I will repeat this process again for 0.25, 0.5,0.75 and 1 molar acid. I keep the volume of acid and the mass of limestone the same for each experiment as to keep it a fair test.
Then I repeated the entire process again 2 times so that I could get average results. During my experiment I will control all the variables to the best of my ability. I will record all my results in a table.
5) Making a fair and safe test
I will wear safety glasses to protect my eyes from any accidents that may occur. I will have to check the apparatus for any broken pieces, that way, I can avoid injury to myself or avoid a mistake in my experiment through a leak. The most important thing is safety. After checking that everything is safe, I will plan the actual experiment.
I will try to make it as fair as possible by trying to take the most accurate measurements at the most precise times. I will also make sure that the mass of Calcium Carbonate is precise and that in all the experiments done it is the same, or at least very close. I will also make sure that there is the same amount of Hydrochloric Acid in each experiment. If I do this I think my Hypothesis will be accurate.
Apparatus set up
The first thing I'll do when I start my experiment is to put my safety glasses on. Then I'll take all my equipment and make sure that nothing has leaks and that everything is clean, that the stopwatch works and that the gas syringe isn't stiff.
After I have checked that everything is in working order, I will begin setting up my apparatus as will be drawn below with the plan of my experiment. Setting up the stand will be the first thing I do. Then I will attach the clamps to it. After that, I will put the gas syringe into the clamps making sure that the level of it is even. Then I will attach the gas syringe to the beaker through the rubber tube with the cork on the end. I will then proceed by putting my beaker in a beaker holder and setting up my stopwatch so that I can have easy access to it. Then I prepare my pen and paper to record results. I then will take 15ml of Hydrochloric acid (Molarity depending on which one of the experiments I'm doing) and I will insert that into the beaker.
Following this step, I will weigh 1.5 grams of Calcium Carbonate. I will set this by my beaker. Then I will be ready. Starting my experiment will be a little complicated as I have to do three things at once so for maximum accuracy, will have someone else start the stop watch. I will insert the Calcium Carbonate into the beaker and will proceed to put the cork on as fast as possible. The person helping me then will start the stopwatch. I will record results every 30 seconds, which is about as close together as I can make it. That will be how I conduct my experiment. I think my plan is a good one because I try to make everything as accurate as possible, which is what I need.
The reaction should be perfect in all my experiment if I really conduct it as I have. I say this because my Calcium Carbonate reading is very accurate and the amount of Hydrochloric Acid (at different molars of course) will be very constant. This should ensure a predictable reaction and if that doesn't occur then something wrong must have occurred.
Planning and check ups:
I have to make the decision whether I'm going to keep the beaker still or whether I'm going to shake it. This is an important choice, as if I shake the beaker then I'll have to shake all of my experiments. However, I'm choosing to keep the beaker still.
Another factor that is very important is whether or not the gas syringe is leaking. If it is leaking, then my results cannot be accurate. Also, if it is stiff then it might jump form one place to another without sliding. If the amount of Calcium Carbonate differs too much in between experiments, then there is no way that they can be accurate. The amount of Hydrochloric Acid (20ml in my case) has to be constant also.
There are quite a few reasons why these factors are important. If the mass of the Calcium Carbonate varies then the Hydrochloric Acid will have more, or less, surface area to react on which would change my results greatly. Same for if I have more Hydrochloric Acid in my beaker, then the Calcium Carbonate will have more to react on and that would be unfair as well.
3) Prediction:
I predict that as the Molarity of the Hydrochloric Acid increases, so will the speed of the reaction in the gas syringe.
I predict that the higher the concentration of acid then the faster the rate of reaction.
Calcium Carbonate + Hydrochloric Acid => Carbon Dioxide + Calcium Chloride
CaCO3 + 2HCl => CO2 + H2O + CaCl2
I predict this because when a chemical reaction takes place, the atoms are broken loose from their arrangements and re-arranged into different groupings, forming new substances. The reaction above can only happen if the particles of acid came into contact with particles of limestone. In gases and liquids or in solutions, the particles are moving around freely and can bump into each other more easily.
In this reaction of acid and limestone, if the acid is very concentrated this means that there will be plenty of acid particles close together in the solution. Acid particles collide with the calcium carbonate very frequently and if they do this, the surface of the limestone will dissolve quickly. If the acid is very dilute then the particles will be more spread out. They will bump into the limestone a lot less often and so the reaction will take longer. A general rule could be:
If the solution is more concentrated, the reaction will be faster
In this reaction, the limestone is a solid. Therefore the particles in a solid cannot move around freely and only the particles on the surface of the limestone can react with the acid.
Also there are different conditions in which the rate of the reaction changes and they will be:
- Temperature as it speeds the movement of the Molecules up so there’ll be more successful collides which lead to a higher rate of reaction
- Surface area: the less surface area the higher rate of reaction because there will be more successful collides between the acid particles and the limestone particles.
- Catalyst: speeds the reactions up and make the rate of collisions faster than their normal rate. And obviously concentration of acid which I opted to investigate.
8) Conclusion
Evaluating Evidence
I think the experiment worked well to a certain extent. It could have gone better. I got on confused when I did the experiment on 1.5M. I got confused because I lost track of the time. I still monitored the time every 30 seconds but as you see on my graph. There are some anomaly readings.
They are reasonably accurate as I found out from making a Molarity chart. Apart from my 1.5M results, all the others have almost smoothly curved graph. They were, at least from my point of view, accurate enough for this experiment. The experiments I made went as I predicted.
“ The higher the Molarity of the Hydrochloric Acid, the faster the reaction.” I deem them good enough for this experiment.
The second graph that I have drawn confirms my first one but as you see I found some anomaly readings in the second attempt as well and that must because of that I lost the track of time.
Comparing the graphs to one another you can see that the first graph looks lightly different
From the second one and that must be because of different sizes of limestone chips that I used.
In doing this experiments I have found that the higher the Molarity of Hydrochloric Acid when it reacts with Calcium Carbonate, the faster the reaction there will be. From the graphs I made you clearly see the pattern. It is not exact but you can see how 1M is more than 0.5M and 1.5M is bigger than 1M. The only problem with the pattern as you can see is that the 1.5M does not look like a nice and smooth curved. It should be a great deal higher than that, the reason for this was explained earlier in my write up.
The line graph shows you how the different Molarities went up at different levels. What I have really discovered is that when keeping everything the same, and changing the Molarity of the Hcl, the reaction goes faster.
The reason for this is that in the higher concentrated acid (e.g.: Hcl) there are more free Molecules to collide with the Calcium Carbonate molecules on the surface of the limestone chips
In the end, each experiment reached the same levels of gas volume it just took much longer with the 0.25M. It took so long that I was incapable of recording it on a graph. The more concentrated the solution is, the more Molecules there are and when they bounce around during a reaction, since there are more around them, they bounce back off of them. That is why the 1.5M and 1M reaction went a lot faster than the 0.5M or 0.25M.
My results turned out as expected.
My prediction was accurate as I said, the higher the concentration, the faster the reaction. I think that my prediction, graph and my results match perfectly with each other. In conclusion, I think that the experiment worked well in some places, and worst in others. Speaking for the overall, I think it went averagely.
9) Evaluation
On a whole I think that my procedure was quite reliable and suitable but there were a few certain aspects of my experimental work that I think I could have improved.
I have found some anomaly readings in the experiment, which made my graph don’t look like a smoothly curved line. These anomalies are because I wasn’t accurate on reading the gas syringe and also as I said in my conclusion I got muddled up in timing and the sizes or shapes of the limestone chips weren’t all the same.
In my experiment I have kept to my variables as best to my ability however there were some variables, which I could not sustain. Surface area of the limestone chip(s) was the biggest factor, which I could not uphold this was because each limestone chip consists of a different size and shape and I went on the variable of weight of the limestone chip(s). Therefore each of my 2.00 grams per experiment I accomplished might have had a bigger or smaller surface area each time. Another variable, which I had no control over, was the variable of temperature. I anticipated that the investigation would take place at room temperature, which is 24 degrees. However, I did not have the equipment or the facilities to control the temperature so if the temperature changed during the investigation, which I think it, did because we experimented over several days, and then the experiment might not be entirely fair. Another factor, which I could not be in command of, was pressure. The pressure created by the weather; I couldn’t take control of it because, once again I did not have the facilities. If the weather changed during the experiment then the pressure would have changed also. Once again this is a factor, which I could not of had any effect upon and this could have caused the experiment not to be entirely fair. I believe that I could have made the test better by using more accurate equipment, for example a more accurate Gas syringe to record results better, or an even harder task would be to try and work out the total surface area for each of the tests.
I think that one improvement that I could have made was to actually work out the exact time of each result I was going to take. Then I wouldn't have muddled up my timings when I conducted my experiment on the 1.5Ms of Hydrochloric Acid, that is one major improvement I could have made; I could also have made several other minor improvements when I look back on the rest of the experiment. Like the fact that I had a jumpy syringe and that my results were slow in some places due to the jumping around of the syringe.
I could have made sure that the syringe actually worked.
Overall I think that the way that I carried out the experiment was probably the best way to do it because it was short and simple without taking great detours around the actual point.
If I were to do the experiment again, like I said before, I would have checked the equipment first but otherwise nothing really would have happened. My results seemed to be reliable except for my 1.5M ones. I made a rate chart and all the others looked reliable. The 1.5M results really didn't fit into the main pattern but still it was all right.
I may, therefore, as further investigate into the effects of the other factors that effect rate of a reaction in HCL and CaCO3 again compare my results with these and I would investigate the effect of the surface area at which the reaction occurred, the temperature of the reaction I would also use because as I mentioned it can affect the rate of reaction immensely.
I think that I had enough correct results to draw a conclusion. It would have been better if my 1.5M experiment had worked but the 1.5M going wrong actually helped my conclusion in a way. I am confident that I was to draw an accurate conclusion.
I could have conducted a few more experiments to get my accuracy level to a higher level.
