Calcium carbonate reacts with strong acids such as Hydrochloric acid to give off carbon dioxide and water.

Preliminary results

To make the test fair, I used the same mass of marble chips each time and the same volume of hydrochloric acid too. I used the same concentration of acid every time so the concentration is the same. To keep the surface area of the marble chips the same, I made sure all the marble chips I used were small and therefore had similar surface area.
The preliminary showed that the experiment worked. The timeframe is not too long or short and it can be easily measured. The range is okay, but I must be careful to not go over 60ºC as I spotted some hydrochloric acid vapours, anything over 60ºC would be dangerous.


Experiment method


1. Set up the apparatus as shown in figure two.
2. Put 25cm³ of hydrochloric acid (two molar) into a 100cm³ graduated cylinder.
3. After doing this pour the hydrochloric acid into the Buchner flask and take the temperature using the thermometer, the temperature should be approximately under room temp of 20ºC for your first result.
4. Weigh two grams of calcium carbonate chips on the 0.1 weighing scale. Use a watch glass so it easier to put the chips into the Buchner flask afterwards and when weighing place the watch glass on the scale and then reset the scale so that the weight of the watch glass isn’t taken.
5. Start to add the calcium carbonate chips into the Buchner flask and at the same time start the stop clock and put the bung into the Buchner flask to prevent carbon dioxide escaping.
6. Stop the clock when you have collected 100cm³ of carbon dioxide gas in the syringe.
7. Record your results in a suitable.
8. Repeat steps one to seven for 30ºC, 40ºC, 50ºC and 60ºC of hydrochloric acid but this time use a Bunsen burner to heat up the acid. Heat the hydrochloric acid separately in a beaker over the Bunsen with a blue flame and use a thermometer to get to the desired temperature.
Experiment results

This is the first set of results that I obtained from the experiment.

I repeated the experiment again for the second time to gain more accurate results and to eliminate any errors.

After repeating the experiment readings twice, I took an average by adding the time to collect 100cm³ of gas from each temperature in the two experiments and then dividing the sum by two, to make the results again more accurate and to eliminate any more errors.

After finding out the average results for the rate of carbon dioxide gas production graph, I have made another graph to show the rate of the reaction between the calcium carbonate chips and the hydrochloric acid. I have worked the points out by taking the average time for each temperature and dividing it by one i.e. 1/T

Conclusion & analysis

As I predicted in my hypothesis, that as the temperature of the hydrochloric acid will increase, the rate of reaction will increase and the atoms in the hydrochloric acid will be more energetically favourable. The atoms will travel faster with energy, causing more collisions and the rate of carbon dioxide gas production will also increase.
The higher the temperature, the faster the reaction rate there will be. This is due to the kinetic theory. The more heat that is given to matter, the faster the particles will move. This happens in the acid, so the faster the particles move, the faster the reaction rate due to more collisions between the marble chips and the acid.
If you observe the average results graph, (figure three) you can see that as the temperature of the hydrochloric acid increases the time taken to collect 100cm³ of carbon dioxide gas decreases and this shows that temperature does affect the rate of the reaction and the rate of carbon dioxide gas production. If you observe the time taken to collect 100cm³ of gas from 20ºC of hydrochloric acid it took 59.83 seconds, whereas 60ºC of hydrochloric acid took 23.38 seconds.
However the 60ºC time of 23.38 seconds was a slight anomalous result perhaps due to the acid temperature not being accurate enough because the acid was heated by the Bunsen burner meaning that the temperatures were not constant and you can observe this on the average results graph. The one over time graph (figure four) shows the rate of the reaction between the calcium carbonate chips and the hydrochloric acid and if you observe the graph you can see that the 60ºC time again is an anomalous result.
Therefore my conclusion is that the white cliffs on the Antrim coastline are eroded less in the winter due to the acids being low in temperature in the rain even though there is more rain, whereas in the summer the acids in the rain are warmer causing the white cliffs to erode at a faster rate than in winter.


Evaluation

The experiment worked well even though I had one anomalous result.
To improve the experiment and to obtain better results, the surface area of the marble chips could be decreased and instead of using small calcium carbonate chips, powdered calcium carbonate chips could be used to make the surface area even more accurate. Therefore the hydrochloric acid that would be used with the powdered calcium carbonate chips would have to be weaker because the reaction would occur too fast.
Also instead of using a Bunsen burner, a water bath could be used instead to keep the temperature constant and to obtain more accurate results.