To achieve the most accurate of results possible I will use all sufficient equipment and data.
For my prediction, that the higher the concentration, the faster the reaction rate, I will use pre-test results to help with my evaluation before I start my investigation.
Before I started my investigation, I did a pre-test experiment that helped me to reach my prediction.
My experiment consisted of:
- 2 Beakers
- A small amount of Calcium Carbonate in each
- Beaker A being filled with 0.5M of HCl.
- Beaker B being filled with 1M of HCl.
Beaker A had a lower concentration of HCl, which will make the particles collide but over a longer period of time compared to beaker B which had a higher concentration.
Beaker B had a higher concentration, which means that there are a greater number of particles to collide with each other, which will reduce the time taken for the Calcium Carbonate pieces to react.
My prediction was also supported by the scientific theory, which is; an explanation supported by tests and accepted by a general consensus of scientists, which, in this case were my fellow classmates. We all agreed that, the higher the concentration becomes, the faster the time will be that the Calcium Carbonate pieces takes to react.
For My investigation into whether the concentration level of HCl will affect the reaction rate of Calcium Carbonate I will use 2g of Calcium Carbonate in 30cm3 of Hydrochloric Acid (HCl) to collect 40cm3 of Carbon Dioxide.
I will change the concentration of the HCl to test my prediction.
I will use:
0.5M of HCl,
0.75M of HCl,
1.0M of HCl,
1.5M of HCl
And 2.0M of HCl.
Using 5 different concentrations will help test my prediction and
using my pre-test, I predict that, as shown, as the concentration gets higher, the reaction rate will get faster.
The factors that I will keep the same throughout the experiment are:
The mass of the Calcium Carbonate, The volume of acid for each test respectively and the most important of the variables that are being used in this investigation, the volume of the carbon dioxide gas for collection.
The materials and equipment that I will need for my experiment consist of:
- 10g of Calcium Carbonate pieces, which will be used over the course of 5 separate experiments, using 2g in each experiment to with different Molarity.
- 0.5M, 0.75M, 1.0M, 1.5M and 2.0M of Hydrochloric Acid (HCl) to test the rate of reaction.
- A Conical flask that will hold the acid and Calcium Carbonate whilst the Carbon dioxide is collected and the experiment is in progress.
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A gas syringe to collect 40cm3 of the Carbon dioxide and it will give me greater accuracy.
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A timer/stopwatch to record the time taken to collect the 40cm3 of gas.
- A clamp to hold the gas syringe in place.
- A clamp stand to hold the gas syringe and the clamp in place.
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A measuring cylinder to measure out the 30cm3 of HCl for each experiment and each Molarity.
My method for this experiment is:
- Set up the apparatus using all the equipment stated above.
- Weigh out the 2g of Calcium Carbonate using electronic scales to achieve precision.
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Measure out 30cm3 of 0.5M of HCl for the first experiment using the measuring cylinder.
- Pour the measured HCl into the conical flask containing the Calcium Carbonate pieces.
- Place gas syringe stopper over the opening of the conical flask.
- Start timer once top of conical flask is covered.
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Stop timer once gas collection level reaches 40cm3 of Carbon dioxide.
- Record time and remove stopper from conical flask.
- Once result has been recorded, wash conical flask thoroughly.
- Repeat test using other Molarities of 0.75M, 1.0M, 1.5M and 2.0M.
A diagram of my experiment showing all equipment used can be clearly shown below:
Appropriate safety issues must be adhered during the experiment and these may include:
- Any Long hair must be tied back.
- Do not sit down whilst experiment is in progress.
- Ties must be tucked in.
- Handle all apparatus with care.
- Acid is corrosive so extreme care must be taken.
- Safety goggles.
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If spilled wash with plenty of H2O.
This experiment must be kept as fair as possible and a few examples of how to keep this experiment fair are:
- Keep the same mass of Calcium carbonate the same to achieve sufficient results.
- Use the same volume of HCl throughout to also achieve sufficient results.
- Use the same method throughout the experiment.
- Results must be recorded efficiently.
My results have been represented in a table and will later be put into a graph.
A third test was needed for the 0.5M oh HCl because the results were vastly different and a third test would help even out my results. From doing a third test, I have shown that TEST 1 gave me an anomalous result.
These results are also represented in a scatter graph as attached.
To calculate the rate of the reaction you use the amount of Co2 collected divided by the average time.
To work out the average you use the times taken divided by the amount of times taken.
(For 0.5M, the results that will be used will be TEST 2 and TEST 3 because TEST 1 had an anomalous result).
These results for each concentration can be represented in a table as shown below:
These results show at what rate that the Calcium Carbonate reacted at.
My evaluation of this investigation is the following.
My results proved that my prediction was right and I believe that my experiment was successful because of the correlation and the similarities in the results.
My average times were similar to the times that were recorded and showed a strong correlation on my scatter graph because of the trend and correspondence.
In my first test there was an anomalous result that was tested again and found that there was a problem with the recording of the data.
There can be errors when an investigation like this is taking place and a sample of these errors are stated below:
- There may have been a human error of timing, which therefore may give an unfair result because of the precision of the timing or the time taken to stop the stopwatch.
- The precision of the equipment may not be to a high standard, which in turn, can give false results or an untrue result.
- The concentration may not be correct and the concentration that was used was not the Molarity that was stated on the label or as mixed with the water.
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Gas lost from the conical flask when stopper is placed, releasing gas means a longer period of time for the gas syringe to fill up with the Co2.
- Different surface areas of the Calcium Carbonate pieces could also affect the final results as, the larger the surface, the faster or slower it takes for the Calcium carbonate to react.
If I were to do the investigation again, I would choose different concentrations variables or different weight variables of the Calcium carbonate.
Another change that I could make could be the measure of the volume of gas given off at different intervals.