Step7: Repeat Steps2-6 two more times, recording the volume of gas collected each time.
Step8: Repeat Steps2-7 but with acid concentration 2.0M
Step9: Repeat Steps2-7 but with acid concentration 1.5M
Step10: Repeat Steps2-7 but with acid concentration 1.0M
Step11: Repeat Steps2-7 but with acid concentration 0.5M
My results will be collected and recorded in a table similar to this:
Fair Test
To make my experiment a fair test, I would use the same apparatus for every test. However, I will change the connical flask used after each test. This is to make sure that acid of another concentration does not interfere with an investigation. I have to keep the temperature of my surroundings, the weight of the calcium carbonate, the volume of acid and the time constant in all the experiments only changing the concentration of the acid.
Reliability
To make my experiment as reliable as possible I will do the experiments three times over so that I will have an expected trend. To make this experiment precise I will make sure that the pan balance’s reading is measured to accuracy. This is because the pan balance fluctuates a lot. I will have to find out the accuracy of the pan balance by measuring the weight of a nail four times find the difference between the biggest weight and the smallest weight the pan balance gives me. Therefore, any results I have will be accurate to that that number. I will carry out this experiment later on in the plan. I will also make sure that when I am measuring the volume of the acid in the test tube, I take the measurement of the lower meniscus.
Safety
For this experiment to be carried out safely, I need to be careful as I will be using a corrosive liquid. I will wear hand gloves to protect my hands from direct contact of hydrochloric acid. In addition, if there is contact with the body at anytime, I will splash a lot of cold water on the affected part immediately.
I have to keep all the variables the same except the concentration of acid which is my input variable. Different factors can interfere with the rate of reaction; I therefore have to keep those factors constant in all the experiments. For instance the temperature is the average kinetic energy of particles, the higher the temperature, the more the average kinetic energy increases , therefore the particles have more energy to move about, so there is more chance that they will collide successfully with each other, more carbon dioxide gas is produced and collected, therefore a higher rate of reaction. I am basing this on the fact that carbon dioxide is a heavy gas and so can be easily collected using a gas syringe. To control the temperature I am going to perform my experiments under a ceiling fan, this will ensure that any air particles that are heated up due to the course of my experiment will be removed from that area and will be replaced with cooler air.
This will make the temperature of that area fairly constant so as not to interfere with my experiment. I also have to keep the weight of calcium carbonate that I will be using constant, because the more calcium carbonate there are, the more particles of calcium carbonate there are to collide with, therefore more carbon dioxide is produced, therefore a faster rate of reaction. To keep this variable constant, I will measure every amount of calcium carbonate I will be using on the top pan balance and make sure that they are of the same weight. I also have to make sure that the volume of acid is the same for all the experiments, even though there are different concentrations. This is because if I alter the volume any time during my experiment, it would mean that concentration would be inaccurate because concentration deals with the same volume. To keep the volume the same I have to measure the volume of hydrochloric acid I am going to use in a test tube and keep that volume constant through the experiments. I also have to keep the time constant through all my experiments, because if the time is increased, there will be more carbon dioxide gas collected in a given concentration of acid. To keep the time the same I will use a stopwatch, so that I can easily check the volume of the acid at the same time. I will repeat all experiments three times, so that the experiment will be more reliable.
I have now carried out an experiment to investigate the accuracy of the top pan balance that I will be using.
I placed ten nails in a Petri dish of weight 6.44g, and placed them on the top pan balance.
I weighed the Petri dish containing the ten nails 7 times and recorded the different readings:
7.50g, 7.50g, 7.51g, 7.50g, 7.51g, 7.50g, 7.49g- the range is 7.51g-7.49g=0.02g
The range is 0.02g, so I can conclude that my top pan balance is accurate, give or take 0.02g.
Observation
My results are tabulated below:
I also observed that the calcium carbonate did not all disappear after five minutes.
This is a graph of results:
Analysis
In conclusion, my graph shows that increasing the concentration of acid also increases the amount of gas collected, which means an increased rate of reaction.
My graph shows me that the rate of reaction was fast initially, it then started to slow down, that is the reason I have a slope. This shows that not only did the volume of gas collected increase in proportion to acid concentration, the differences between each increases decreased as the acid became more concentrated. The theory behind this is that as the acid concentrations increases, there are more acid particles to collide with the calcium carbonate, there is then greater chance of successful collisions, therefore more carbon dioxide is produced, and then there is a faster rate of reaction. I will divide my graph into 2 sections-Section1, Section2.
Section1- The rate of reaction is fast probably because there are more acid particles coming in contact with CaCO3.
Section2- This part is less steep probably because most of the CaCO3 has been consumed, so the rate of reaction is slowing down.
My prediction was that the acid concentration will be directly proportional to the gas collected and it fits with my conclusion that as the acid concentration increases, the more gas collected, therefore the faster the rate of reaction. For my predicted graph, I drew a straight line graph denoting constant increase, however, my graph of results proved me wrong as it showed me that there was a varying increase, which became less and less as concentration was higher.
Evaluation
I think my procedure was quite detailed and could be easily followed. As the top pan balance fluctuated a lot, I did an experiment to find out its accuracy. The experiment is detailed in the planning of this investigation. From that experiment, I found out that the top pan balance was accurate to 0.02g.This means that my measurements are accurate give or take 0.02g. I also took the volume of the acid at the lower meniscus; this makes my results more accurate. I think that my experiment was quite accurate and if it were to be repeated, I would get similar results. Furthermore, I took an average of three results; therefore, there was less chance of an anomalous result.
I believe that my investigation was valid because I ensured that the same apparatus was used through out all the experiments. I kept the temperature constant by doing all the experiments under a ceiling fan; I kept the weight of CaCO3 constant by weighing 0.5g of CaCO3 for each experiment to an accuracy of 0.02g; I kept the volume of acid constant by measuring its volume before each experiment to 15ml; I kept the time taken by each experiment constant by using a stopwatch; I made sure I changed to a fresh connical flask and test tube at the beginning of each experiment, I also made sure I changed the acid concentration of the hydrochloric acid to the appropriate one for each experiment. By keeping these factors constant throughout my investigation, it shows that my investigation is valid. I think the information I have collected is enough to support my final conclusion that the concentration of acid is directly proportional to the carbon dioxide collected, therefore, directly proportional to the rate of reaction. Also that the increase in carbon dioxide collected is not constant, so the rate of increase is not constant.
If I were to repeat this experiment again, I would use a more accurate top pan balance for my experiment so that my results will be more accurate.
To obtain more evidence to support my conclusion that the acid concentration is directly proportional to the rate of reaction, I would take the results five times and get the average result. This means that my investigation and my conclusion will be more reliable.
