Apparatus
20cm3 of hydrochloric acid
- 1 gram of marble chippings
- Side arm test tube
- Rubber bung
- Clamp Stand
- Measuring Syringe
- Measuring cylinder
Preliminary Experiment
I did a preliminary experiment so that I could find out the relevant information for me to use the appropriate concentration of the solution and the correct apparatus. During my experiment many things went wrong, for example the concentration of hydrochloric acid was too low and I had too many readings. On the other hand I used a too strong solution and I didn’t get many readings at all. To overcome this problem I used concentrations that weren’t too strong or too weak, I did this by trial and error.
Results
Method
First of all I am going to test the rate of reactivity of the calcium carbonate (marble chips) at room temperature (20°C, this is because that is the average heat of a room). I measured 1gram of marble chips and added them into a test tube and 20ml of hydrochloric acid into a measuring cylinder. I added the acid into the test tube with the marble chips and started the stopwatch. After 10 seconds and every 10 seconds I measured the amount of gas in the syringe until the acid had finished reacting. After each time I will throw away the marble chips because they cannot be used again as some reactant will have been used up. To get the best possible results I am going to test it 2 separate times to enable me to judge the amounts of gas produced fairly and decide if they are correct,
Diagram
Safety
As this experiment includes acid, which is corrosive, I will need to wear goggles. In addition I should wear an apron so that the acid can’t touch my skin or clothes. Also I should tuck my tie in and that the rubber bung on the conical flask is securely on.
Fairness
To keep it a fair test, the variables need to be kept the same to prevent getting the wrong results. The temperature of the acid needs to be accurate to get the correct rates of the reacting marble chips. The size of the marble Chips needs to be kept the same because of them either having a larger or smaller surface area for the acid to react with. If it has a larger surface area than the previous chips the results would be wrong because it has a larger area to react with, therefore the time it would have taken would be more than should be. If it were compared to the smaller chips the time would be less because of it having a smaller surface area for the reaction to act on. The Hydrochloric acid cannot be used again after the reaction otherwise the acid will be less strong to act on the marble chips. Everything should be kept the same except the concentration of the hydrochloric acid and the marble chip. The marble chip will be 5 grams every experiment.
Prediction
My prediction is that if the concentration of the acid increases there will be an increase in the rate of reaction for example the highest concentration will have the fastest reaction time. I used a preliminary test to help in the prediction. By using the results I can make the prediction that, the rate of reaction is affected by concentration. If the concentration of an acid increase then the rate of reaction will also increase. When the acid has a high concentration that means in that solution, compared to a dilute one there are more particles available to react with therefore the amount of times they will collide with the each other is more. So I predict the higher the concentration of hydrochloric acid the more collisions there will be and the more carbon dioxide will be produced.
Analysis and Conclusion
My results show that as the concentration of hydrochloric acid increased so did the rate of reaction. As you can see in my graph the rate of reaction at 2 molar was far greater than that of 0.25 molar.
I have found out that during my experiment the collision theory took place and my prediction was correct. I can conclude this by looking at my graph.
On my rates graph you can see that there is an almost straight diagonal line, of strong positive correlation, which indicates my results were correct.
I can conclude that rate of reaction is effected by the concentration of hydrochloric acid.
From looking at my results and graph I am able to conclude that the more concentrated the acid the quicker the reaction happened and the more gas was produced. As we look at the graph we can clearly see that in all five results at the beginning the reaction happened more quickly than at the end where we can see that it started to tail off.
Before I did the experiments I made some predictions they were that the more concentrated the acid was the quicker the reaction would happen and more hydrogen would be produced. This was completely correct because what I thought would happen did.
At this point we are able to answer our main hypothesis, which was 'how does changing the concentration of acid affect the rate of reaction between hydrochloric acid and calcium carbonate.' The answer to this would be that changing the concentration of the acid will either make it go slower or quicker and more or less gas would be produced depending on whether the concentrations were more or less.
Overall this was a very successful experiment and everything went very smoothly, and that was why my results were very reliable, and I am able to make a conclusion like this.
Evaluation
I think that the experiment went very well. This is because I got all the results that I expected and they look very conclusive. I feet I have accurate results and I have done the experiment to the best of my ability and so I am able to make a good conclusion.
From looking at my results I can see that there were no poor results, which was a good thing, and it proves that everything went very well.
The only possibility of error was if the temperature of the acid had changed from when I did the first reading to the end i.e. from when I did the first experiment the room temperature did not change and, hopefully the acid would have been the same temperature.
From looking at my results and graph I am able to conclude that the more concentrated the acid the quicker the reaction happened and the more gas was produced. As we look at the graph we can clearly see that in all results that as the molarity got higher the reaction speeded up. Before I did the experiments I predicted that the more concentrated the hydrochloric acid was the quicker the carbon dioxide would be produced. This was completely correct because what I thought would happen did.
My apparatus was very sensitive and accurate especially the gas syringe, which is accurate to 1cm3. My results were reasonably reproducible in that most results were within 2cm3 of each other. My experiment was relatively easy to set up apart from keeping the temperature of the acid the same.
At this point I am able to answer my main hypothesis which was how does changing the concentration of acid affect the rate of reaction between hydrochloric acid and calcium carbonate? The answer to this would be that by changing the concentration of the hydrochloric acid it will either make the rate of reaction slower or quicker and more or less gas would be produced depending on whether the concentrations were more or less.
If I could do the experiment again I would have liked to have used exact cubes of marble chippings with the same surface area and weight. This would have made my experiment much more accurate.
Appendix
I have used a few books and resources to help me with my project: - My note book, GCSE Chemistry - Gallagher and Ingram text book, the Internet GCSE chemistry revision www.scool.co.uk Encyclopedia Britannica http:www.gsceworld.co.uk http://pc65.frontier.osrhe.edu http://www.scidiv.bcc