Naturally, the more calcium carbonate used the more particles there are available to collide with the acid particles, and the faster the calcium carbonate reacts with the acid. The same goes with the amount of acid used the more particles you have, the more collisions can occur.
The temperature of the acid would greatly affect the rate of reaction as the higher the temperature of the acid is, the more energy the acid particles have. Therefore the particles will move around a lot faster and collide a lot more.
If you decrease the temperature the particles will have less charge and will move around slower, decreasing the number of effective collisions.
A catalyst is a substance which increases the rate of a reaction without changing it or being used up in the reaction. So by using a catalyst, in my experiment I would effectively speed up the rate of the reaction. The information I used to base my ideas on was obtained from a text book called ‘Chemistry Made Clear’.
Predictive Graphs Here are three predictive graphs showing what I expect to find from each of the three different surface areas.
On the next page is a fully labelled diagram of my apparatus, set up and working.
Here is a list of the chemicals (and amounts) and the apparatus I will be using to conduct my experiments:
I will display my findings in a table just like this one:
Large Surface Area
Method I will repeat each experiment three times. I will do three tests with large calcium carbonate chips, three with medium calcium carbonate chips, and three with powered calcium carbonate chips. The reason I will do each test three times is so I have a fair, reliable and accurate set of results.
To conduct the tests I will firstly set up my apparatus by filling a water bath full with water, inserting a rubber bung with a tube attached into the opening at the top of conical flask, placing the tube down into the water and up into an upside down, water filled, 250ml, measuring cylinder (for reference, see diagram, previous page). I will then accurately measure out 25ml (an amount which will stay the same throughout the experiment) of hydrogen chloride using a 50 ml measuring cylinder and carefully pour it into the conical flask. Next I will weigh out 40grams of large calcium carbonate chips (as this is the size I will begin my testing with, followed then by medium, and then lastly, powered). I will prepare my stop clock so I am ready to start the timer as soon as I pour my calcium carbonate chips into the acid. When I am fully prepared I will remove the rubber bung, which will be covering the conical flask whilst I am setting up for safety reasons, (to avoid spilling it and hurting someone) and pour in all of the calcium carbonate chips, and quickly replace the bung, to begin the experiment. Once the calcium carbonate has been added to the hydrogen chloride the reaction between the two will begin. I will then keep watch and every 1 minute I will write down how much carbon dioxide has replaced the water in the upside down measuring cylinder in the bowl, until the carbon dioxide has completely replaced all the water (the carbon dioxide has reached 250ml).
To make sure I get exact and reliable results I need to take some precautions to ensure I get a fair test each time I carry out the above experiment. These precautions consist of:
P.T.O.
There are also some safety precautions that need to be enforced when doing my experiment for the safety of myself and others around me. I must wear goggles at all times when around harmful chemicals of any kind, such as hydrochloric acid and I must tuck my school tie into my shirt as it could dangle and get in the way of what I am doing, possibly knocking over dangerous chemicals/equipment. I must also make certain that my hair is tied safely back, away from my face so it does not obstruct my work or obscure my view. And finally all stools need to be tucked under desks as I may trip or stumble over on of them, spilling harmful chemicals and endangering myself and others around me.
The independent variable I will be changing is the surface area of the calcium carbonate chips.
The range of values I will use range from 0ml to 250ml.
I will use at least 8 values for this variable. The reason for choosing 8 is explained later on under the ‘preliminary work’ section. The interval between the values obtained will be 1 minute.
The variables I am keeping the same are the amount, concentration, and temperature of the hydrochloric acid and the amount of calcium carbonate used.
My experiment will be a fair test because I will keep everything the same except for the independent variable (the surface area of the calcium carbonate chips). I will ensure my experiment is fair by checking that everything is the exact same way it should be before I being the experiment and if anything is wrong I will being the test again.
The results I obtain from my test will be reliable and precise because I will always keep my dependant variables the same. I will record adequate evidence and I will always ensure my tests are fair.
Observations In this experiment I will be measuring/observing and then recording the amount of carbon dioxide produced in the reaction between calcium carbonate and hydrochloric acid. I will repeat each of my 3 main experiments (large chips, small chips, powder) 3 times so as to get a adequate range of results and then be able to also have an average.
Preliminary Work Preliminary work is done to ensure that when the actual experiment is carried out nothing will go wrong. Preliminary work is a sort of ‘dress rehearsal’ for the real experiment, doing everything exactly the way it will be done for the real experiment to ensure that nothing will go wrong and to check that what you planned to do will actually work and will give you the most adequate and accurate results possible. For my preliminary work I carried out each of my main experiments (large chips, small chips, powder) just once to check that the method I had chosen would work, the time I had allowed would be enough to get the results I needed and apparatus I had chosen would respond in the way I wished it to. Below are some notes I made on my preliminary work.
P.T.O.
As can be seen from my notes, my preliminary worked proved to be useful for my experiment. From it I have made a few useful changes, such as the intervals when recording to make sure my investigation goes according to plan. Below is an example of one of the sets of results I obtained from doing my preliminary work.
Large Chips
This demonstrates that using the two minute interval was too fast and didn’t get detailed enough results.
Here is an example of the graph I will be drawing to display my results:
N.B. This is just an example graph and does not display my actual results.
Results Here are my table of results, complete with the actual results I obtained from carrying out my experiments.
Large Calcium Carbonate Chips
Small Calcium Carbonate Chips
Powdered Calcium Carbonate
The acid I have used throughout my preliminary work and actual testing has always been 2 molar.
Analysis From my testing I can see that my prediction was correct, and when I increased the surface area of the calcium carbonate chips, I also increased the number of effective collisions that occurred, which in turn sped up the reaction, causing faster production of Co2. Also, as predicted, when I decreased the surface are of the calcium carbonate chips, by using large chips, I decreased the number of effective collisions that occurred, slowing down the production of Co2.
The above statement matches that of my prediction, proving that my prediction was correct. As I have said, the reason my prediction is correct is that when I increased the surface area, I also increased the rate of production of Co2 when the calcium carbonate reacted with the hydrochloric acid. The reason this is true is because of the collision theory. When the surface area is increased the number of particles available to the acid to react with increases, which then increases the number of effective collisions that can occur between the two. (For more information see pages 1 & 2).
The relationship between my variable and my results are: As the surface area of the calcium carbonate chips increases, so does the production of co2.
There is one anomalous result in my table of results. This is test one of my powdered calcium carbonate chips. The volume of Co2 is at 225ml after one minute but after two minutes it has rapidly increased to a full 250. None of the other powdered chips did this. There are a few reasons that could have explained this odd result. The temperature of the acid may have been slightly higher as it may have been a hot day. Or maybe the conical flask was knocked slightly, which may have sped up the reaction.
Evaluation The suitability for obtaining accurate results for the environment I was in was adequate, considering the surrounding. As I was in a small classroom full of other students, I had limited space and equipment. However, I feel I coped well with this and used the apparatus I had to the best of my ability to get the most out of the experiment I did. I feel the procedure used (turning the measuring cylinder upside down in a water bath and connecting it to a conical flask) was not the most effective of ways to measure the rate production of Co2 but was adequate, in the circumstances, to obtain reliable results.
Errors that may have been made during the experiment were I may have not been able to ensure that the measuring cylinder was completely full every time, as I only had a limited amount of time to complete all of my experiments, so I could only have a few tries to get it exactly right. Also, some errors out of my control may have affected the result, such as the temperature of the room, and the amount of people moving around, affecting my experiment, in the room.
The reliability of my results was fairly accurate, as the majority of the time I was very accurate with my weighing and measuring, however, things such as the environment the experiments were done in could have been improved, which would have improved the accuracy of my findings.
If I were to do this investigation again there would be several things I would improve upon. I would look for a more accurate way of conducting this experiment, although I don’t exactly know how this would be done, I would like to find a more accurate way of collecting the Co2 produced, as I feel having an upside down measuring cylinder sticking out of a water bath is not really and accurate way of collecting evidence.
If I were to do extension work for this investigation I would look at the way the temperature of the acid affected the rate of Co2 produced as collision theory says that the higher temperature of the acid, the more charge the particles will have, speeding up the number of collisions that will occur, which will speed up the production of Co2. I could also look at the way the concentration of the acid would affect the rate of reaction, as I predict that the higher the concentration of the acid, the faster the reaction will occur.
