What effect does concentration have on the rate of reaction?

Equipment List

Marble chips

Hydrochloric acid

Flask

Delivery tube

Container

Measuring cylinder

Stop clock

Safety

To keep the experiment safe I will push all stools under desks and make sure not to spill any acid. If any is spilt I will clean it up as soon as it is spilt.

Fair Test

To keep the test fair I will have to keep all the variables the same, I will collect the same amount of carbon dioxide each time. I will always use 50cm³ of acid. If I use more acid, there will be more acid particles in the solution, therefore increasing the chance of a successful collision. I will use the same weight of marble chips each time so there is always the same amount of marble for the acid to react with, and use the same number of chips each time, as surface area can affect the rate of reaction. If there are more pieces the chances of them being hit increase as they cover more area.

Trial Results

Strength of acid (M)

Weight of marble (g)

Time taken to collect 20cm³ CO2 (sec)

2M

0.2g

33.59

0.25M

0.2g

633.00

Analysis of Trial

From my trial experiment I have decided to use 2g of marble chip, collect 10cm³ of carbon dioxide and use 0.5M acid for the weakest acid strength.

Plan

To perform the experiment I will gather the equipment and set it up as shown in the diagram below. After setting up the equipment I will add 50cm³ of hydrochloric acid and as quickly as possible place the delivery tube in the flask, and start the timer. After collecting the desired amount of carbon dioxide I will stop timing and record the results. I will then repeat the experiment until all required readings are recorded. I will use the following strengths of acid. 0.5M, 1.0M, 1.5M, 2.0M, 2.5M, 3.0M.

Results

Acid Strength

Time Taken to collect 10cm³ of CO2

Average

0.5M

497.85

272.57

385.21

.0M

13.92

29.00

21.46

.5M

57.09

61.80

59.45

2.0M

53.75

40.68

47.21

2.5M

28.02

28.33

28.18

3.0M

27.19

25.08

26.14

Analysis

After completing my experiment I have analyzed the results and found them to be quite accurate, my average results fit the curve, apart from one anomalous result, the result for the 2.0M strength of acid. I think this result could be because of the chips sometimes having a coating on them, sometimes delaying the reaction slightly. If this is the case, if I ever repeat the experiment I will rinse the marble chips before I begin the experiment.

Evaluation

From my results I can see the experiment was quite reliable and I recorded some accurate results. However, if I ever repeat the experiment I will try and make it even more accurate. There are things I could do to make the experiment more accurate than it was. I could rinse the marble chips before putting them in the acid so the protective coating on them is rinsed off, making the reaction begin as soon as the marble enters the acid, instead of having a chance of the reaction being delayed. I could try and keep the temperature of the acid constant before it enters the flask as if the temperature increases, the acid particles will move around faster, causing more collisions, affecting the rate of reaction making the experiment less reliable.