I have analysed my data and presented them in graphical form. The first graph shows the averages between the three experiments. The second compares the times taken to reach 100 cm cubed of carbon dioxide for the application of all concentrations based on average results. Graph 1 shows that the gradients were much steeper with the higher concentrations of acid. This means that the reaction had a faster rate as it produced more carbon dioxide at a faster speed. My observations on the higher concentrations are that they were a lot more violent than the weaker ones.
This was because of the more effective collision that the higher concentration caused, as there was I much higher chance of a reaction occurring due to the large presence of acid molecules in the solution. Graph 1 of my experiment shows the averages of my three tests. I have compared time, in seconds, against the average up till the point where the fastest reaction reached 110 cm cubed or it passed the 5-minute mark. The initial minute of the graph was the fastest section in all cases as there were more acid molecules available for reaction with the calcium carbonate.
See figure 4 for more information. The gradients of the graphs began lessen showing a slow down as they continued through the reaction because there were less acid molecules available to be reacted with. I believe that my results were valid as my results were consistent at each stage, most of the concentrations appeared to be the same and if they weren’t then the averages still managed to further validate my predictions. I believe that there is some type of ratio between the times taken to reach 100 cm cubed of carbon dioxide.
By looking at my second graph I can see that there is a constantly increasing difference between the concentrations of acid and the time taken to reach 100 cm cubed of carbon dioxide. The time is constantly increasing with each decrease in concentration. It is safe to conclude that the concentration of acid in the solution directly affects the amount of carbon dioxide produced. The carbon dioxide is a product of the reaction between the hydrochloric acid and the marble chips. The reaction is due to the violent and fast reactions, which are highly common in higher concentrations, as the re is more acid to be reacted with the calcium molecules.
EVALUATION I would have to comment that my results were fairly accurate, as the range of the results is fairly similar in most cases apart from a few which are made to look better when they are converted to averages. From looking at my results I can see that there were no poor outcomes, which was a good thing and it proves that the experiments were consistent. The method I used was effective when proving my point but I believe it was not accurate enough. The meniscus of the liquids placed into the measuring cylinders may have caused some inaccuracy when measuring and reading.
The fact that the 100 cm cubed measuring cylinder was upside-down may have caused some slight errors when reading and recording results. I also think it would have been a good idea to attempt to record the temperature of each reaction, as that may have helped to explain any anomalies that I had encountered. It would also have been useful to know what more about the cleanliness of the equipment as there may have been extra catalysts in the equipment used that may have affected my results in some way or another. I think the information is good enough to support my prediction as it proves most of the points I made.
The anomalous results I got in most of the cases had extremes at either end of the middle value. Therefore these values equaled out to form a better average than most other results. Before I did the experiments I predicted that the greater the concentration of hydrochloric acid was the quicker the carbon dioxide would be produced. This was completely correct because what I predicted would happen occurred. 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. The further work I can suggest for this type of experiment is to experiment with different temperatures, different pH of acid, and different types of acid or even mixing the acid to see which combination produces the most carbon dioxide. Table to explain the different acid concentrations: Number Volume of acid cm cubed Volume of water cm cubed.