concentration of the acid. It was all kept at a constant.
Bellow are the tables used to record the findings of each experiment. Each was repeated three times to ensure a fair test (next pages):-
0.1 Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
3
3
0
0.50
3
3
0
.15
3
3
0
.40
3
3
0
2.05
3
3
0
2.30
3
3
0
0.25 Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
0.50
2
.15
2
2
.40
2
2
3
2.05
3
2
3
2.30
3
2
3
0.5 Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
2
0.50
2
2
2
.15
3
4
2
.40
3
4
3
2.05
4
5
4
2.30
7
6
5
Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
9
4
6
0.50
7
4
5
.15
24
22
23
.40
35
31
34
2.05
44
42
46
2.30
57
51
59
.5 Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
3
9
2
0.50
24
29
23
.15
39
40
37
.40
55
55
52
2.05
72
69
67
2.30
88
82
85
2 Mols
Time (Seconds)
Amount Of Co2 Given Off (CM3)
1st Attempt
2nd Attempt
3rd Attempt
0.25
9
6
1
0.50
40
33
30
.15
61
50
51
.40
75
67
71
2.05
84
80
89
2.30
98
00
99
* Observations: As I did my experiment, I made some interesting observations, all of which had the potential to alter the results I received.
As we had no way of measuring the surface area, we had to rely on getting the weight of the marble chips accurate. My perimeters were set to a range between 2.00g and 2.20g. But even the smallest change could have had an effect on the results even if the change was very small.
We did the experiment on 2 different days. This would have meant the weather conditions were most likely different on those 2 days. It would have meant that the temperature varied on each day and also could have increased or decreased the rate of reaction. Also, some reactants are photogenic and can be affected by the light.
Luckily, the reactant we used was not a photogenic one, so we did not need to worry about that.
I noticed that we altered the experiment a little by the way we put the marble chips/acid into the conical flask. We started off putting the marble chips into the flask and then pouring the Hcl over them. And half way into the experiment, we rotated this process around and poured the Hcl in first. It could have had an effect on the rate of reaction as particles would move more vigorously if we poured the acid over the chips and vice-versa.
When putting the chips into the flask, a couple fell out, This was a problem if we had poured the acid in first and in some cases it was as we had lengthened the time it took to seal the conical flask with the rubber bung. Also, if some had fallen out, it would have been possible that we did not notice and when the missing marble chip(s) were found later, we could have dismissed these as coming from the fresh new batch of marble chips we had close by on the table.
Half way through the experiment, our gas syringe started to pick up moisture on its inside. This made the syringe very sticky and harder to push out and sometimes got stuck in its tube. Although we did begin to clean it later on, we could not be certain when it had started to pick up moisture and affect our results.
I noticed water droplets inside the conical flask when going to wash it after each experiment. Water could also have a affect on the rate of reaction and thus affect our results if it had contaminated the acid and marble chip mix.
On occasions, the conical flask was accidentally knocked by somebody's hand. This would have also affected my results if the bump had speeded up or in turn slowed down the rate of reaction.
We only attempted to weigh the amount of marble chips we had. We never actually monitored the appearance of each chip. If there were marble chips that were more rounded in shape, there would have been a change in surface area as a pose to the more angled and flat chips that we had.
Analyzing And Concluding
To ensure a fair test and for clarity, bellow is a table that shows my results as averages of the 3 attempts I did. To acquire the average result, I first totaled all the attempts then divided them by however many attempts we did, in this case, 3.
Time
(Seconds)
Amount Of Co2 Given Off (CM3)
0.1 mols
0.25 mols
0.5 mols
1 mols
1.5 mols
2 mols
0.25
2
.3
6.3
4.6
5.3
0.50
2
.3
2
5.3
25.3
34.3
.15
2
.6
3
23
38.6
54
.40
2
2.3
3.3
33.3
54
71
2.05
2
2.6
4.3
44
69.3
84.3
2.30
2
2.6
6
55.6
85
99
The table above shows an eventual rise of the amount of C02 being produced as the length of time increases. But there is an exception with the results recorded when performing the experiment with 0.1 mols. This is classed as an anomalous result and will be recognized later. For enhanced clarity, a graph has been constructed and displays the information on the table above:
The general trend here is that the longer the duration of the experiment, the greater the volume of CO2 will be (apart from he one anomalous result). The higher the concentration, the higher the rate of reaction s we can see from the table and graph. There is a steady build up from the lower concentrations, and this gradually rises steeper and steeper when we start going up through them.
We can understand why we have come to receive these findings as they as scientifically sound. Reaction rates can be increased if the concentration of reactants is raised. An increase in concentration produces more collisions. More particles will collide with each other because there are more of them, thus a far better chance of the reaction taking place faster. So, the chances of an effective collision goes up with the increase in concentration.
This also relates to my prediction:
"I predict that the higher the concentration of the acid, the faster the rate of reaction will be."
As explained above, because we were increasing the concentration of he reactant, there would have been more chance of the reaction occurring and at a faster speed. This can be proved by referring to the table and the graph. My prediction stated that the higher the rate of reaction, the faster the rate of reaction, and I can safely say that this prediction was correct in respect to the evidence obtained and the scientific knowledge displayed.
Evaluation
On the forefront, I believe that my experiment was a successful one because I was able to construct a sensible hypothesis, plan a safe and fair test and carry out the experiment to obtain suitable measurements that I could use to compare my prediction with. I was able to use my scientific knowledge to back up my results and use as evidence to re-enforce the procedure. I managed to prove my hypothesis was correct by doing this.
I feel that the reliability of the evidence does not meet high enough standards that would enable me to construct a firm conclusion. Based on the observations I made, there were many faults that could have dramatically altered all of the results I obtained. Whereas, I had sufficient evidence to support my hypothesis, I was not satisfied that the experiment I did was completely accurate. I did my utmost best to ensure a fair test, but some aspects were inadvertently overlooked and quite simply, there was not enough skill in some cases. I could have explored further and obtained more evidence if I had used a wider range of concentrations.
I could have crushed the marble chips into smaller pieces, thus altering the surface area, but at least I would have overcome the fault of having marble chips with angled edges and flat faces and more rounded sphere like ones which were different in terms of surface area and could have altered the accuracy of the results. We did the experiment of different days. This should not have been done as the weather conditions especially the temperature would have varied and as explained previously, temperature can have an affect on the rate of reaction.
I feel that the equipment we used was not satisfactory. We never once tested the delivery tube for damage. What if the tube did have a hole, however small in it? This would have affected our results. The gas syringe started to stick and became hard to slide. This also affected our results.
We did encounter two anomalous results. When we tested the 0.1 mol concentration of hydrochloric acid, we observed that the reaction produced 3cm3 of carbon dioxide. This was odd as the 0.25 mol concentration of Hcl just barely reached the 3cm3 mark, and this was a slow process with a stronger concentration. It could have been that he gas syringe had already started picking up moisture by the time we had begun our experiment with the 0.25 mol concentration and slowed the results down. Also, our 3rd attempt at the 0.1 mol concentration produced no results whatsoever, even though the previous two attempts had. This could have been due to many factors. Did we put in the right amount of marble chips? Did we make sure the conical flask was sealed properly? These could have meant that we would have received no results as we did here.
For future improvements to this experiment, I would recommend using far superior equipment for clearer results, a digital gas reader instead of the syringe that became sticky. To combat the temperature change, I would recommend that we do this experiment in a regulated room. We should most defiantly use a wider rang of concentrations. We should crush the marble chips into smaller pieces but ensure they still have a constant weight to we could overcome the problem of having chips with different surface areas. These improvisations can led to arriving at a firm and understandable conclusion that will undoubtedly be correct.
Arun Shukla (11MP) Candidate No: 1415
Thursday 10th January 2002 Center No: 12710 (Canons High School)
