An experiment to show Calcium Carbonate reacting with Hydrochloric Acid.

From the information my graph gave me I noticed that as the concentration of acid goes up, so does the gradient, the rate of reaction then goes up as a result. This trend continues through all 6 concentrations. The rate of reaction would also go up if the surface area of the chips was higher. To make a better study I could also have done the same experiment with several different acids so I got a wider range of results. I would then be able to see if the trend was the same for all acids.

On each of the 6 separate concentration graphs I drew on tangents so I could find out the initial rate. The results I got for this were:

Initial Rate Table

Concentration of acid Mol/dm³

Initial Rate cm³/sec

0.2

0.18

0.5

0.37

0.75

.2

.02

.5

.08

2

.50

To make the experiment more accurate I could have used a divided flask (diagram below). This would make it much easier to record as the bung would already be on and the acid and limestone chips could be mixed quickly and safely.

I could also have recorded data every 10seconds, so I had more results and would therefore be able to see a pattern easier. Another thing I could have done is had a larger range of concentrations, I think 8 would have been a better number to have as it would be better to see a trend. I also would have checked the surface areas of the chips to make sure there is not a substantial difference between them for each experiment.

Another method I could have used to make the experiment more efficient is by using a syringe. This would make sure the stopwatch was started more accurately, as the bung would not need to be replaced which saves time and stops any gases escaping. (See diagram below)

Conclusion

I conclude that it is true for this experiment that as the rate of reaction doubles the concentration also doubles.

Evaluation

I think that overall the method was good. The results came out well as there were no obvious anomalous results. I think the gas syringe was a good way of measuring the Carbon dioxide as no gas could escape and it is easy to read the results off.

Although there were no anomalies, all the points did not lie exactly on the line. Some of this may be due to a change in temperature, this could be prevented by using a water bath. This is when you put the flask which will have the hydrochloric acid and limestone chips in, in a beaker with water in. the water will be at a set temperature, say 20ºC. This will be kept the same for each experiment. (See diagram overleaf )

Most points were close to the line. On the initial rate graph ( graph 8) there was a positive correlation. This means that the Rate of reaction is directly proportional to the concentration of the acid. I think one of the reasons the results had no anomalies is that all the experiments were conducted on the same day, which means they should all have been done at the same temperature.