Equipment
Hydrochloric Acid (HCl) - different concentrations of 0.5M, 1.0M, 1.5M, and 2.0M.
Calcium Carbonate (CaCO3)
Delivery tube
Bung
Conical flask
Plastic container
Boiling tube
Water (H2O)
Stop clock
Balance
Safety Glasses
Measuring Cylinder
Method -
The experiment I am doing will involve changing the concentration of the hydrochloric acid (HCl) to find out the speed of carbon dioxide during the reactions. My variable that I’m going to use is concentration gradient, therefore I will keep the temperature, surface area, volume of acid and mass of calcium carbonate (CaCO3) the same, as these factors affect the rate of reaction as explained earlier. I the temperature I will be using is room temperature as it is to much hassle to be taking the temperature at the same time as recording results, also this could cause me to take a wrong reading. I would measure the temperature and make sure it is at a constant but there was no availability of specialist equipment. I will use four different concentrations, 0.5, 1.0, 1.5, and 2.0, these are all measured in molars/M. Therefore I will be doing four different experiments. So I will need four different pieces of calcium carbonate (CaCO3) of the same size and weight of 0.5 grams. I will use 25ml of hydrochloric acid (HCl), so the ratio of the calcium carbonate (CaCO3) to hydrochloric acid (HCl) will be 1:5, meaning for every 0.1 gram of calcium carbonate (CaCO3) there will be 5ml of hydrochloric acid (HCl) for it to react with.
In my experiment I will firstly get all my equipment and set it up properly. I will then put 25ml of hydrochloric acid into a conical flask, from the conical flask there will be a delivery tube connected by a bung. The delivery tube goes into a plastic container filled with water, and then into the boiling tube submerged horizontally upside down so that it is totally filled with water and there is no air in it. After this I will remove the bung from the conical flask and drop in the 0.5 gram chip of calcium carbonate (CaCO3), and as quickly as possible I will seal the bung into the conical flask so that no gas will be lost. As soon as the calcium carbonate chip is dropped in I will start the stop clock, and the level of carbon dioxide will be recorded at 30 second intervals.
Preliminary experiment -
In the preliminary experiment I will be conducting, I hope to find out the ideal size of Calcium Carbonate (CaCO3) to use, also the ideal time intervals to use and volume of acid.
I have decided to use exactly the same set up and method as I would in my main experiment. In my preliminary experiment I will use pieces of Calcium Carbonate (CaCO3) weighing 0.6 grams. I will record the changes at every minute for only ten minutes, whereas in the actual experiment I would record the changes until the reaction stopped and the calcium carbonate (CaCO3) has fully dissolved. The concentrations I will use are of 0.5 molar, and 2.0 molar to act as the extremes and see if the size of chip, timing and amount of hydrochloric acid (HCl) is what I would use in my actual experiment. If I do all this then I can test how long it takes the calcium carbonate to fully dissolve, so that I can make any important changes, if needed.
Results of preliminary experiment - 75ml of acid
Intervals at every 60 seconds
Calcium Carbonate chip weighing 0.6 grams
Amount of carbon dioxide (CO2) measured in cm3
- = fully dissolved
Preliminary Conclusion -
My preliminary results show me that I need to make some changes. Firstly for the actual experiment I shall use calcium carbonate (CaCO3) chips of 0.5 grams as the 0.6 gram chips used in the preliminary were to big. Secondly I will change the amount of acid, in the preliminary experiment I used 75ml of acid and this was definitely to much as the calcium carbonate (CaCO3) dissolved much to quickly and it wouldn’t be practical. Also I will change the intervals at which I record the changes, in the preliminary experiment I recorded changes every 60 seconds, whereas now I have decided to record changes every 30 seconds to make it easier to see patterns and to give clearer results.
If I do this I think it will ensure I have good quality results, and be able to recognise patterns.
Hypothesis -
My hypothesis is that the higher the concentration of acid, the faster the rate of reaction, which will mean carbon dioxide (CO2), will be given off at a faster rate. I think this because as the concentration increases the amount of particles of reactant will increase allowing more collisions and at a faster rate.
Main Experiment -
On the following 2 pages you will see a table showing the results of my main experiment, and you will also see a graph representing the data collected.
Analysis -
My results show me a number of different things. On my graph you can see a pattern which is that the is a slight curve which represents that there was a steady increase in the amount of gas given off. If the curve was steeper this would mean that there was a much more rapid increase in gas given off. Some were steeper than others so this means that my experiments were contrasting. My results show that the experiment that gave off the most carbon dioxide (CO2) was the experiment with a concentration of 1.0M, which gave off 66.0 cm3 of gas. The experiment that gave of the least amount of gas was the 0.5M experiment which only gave off 36.75 cm3 of gas. The 1.5M experiment was the fastest experiment which only lasted 630 seconds (10.5 mins), the longest experiments lasted 1140 seconds (19 mins) which were the 1.0M and 0.5M experiments.
Conclusion -
My results show me that my hypothesis was correct and that the higher the concentration the faster the reactions and the faster carbon dioxide (CO2) is given off. I recorded no anomalous results and recorded precise data. I think that my experiment was performed successfully. I realised that the lines on my graph should have eventually met. They should have done this because I used the same amounts of calcium carbonate (CaCO3) and hydrochloric acid (HCl) in every experiment and therefore the end amount of gas should be the same. I realise that this did not happen and I think this would be down to the experiment being inaccurate. Using the graph I can compare the different experiments to each other. I also realised by doubling the concentration, the rate at which calcium carbonate (CaCO3) should double. e.g. the 2.0M experiment should have gone twice as fast as the 1.0M experiment, and the 1.0M experiment should have gone twice as fast as the 0.5M experiment. My results follow a trend and proved accurate as I did two experiments for each concentration and I think the continuation of certain experiments would of proved this even more so. If there had been any anomalous results it would of been because of an error I had made in the experiment e.g. not weighing out the calcium carbonate (CaCO3), or measuring the amount of hydrochloric acid (HCl) inaccurately. In my experiment I had no anomalous results which proved all of my measurements were correct. To make my results more reliable I could have improved the equipment I used e.g. using a gas cylinder instead of a measuring cylinder, which would of enabled me to read results accurately without the risk of escaping gas during the process. I could of also done many more experiments with different concentrations, and also if I had more time I would of been able to take more time over my experiment which would of made it more reliable. Also I could have made my results more reliable by controlling the temperature. The reason I didn’t do this in my experiment was because I did not have the correct equipment or the time needed to do so. In my experiment there may of been some inaccurate calculations, which should have been located and recalculated, if this applied to my experiment.
The reason that the experiments with higher concentrations gave of gas at a higher rate was because of particle theory. This affected it because the stronger the concentration the more particles there are to collide with and overcome the activation energy required, therefore a faster reaction occurs.
In future experiments I would conduct my experiment differently. For example I would do a longer more detailed preliminary experiment to make sure no confusion or impractical methods were used during my main experiment. I also would measure the change in rate when the reaction is occurring whilst there is another variable e.g. surface area. A simple procedure for this experiment would be:
- Put a piece of calcium carbonate (CaCO3) weighing 0.5 grams in 25ml hydrochloric acid (HCl) with a concentration gradient of 1.0M.
- Set the stop clock.
- Record results every 30 seconds until reaction has stopped (when the calcium carbonate (CaCO3) has totally dissolved).
- Repeat experiment but crush calcium carbonate (CaCO3) into powder.
- Repeat experiment but crush calcium carbonate (CaCO3) into smaller pieces.
- Repeat experiment 2 times for each different surface area and find the average.
- Display results on a table and graph.
To also find out if my hypothesis was true in the future I could change the reactants, to see if increasing the concentration of acid increased the rate of gas given off other elements, for example, Magnesium (Mg) and Hydrochloric acid (HCl) and collecting Hydrogen (H).
Overall I enjoyed conducting my experiment and in the future I would enjoy doing future research into rates of gas given off.