Preliminary test
Before this experiment was taken place a Preliminary test was taken, to see if the apparatus was set properly, and there was no difficulties in the Preliminary test.
Resources used
During this experiment work much searched was used to find out more information about rates of reaction. The resources used were the library, the Internet, my teacher and books. I got the information about ‘the collision theory’ from the GCSE Chemistry Revision Guide. For the Internet I got help from .
Safety precautions
There are some serious health hazardous involved in conducting these experiments, but there are a few safety procedures that must be taken:
- In the case of accidents involving glass, all beakers and test tubes were kept away from the edge of the table. This way there was no risk of any accidental spillage.
- Hydrogen peroxide is dangerous and harmful (it has qualities such as bleaching) so laboratory coats and goggles were always worn throughout the experiment.
- When conducting hot liquids around, there should be no running around, so that no accidents would occur involving hot liquids. Special care was taken when transporting hot reactive metals, and when using corrosive metals in experiments.
- Extreme caution was exercised when dealing with the hydrochloric acid, as it is very corrosive. Plastic gloves were worn alongside large lab coats and goggles.
- In the temperature experiment, sulphuric acid was used. This substance is very strong acid that has a strong tendency to corrode. So special gloves that provide some protection were worn with goggles and large lab coats. Also the sulphuric acid was not directly placed over a Bunsen burner as it could set alight. So it was heated within a water bath filled with water.
- In the concentration experiment, extreme caution was exercised when dealing with the hydrochloric acid, as it is very corrosive. Plastic gloves were worn alongside large lab coats and goggles.
Apparatus used
During all the experiments many different types of apparatus were used. The following are the apparatus used:
- Conical flask.
- Hydrochloric acid (HCl)
- Rubber bung.
- Volume syringe.
- Calcium carbonate (Chalk)
- Water baths.
- Test tubes.
- Strips of magnesium (All should be the same size)
- Clamps (Stands)
- Thermometers.
- Bunsen burners.
- Sulphuric acid.
- Tripod stands.
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Sodium thoisulphate (Na2S2O3)
- Stop watch.
- Pieces of paper with an ‘X’ clearly marked upon it.
- Thistle funnel.
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Hydrogen peroxide (H2O2)
Factors that affect the rate of reaction
Surface Area
Planning
Aim
My aim in this part of the coursework is to discover whether or not the surface area of substances alongside the interaction with a unlike substance would alter the rate of reaction.
Apparatus list:
- A conical flask – I chose this large enough to prevent spillage
- Cotton wool – used over the conical flask for diffusion of certain gases
- Hydrochloric acid – with a fixed morality
- Calcium carbonate (Powder and chips)
- A stopwatch
- Electronic balance (2.d.p.)
- Mortar and pistol
Preliminary test
Before I had taken this experiment into exploitation, I carried out a preliminary test to see if the experiment was going to be a success or if any errors would arise during the experiment was into consideration. I had measured the acid using a measuring cylinder; this was not so accurate and could have been done more accurately by using a bulb and pet. This would have helped me keeping the place tidy and was guaranteed that I would not spill any acids as they can be harmful to naked skin. I also had to put the cotton wool in the neck of the conical flask as soon as possible, which I might have been unable to do. This may give me an error in my results. I had set up the apparatus as it has been shown below and there were no such major errors.
The apparatus will be set as the diagram below:
Figure 1a
Fair test
Without neutralising variables the experiment would not be a fair test and it will also affect the results. Below is a list of variables that will be neutralised to make it a fair test:
- Apparatus that produce heat would not be close to the temperature. The experiment will be conducted within a short period of time to reduce the possibility of any variable in temperature.
- The concentration of any reactants will remain the same in order to conduct a fair test.
- I will try to make sure that the marble chips will be of the same size, amount and mass. This is taken into consideration, as I want to keep the chips as similar as possible throughout the experiment and hopefully be a fair test with the results in direct relationship to each other. If these varied then I would expect the result to be inaccurate and so ruin my experiment.
Prediction
It is believed that the increase in the surface area of a substance would result in the increase in the rate of reactivity. The more concentrated the substance the faster the reaction will be. The more surface will allow the particles around to have more collisions.
Small Surface Area Large Surface Area
Also, the smaller the marble chips are, the surface area will be increased and so I would expect the reaction rate to be increased.
Hypothesis
It can be deduced that the more area available for a reactant would result in an increase in the rate of reaction because there is more space for reactive particles to work.
This experiment is based on the following equation
CaCO3 (s) + 2HCl (aq) CaCl2 (aq) + CO2 (g) + H2O (l)
Calcium Carbonate + Hydrochloric Acid Calcium Chloride + Carbon dioxide + Water
Method
- A fixed amount of Hydrochloric acid is filled into the conical flask.
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The calcium carbonate (CaCO3) is crushed into pieces into a fine powder. This was done by a mortar and pistol.
- The powder is measured until the right mass is achieved. In the first segment it is 25.30 grams.
- 100ml of hydrochloric acid (1 molar) is added into the conical flask.
- The conical flask was now placed on the electrical scale and it was made sure that the readings were 0; I used the TARE facilities to do this.
- The chippings were taken and gently poured into the acid in the conical flask and simultaneously the stopwatch was started.
- Immediately the cotton wool was placed on the neck of the conical flask.
- This should be done in as short a space of time as possible.
- Throughout the experiment I was ready with a stopwatch, so that I started and stopped it immediately it was necessary to get accurate readings.
- Every minute the results were recorded by the actual mass on the scale. It was recorded for one minute at an interval for 10 minutes.
- The same steps are repeated although some of the tests involved the Calcium carbonate being Chips whilst the other tests involved the calcium carbonate existing the form of powder. However when the powder form was required the calcium carbonate had to be hammered. The same preparation was done for the calcium carbonate – chips form, but instead of hammering the calcium carbonate to make power they we’re made into small blocks (chips), that were tried to be kept in the small shape as possible.
Results
The following tables show the results that were obtained by doing both experiments (calcium carbonate chips and powder):
Table 3a
Chips - Calcium carbonate (CaCO3)
Powder - Calcium carbonate (CaCO3)
These results are shown the graph 2a on the next page:
Factors affecting the rate of reaction
Temperature
Planning
Aim
My aim in this part of the coursework is to find out the rate of reaction of chemical substances, whether or not the rate of reaction is affected by the intensity in temperature.
Apparatus listed
- Sulphuric Acid
- 10-11 Magnesium Strips – should be scrapped thoroughly and should be made all the same size.
- Tripod – to place the water bath on.
- Water bath – contains water with a test tube.
- Test tube – needed to place the sulphuric acid and the magnesium strip, for the reaction to take place.
- Bunsen burner- needed to keep the temperature constant.
- Stop watch
- Bulb and pipette – to measure the amount of sulphuric acid to be used.
The apparatus will be set as the diagram below:
Figure 1b
Fair test
Without neutralising variables the experiment would not be a fair test and it will also affect the results. Below is a list of variables that will be neutralised to make it a fair test:
The surface area will remain the same.
- The concentration of any reactants will stay to make this investigation a fair test.
This experiment is based on the following formula
Mg (s) + H2SO4 (aq) MgSO4 (aq) + H2
Magnesium + Sulphuric Acid Magnesium Sulphate + Hydrogen
Variables
There many variables that can be changed in some ways to effect the reaction, some of which are listed below:
- Volume of Sulphuric Acid
- Concentration of Sulphuric Acid
- Initial temperature of Sulphuric Acid
- Purity of Magnesium
- The extent of oxidation on the surface of the magnesium
- Additions of catalyst
- Size of container
- Temperature of surrounding environment
- Pressure of the conical flask.
- Height of thermometer above the base of the test tube.
Explaining the variables
In higher concentration solutions, particles are close together. They have a greater chance of colliding, this is because there are more collisions therefore the rate of reaction is greater. This is explained thoroughly in the ‘Introduction’ of this coursework.
Catalysts can affect the rate of reaction. Catalysts can speed up the reaction. Only very minute qualities of catalyst are needed to make a dramatic change in the rate of reaction. When the catalyst is added the reaction reacts in a different way as it usually does. When adding extra catalyst, the rate of reaction will change but only up to a certain extent, after that it will have no difference.
There are two methods in which the catalyst works. One is adsorption and the second is by making intermediate compounds.
Adsorption is when a molecule sticks onto the surface of the catalyst but it is not absorbed at the same time. Intermediate compounds are when many catalysts, and enzymes work together to form an intermediate compound. A new compound is made and this is very unstable, this unstable compound is broken down and it releases many other new compounds and the original catalyst.
Prediction
My prediction in this experiment is that when the temperature is low, the magnesium strips will react slower. But when we increase the temperature we will notice that the magnesium strips will react a lot faster. When the temperature is increased the particles move faster. So if they move faster there will be more collisions between the particles.
Cold Hot
For example
When the temperature is at 300c the reaction to the magnesium strips will be fast. But when the temperature is at 800c the reaction to the magnesium strips will be much faster that the first one.
I will clarify my prediction in my hypothesis.
Hypothesis
My prediction is based upon the collision theory that starts more collision equal a faster rate of reaction. When heat is applied to a reactive particle, the particles absorb the heat energy and this breaks the bonds between them. This causes them to move faster; therefore there is an increase to the reaction of the magnesium strips when the heat is applied.
For example: some very dilute acid is taken and an alkali in a solution, now it is imagined that all the particles are bouncing around at random, this can be appreciated for a reaction to occur. The acid particles must hit the alkal particles before any reaction that is visible to the eye can take place. As the acid is very dilute many of these collisions will be with harmless water molecules, this does not play the part of the reaction. Therefore it may take a while for the collisions to take place. On the other hand if the concentration of the acid is increased, there will be fewer molecules to get in the way, so there are more useful collisions per second, therefore the reaction will happen at a much faster rate, this increases the temperature.
If the experiment was to do with gases then to change them into a high concentration to obtain an increase in temperature, the gases would be squashed, hence now the particles would have less space to move around, and therefore the concentration is high. This also will increase the temperature.
Method
- Firstly all the apparatus was gathered.
- A test tube was filled with 0.1 mole of sulphur acid.
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The test tube then was placed in the fridge until its temperature falls down to 100c.
- The magnesium strip that will be used will be scrapped to ensure that there is no magnesium oxide. (We took the magnesium oxide off because it is the coat of the magnesium strip and if the coat stayed on the magnesium strip will not react.)
- A one-centimetre piece of magnesium strip is added to the acid.
- As soon as the magnesium strip is added the stopwatch is started.
- When the magnesium strip is dissolved the stopwatch is stopped.
- Three trails are taken to obtain accurate results via an average.
- The results are recorded on a table.
- The test of suspended in a water bath of plain water.
- Then we light the Bunsen burner.
- Then we get the test tube out the fridge and check the temperature.
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When the temperature is exact 200c, we add a magnesium strip to the acid.
- When the magnesium strip is dissolved then we stop the stopwatch.
- The result is recorded on a table.
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We do the same every time, but we increase the temperature by 200c.
-
We record the results up to 1000c.
Results
The table shown on the next page shows the results that are based on the temperature experiment:
Table 3b
This data is shown on graph 2b on the next page:
Factors affecting the rate of reaction
Concentration
Planning
Aim
My aim in this part of the coursework is to find whether or not the rate of reaction increases when the concentration of a reaction is increased.
I must produce a piece of coursework investigating the rates of reaction, and the effect different chances have on them. The arte of reaction is the arte of loss of a reactant or the rate of formation of a product during a chemical reaction. It is measured by dividing 1 by the time taken for the reaction to take place. There is five factors which affect the rate of a reaction, according to the collision theory of reacting particles: temperature, concentration, pressure, surface area, catalyst and concentration. In this part of the coursework I will be scrutinizing the effect of concentration.
Apparatus listed:
- Hydrochloric acid (40 ml, need 10 ml in each conical flask)
- Solution of Sodium thiosulphate
- Water (Concentration will be fixed)
- 4 conical flasks (the same size)
- Square pieces of paper with and ‘X’ marked on it, with marker.
- Stop watch.
The apparatus will be set as the diagram below:
Figure 1c
Fair test
Without neutralising variables the experiment would not be a fair test and it will also affect the results. Below is a list of variables that will be neutralised to make it a fair test:
- Apparatus that produce heat would not be close to the temperature. The experiment will be conducted within a short period of time to reduce the possibility of any variability in temperature.
- Both substances within the reaction were liquids so to control the surface area it will be very difficult.
- No catalysts would be used.
- I will use the same standard of time judged when the ‘X’ has disappeared.
- I will make sure that the cylinders of HCl and Sodium thiosulphate will not mix up.
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The fixed amount of Na2S2O3 and water is added each time.
- All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful.
Prediction
It can be deduced that when the amount of reactive particles is increased the more chance there is of collision therefore resulting in an increasing rate of reaction. There will be more particles knocking between the water molecules, which makes more collisions. The prediction is elaborated and entirely explained in the hypothesis on the next page:
Hypothesis
It is believed that the higher the concentration of a reactive substance the faster the rate of reaction would be. This is because a high concentration means there are a lot of reactive particles. So the more reactive particles there are the higher the chance of collisions in a smaller period of time therefore the reaction would be faster. If a low concentration were used in the reaction there would be very few reactive particles to complete the entire reaction therefore resulting in a very slow rate of reaction.
The experiment is based on following equation
Na2S2O3 (aq) + 2HCl (aq) 2NaCl (aq) + SO2 (g) + H2O (l) + S (s)
Sodium thiosulphate + Hydrochloric Acid Sodium Chloride + Sulphur Oxide + Water + Sulphur
Method
- 10 ml of hydrochloric acid is calculated.
- 40 ml of sodium thiosulphate is added to a conical flask.
- 10ml of water is added to the conical flask.
- When the reaction begins the stopwatch is started.
- When the white precipitate has formed completely so that it prevents vision of the “X” the stopwatch is stopped.
- The time is recorded.
- The concentration of the sodium thiosulphate is the decreased by 10 ml but the volume of hydrochloric acid will stay the same, 10ml, as it has a fixed concentration.
- The same steps are required however each time the concentration of sodium thiosulphate is decreased by 10ml and the volume of water is increased by 10 ml.
- After four times of sodium thiosulphate being decreased.
- This is done four times with the volume of sodium thiosulphate decreasing by 10 ml from 40 ml to 10 ml. And increasing of water by 10 ml from 10ml to 40 ml.
- The result were noticed and recorded. This was to show how long it took for the ‘X’ to disappear.
Results
The results below for the experiment with 10 ml of 2 molar sodium thiosulphate have been represented upon the table and graph below:
Table 3c
This data is shown on the graph 2c on the next page:
Factors that affect the rate of reaction
Catalyst
Planning
Aim
My aim in this part of the coursework is to find out whether or not the rate of reaction is affected by the interaction of a catalyst.
The experiment is based upon the formula below:
Hydrogen peroxide water + oxygen
Catalyst
2H2O2 (aq) H2O (l) + O2 (g)
Hydrogen Peroxide is a clear, colourless liquid with the formula H2O2. The hydrogen peroxide decomposes when exposed to light. The amount of oxygen produced with a catalyst and with out a catalyst is measured.
Apparatus listed:
- Hydrogen Peroxide Solution
- Potato Chippings – cut all the same size – used as a catalyst.
- Test tubes
- Test tube clamp stands – to hold the test tube in position
- Stopwatch
- Delivery tube (this is used to transfer the oxygen gas bubbles form one test tube to the other, so it is easier to count them and record data.)
The apparatus will be set as the diagram below:
Figure 1d
Fair test
Without neutralising variables the experiment would not be a fair test and it will also affect the results. Below is a list of variables that will be neutralised to make it a fair test:
- Apparatus that produce heat would not be close to the temperature. The experiment will be conducted within a short period of time to reduce the possibility of any variability in temperature.
- The concentration of any reactants will remain the same in order to conduct a fair test.
Prediction
It is predicted that a reaction that occurs with a catalyst present would result in a faster rate of reaction than an identical reaction that does not have a catalyst present. I predict my graph with both, with catalyst and without catalyst, will look like the following:
Without Catalyst
With Catalyst
This theory has been thoroughly thought out and explained below in the hypothesis:
Hypothesis
It is believed that if a reaction takes place with a catalyst present the reaction would be much faster. This is because catalysts are enzymes, which decompose material. This decomposition would lead to a larger surface area being exposed to a reactive substance therefore resulting in a faster rate of reaction.
This experiment is based upon the formula below:
Hydrogen peroxide Catalyst Water (Potato Chips) + Oxygen
2 H2O2 (l) Catalyst 2 H2O (l) + O2 (g)
The hydrogen peroxide decomposes when exposed to light. The amount of oxygen produced with a catalyst and without a catalyst is measured.
Method
- A test tube is placed upon a work surface in a test tube stand, alongside with cut potato chips (they should all be the same size).
- The hydrogen peroxide is then released into the conical flask.
- We now have in hand the potato chips. As soon as they are unconstrained into the conical flask the stopwatch is started, and also the conical is plugged with cotton wool to stop any liquid splashing out.
- Every two-minute the amount of oxygen bubbles produced are read and readings are recorded.
- The same steps are repeated only in the second segment there is no catalyst present. It is only done with the hydrogen peroxide at the same temperature as I used in the experiment in which the catalyst was present.
- The amount of oxygen bubbles produced every two minutes without catalyst present was also recorded.
- These results are shown in the two tables below:
Results
The results of both parts of the experiment have been shown on the next page. The first table shows results for the reaction with catalyst, and the other shows the reaction without catalyst:
Table 3d
With catalyst
Without catalyst
These results are shown on graph 2d on the next page:
Assessment
Does catalyst affect the rate of reaction?
After conducting two experiments with a catalyst and without a catalyst we can observe the results to see if a catalyst will speed up the reaction. From looking at the results from the experiment we can conclude that the reaction proved faster with the catalyst. We can see this because after two minutes, with a catalyst present, the volume of oxygen produced was already 12cm3. However, after two minutes without catalyst present only 3.5 cm3 of oxygen was produced.
We can also see that catalyst increases the reaction because in the 10th minute, with a catalyst present, 44 cm3 of oxygen was produced. When there is not a catalyst only 17.3cm3 of oxygen was produced. So by these statistics we can say that when there is not a catalyst the reaction produces some oxygen but very slowly.
During the experiment there were some anomalous results. This means that the results did not fit the line of best fit.
Does concentration affect the rate of reaction?
After conducting both experiments using higher concentrates solution and lower concentrated solution we can observe if concentration affects the rate of reaction. By looking at the results of this experiment we can conclude that the more the sodium thiosulphate and the Hydrochloric Acid at a stable concentration the faster the reaction will be. We can prove this because when a molar solution of 10ml sodium thiosulphate was used, it took 194.000 seconds for the cross on the paper to disappear.
However, when 40 ml of solution was being used the reaction took for times shorter 42.830 seconds. When a 40 ml of sodium thiosulphate was being used the cross disappeared in only seconds but when using a 40 ml solution it took a longer time. Another experiment was carried out carried out by using water at a varied concentration, as when the sodium thiosulphate was increased the water was decreased and when the sodium thiosulphate was decreased the water concentration was increased, and keeping the HCl constant. By looking at the result we can see that when there is less concentration of water and more of sodium thiosulphate it took up a short time for the cross to disappear and by using more concentration of water and less of sodium thiosulphate the reaction took a longer time for the ‘X’ to disappear. So, by using the result we can conclude that the less concentrated the solution of sodium thiosulphate the slower the reaction will be and the more concentrated solution the faster the reaction will be.
Does surface area affect the rate of reaction?
After conducting both experiments using calcium carbonate in chips form and in powder form we can then analysis the result to see if the surface are will affect the reaction. By looking at the result we can say that when the calcium carbonate is broken down into powder form, the reaction will be faster than in chips form. We can see from the results that calcium carbonate in powder form had a higher weight loss in the first 10 minutes than the calcium carbonate chips. We can see this by looking at Table 3a. For example, we can see that in the 5th minute when using calcium carbonate chips the weight loss is 1.80 g and in the 5th minute when using calcium carbonate powder form the weight loss is 1.87 g. by looking at this result we can see that in the powder form there is a higher weight loss that the calcium carbonate chips form.
Does temperature affect the rate of reaction?
Once the experiment was completed the results were gathered and analysed to see if the temperature affects the rate of reaction. By observing the results we can say that the higher the temperature the faster it took for the magnesium ribbon to disappear. When the temperature was 100c it took 60 seconds for the magnesium strip to disappear.
When the temperature was 800c it only took a much faster time of 37 seconds. We can conclude the lower the temperature the slower the reaction.
Conclusion
All my results supported my hypothesis and prediction very well. And my final conclusion has been graded.
From the results I have concluded that when the temperature is low, magnesium will react slower. But when we increase the temperature we will notice that magnesium will react faster.
I also located that as the temperature was rising during the investigation, the time that was recorded kept on increasing.
Convection takes place in the reaction. It is the progress of particles. Sulphuric acid convection current affects water.
The more the water there is the more the conventional current there is between the particles. Possibilities occur by the reaction becoming faster as well as slower.
When heat is brought near the solution of the magnesium the convention moves all the particles.
This should be kept in mind that before the magnesium strip is put in the solution it should be scraped off. Magnesium only reacts with oxygen, which forms magnesium oxide:
2Mg + O2 2MgO
A thin white layer will occur on top of the magnesium strip when it is reacted with oxygen in air. It will prevent the reaction-taking place. Therefore there is need for it to be scraped off.
The internal energy in chemical reaction is called enthalpy. This is the prescription of energy delivered by a thermodynamic system that can be exchanged between itself and the environment, we take the temperature of the acid and the chemical compound would not take up the internal energy.
The results for the catalyst reaction shows that the catalyst does affect the rate of chemical reaction by speeding the reaction up but it did not change until the end of the reaction. I had made two graphs, by looking at both pf the graphs I realised that the experiment with catalyst is speeding up the reaction but at a certain period of time the catalyst no longer works. The reaction was quite slow.
The enzymes in the potato are the catalyst in the reaction. It is an example of an enzyme. Enzymes are proteins, which act as biological catalysts. The enzymes work best at blood temperature, i.e. 370c.
The temperature could affect how the enzymes in the potato are behaving. If the reaction works with a warm potato and warm hydrogen peroxide neither the temperature of the potato was taken into consideration while conducting the experiment. So this could later affect the result.
From the result of the concentration of acid, I conclude that the concentration does affect the rate of reaction. So now I can say that:
- A high concentration substance leads to a high rate of reaction.
- A low concentration substance leads to a low rate of reaction.
- A substance of high concentration has more particles to react with.
- In a weaker solution there are a fewer particles to react. In concentrated solution there is a chance of molecules coming in contact with each other, this takes us on the collision theory.
From the graphs the below things were noticed about the final results:
- The reaction with 2 molar concentrations is faster than 0.5 molar.
- The average rate in 2 molar was twice the average rate on 0.5molar.
The following points should be taken in to consideration while conducting the experiment:
- Every single size of the particle is not the same.
- When making chips, there is less surface are.
- Every single particle of the powder is not exposed at the same time with a sulphuric acid.
It has been proved that the surface area does affect the rate of chemical reaction. The result in graphs shows that a faster reaction took place when calcium carbonate chips were in powdered form. This is because the smaller the pieces of the chips, the more surface area is exposed. Whereas, the larger pieces have less surface area exposed and this produces a slower reaction. As I mentioned earlier an increase in surface area causes an increase in the rate of the reaction. When one of the reactants is a solid into smaller pieces, the reaction must take place on the surface area of the solid.
By breaking up the solid into smaller pieces, the surface area is increases, giving greater area for the collision to take place. This explains why mixtures of coal, dust and air can cause explosions.
The carbon dioxide is a heavy gas and the moment it is put in the acid, it settles at calcium carbonate.
It is important to take consideration that the syringe is more useful gas rather than collecting gas in the beaker. This is due to the fact that the carbon dioxide gas when put into the aqueous solution of hydrochloric acid, there is a possibility that some of the gas might mix with the acid and form totally different ions called the hydrogen carbonate ions. These ions could not affect the rate of reaction. The reaction that is formed with the ions is:
CO + H HCO3
Evaluation
Evaluation on the surface area experiment
For this experiment it was predicted that when the experiment was done in powder form to increase the surface area the reaction would go faster. When the experiment was done with chip form to decrease the area the reaction will go slower. This was felt that because when the surface area is larger the particles would be able to move around freely and have more collisions. By looking at the graphs it shows the prediction is correct.
Not all of the results were correct. When the solution was 1 molar in powder from the result was not in the line of best fit.
However, the rest of the result proved to be correct and prove successful.
Improvements, which could have been made:
- Using more grams of chip and powder form of calcium carbonate.
- Using more molars of hydrochloric acid.
- Use wooden clamps with better grip to prevent thermometers from slipping.
- Use more accurate thermometer so that more accurate readings can be read.
Evaluation on the concentration experiment:
For this experiment it was predicted that the more concentrated the solution the slower. This was felt because with more solution there will be more particles knocking between water molecules which make more collisions.
With comparing both line graphs with a higher and lower concentration solution we can see that the prediction was right.
All results were reliable and were a successful experiment.
Improvements that could have been made were:
- With more time three trails could be carried out to get more accurate results.
- We could have used a 3 molar solution and a 0.1 molar solution.
- Make sure that the concentrations of acid were as they started so that we know that the results were as accurate as we thought.
Evaluation on the catalyst experiment:
For this experiment it was predicted that when a catalyst is present the speed of the reaction would be faster. Also, with a catalyst it was felt that much more oxygen would be produced. By looking at the results in graph form we can say that the predicted was correct.
However, not all the results are correct and don’t fit in the line of best fit. We can see that the results when a catalyst were reliable and did fit the line of best fit.
For the line graph without a catalyst present there were a lot of results that did not fit in the line of best fit. We can say that these results are anomalous and wrong. The results may have been wrong because the temperature may have changed or some gas may have escaped when going in the syringe.
Improvements, which could have been made:
- A pour catalyst could have been used.
- An oxygen detector could have been used to get more accurate results.
- More trails could have been done to get more accurate results.
- Insulate the test-tube, which would prevent heat form being dissipated to the surrounding and allowing the thermometer to get a more accurate reading of the heat produced by the reaction.
Evaluation on the temperature experiment:
For this experiment it was predicted that when the temperature would increase so would the rate of reaction. This was felt because when the temperature increases the particles move faster. By looking at the line results we can see that the line graph as the temperature increase the time taken for the magnesium ribbon to disappear decrease. This shows the prediction is correct. However, not all results are correct. When the temperature was 300c and 500c the time taken increased. This may have been due to many reasons.
Improvements, which could have been made:
- Could have started with a lower temperature.
- Use pure magnesium filings to increase surface area and increate the rate of reaction, which should give a greater variation between concentration; this will give a better result for the temperature experiment.
- Make sure that non-oxidised magnesium strips are used to give more accurate results.
- Control the temperature of the surrounding by encasing each experiment to prevent any changes in temperature at the start of the reaction to the end of the reaction form affecting the experiment.
Extensions that can be carried out after the investigation
After this experiment was done, I had realised that I could have taken the following points under consideration to make it a better investigation:
- More concentrations of acid could be used to see if they have similar affects on the temperature rise.
- Different substances could be reacted to see if they behave similarly.
- More repeats could have been carried out to qualify the findings. These could be done under different conditions to see how the reactions react under a colder or hotter environment.
Inaccurate results
During the experiment we can see that many results were wrong and did not fit the line of best fit. There are some reasons to why they may have gone wrong:
- When doing the experiments there is an internal energy that may have affected the results. This is known as Enthalpy. When we heat the sulphuric acid we measure the temperature not the internal energy. It is very hard to control and measure the Enthalpy. The internal energy measures the amount of heat present inside the chemical compound.
- When doing the temperature experiment convection in the sulphuric acid affects the water current. There is a chance that the reaction could go faster or slower.
- When doing the surface area experiment the sizes of the calcium carbonate chips were not the same. This may have affected the results.