Reaction Rate Investigation

The reaction rate can be increased if the concentration of the reactant is raised. As there are more particles to react with in a higher concentration of acid, the chance of an effective collision goes up. I have performed similar experiments and have acquired this equation:

Calcium + Hydrochloric Calcium + Carbon + Water

Carbonate Acid Chloride Dioxide

The reaction rate is also known as the collision theory. This is when successfully 2 particles collide with each other and give off a successful product. This is as shown below:

For my experiment I will use 5 different concentrations of hydrochloric acid. These are:

0.5M

M

.5M

2M

2.5M

When the apparatus has been set up as shown above, 25 cm3 of 0.5 M acid solution will be measured using a measuring cylinder. This will be poured into a test tube. I will then get 5 marble chips, all weighing 1g each. I will then set up the gas syringe, on a stand. This will be connected to a delivery tube, into a bung, into a test tube. The test tube will be placed in a cold water bath to ensure the temperature will be kept the same, as the reaction is slightly exothermic. The test tube will have the sufficient concentration of Hydrochloric acid in it. The chip will be placed in and immediately the bung will be placed over it. I will start a timer and after 4 minutes the amount of gas given off will be recorded. This will be repeated until all 5 chips have been used in the different concentrations. I will do the experiment twice to obtain accurate, reliable results. When all the results have been obtained, I will draw a graph of the results.

During the planning stages, I did a few preliminary experiments. At first, I was going record the amount of gas given off every 30 seconds until the reaction rate had stopped. This took an extremely long time and with the highest concentration it eventually went off the scale and too long to stop completely.

I also tried using powdered marble chip to see if the reaction would be quicker. But on the highest concentration, 1g of powdered Calcium Carbonate over flowed and fizzed too violently. I eliminated this method immediately.

Obtaining Evidence

Whilst carrying out my experiments, I only made two changes. This was that I did two extra concentrations. These were 1.25M and 2.25M. Doing these extra concentrations made my results more accurate. I also replaced the water in the cold water bath each time. This made the experiment a much fairer test.

These were my results:

Concentration (M)

Amount of gas given off after four minutes (cm3)

st experiment

Amount of gas given off after four minutes (cm3)

2nd experiment

Average amount of gas given off (cm3)

0.5

2.5

3

2.75

.0

6

5

5.5

.25

24

28

26

.5

36

34

35

2.0

42

41

41.5

2.25

62

61

61.5

2.5

78

81

79.5

Analysis

My results were very successful, and no anomalous results were obtained. I have displayed my results in a graph:

As the construction lines show, in most cases, as the concentration doubles, the amount of gas given off doubles. This supports my prediction and that when the reaction rate is increased the concentration of the reactant is raised. As there are more particles to react with in a higher concentration of acid, the chance of an effective collision goes up, and the rate increases. When the concentrations increased, it did fizz more violently in the test tube, resulting in giving off more Carbon Dioxide.

Evaluation

The results I have taken and analysed are very reliable results. A firm conclusion can be made from these results, that as the concentration doubles, the amount of Carbon Dioxide given off is also doubled. The results supported my prediction well and no anomalous results were obtained. My results were as accurate as they could be; I used the same equipment, in the same environment for all the tests. Overall it was a fair test.

My method was very successful, although a few changed could be made improve the test. The marble chips could all be cut into squares, as then they will have exactly the same amount of surface area and mass. The experiment could be carried out more times than twice, to achieve a more specific average. Also, more concentrations could be used, either with a smaller disparity in between, and the concentration of acid could go to a higher concentration. We were obviously limited in the laboratory as we could only use up to 2.5M.

James Bonner 11G