The strategy I choose to take is that of placing the limestone into the acid, activating the stopwatch, and putting the bung in the top of the flask as quickly as possible. There will be 50 millilitres of water in the glass tube. I will allow the carbon dioxide to travel along the rubber tube, into the glass tube, where it will begin to displace the water. Every time 10mls of water is displaced into the tub below, I will take a time reading, stopping the stopwatch after the full 50mls has been displaced.
Obtaining the results.
The experiments are being carried out. It is being done under high safety conditions. I stay clear unless I am checking the displacement or time, and safety goggles are worn at all times. The equipment is all cleaned after each part of the test, so as not to mess it all up by mixing substances left over from one test with those applied for another test.
The results have been tabulated below.
These are the mean averages, taken by adding the two results together and dividing the answer by two. These were checked repeatedly, to make sure that they were the exact averages, rounded to the nearest whole second. This should therefore be accurate enough to draw an analysis and a conclusion from. The only possible anomalies here are that some gas was lost before the bung went on, or that the temperatures for each test were different enough to affect the results. Otherwise this would be perfectly reliable evidence to analyse.
Analysing the results.
The evidence collected shows simply that the stronger acid reacted quicker with the limestone, on average at least. This goes hand in hand with my prediction, so far. The results have been graphed in two ways, and these can be seen below.
Using the bar graph form of results, I can see that the weaker acid took a lot longer in the reaction with the limestone than the stronger acid did. This is the simple way of analysing the results.
Using the line graph form of results, I can draw a more detailed analysis, and this is the more complex method of analysing the results. All the lines are more or less straight, indicating that the reactions went on at a steady speed. The lines for the stronger acids are not as steep as those for the weaker acids, and this shows that the concentrated acids were reacting at a faster pace than the weaker acids.
In conclusion to this experiment, I say that the results were all matching with my hypothesis. The stronger acids were faster than the weaker acids. However, the temperatures were not recorded, so I have no information about how this may have affected my results. Overall, I conclude that hydrochloric acid reacts with limestone at varied speeds, depending mainly upon the concentration of the acid. This
could, however, be affected by temperature, but this was not recorded.
Evaluation.
The procedure I chose to use was, at the time, the easiest one to understand. It seemed easy to set up, and the evidence was recorded in varied forms; a table and two graphs. The evidence was, in the most part, reliable, but the temperature caused an anomaly in the results, however minimal it may seem. The reactions may have been slightly faster or slightly slower because of this. Also, a small percentage of the gas produced was lost before I could get the bung on. This extra gas could have displaced a bit more water at the start, causing the full 50 millitres of displacement to have ended anywhere up to 1 second earlier.
The procedure carried out was mostly suitable, but I could have done a few things differently. Firstly, I could have recorded a different set of results. For example, I could have recorded how much water was displaced in every minute as opposed to how long it took to displace every 10mls of water. Secondly, I could have changed some of the minor details, such as the size of the conical flask, or the length of the rubber tube.
From a critical point of view, I can see that my evidence was not as reliable as it could have been. However, it was reliable enough to draw a conclusion from. Overall, this experiment was reliable, but with the two potential anomalies, it may not have been completely trustworthy. It was, however, sufficient to support my conclusion.
Lit List.
- The collision theory was learned of from the chemistry text books in the lab.
- The word “anomalies” came from a dictionary.
- The principles of heat as a catalyst were learned through the teacher.
- The ideas of mixing various acid strengths to create different molarities were based on a set of formulae given to us by the teacher.
- The strategy for obtaining the results was chosen between myself and my colleague.
