Surface Area and Rates of Reaction Between Mable Chips and Hydrochloric Acid

In chemical reactions, existing bonds in the reactant particles have to be broken down first before new bonds are formed to produce product particles2. Reactions only occur if colliding particles have more than a minimum amount of energy. This energy is known as activation energy (EA). It acts as a sort of 'energy barrier' unless particles have more energy than the activation energy, the reaction cant take place. A catalyst is can be used to lower this minimum energy.

As a result, of increase in surface area, I predict that there is greater area for contact between the chips and the acid for reactions to take place therefore increasing rate of reaction. The rate simply depends on how fast and often particles collide with each other.

The energy (gas) given off becomes more as surface area increases, therefore I predict the reaction using the powdered chips will produce the highest amount of gas in the slowest time. I am going to time each reaction for 3 minutes except for the powdered chips which I am going to time for only 1 minute because I predict the reaction is fast and takes place in a short period of time.

Based on my own knowledge, if I were to predict the shape of the graph for a certain size of chips at this early stage in the investigation, given the amount of gas produced and the time taken, I would expect the graph to be like this:

Safety

*Wear goggles to prevent dangerous substances (such as acid) from entering eyes as it can cause damage to the eyes.

*Handle acid product with responsibility as it is a harmful product and it is corrosive when it meets skin.

*If gas syringe is used instead of gas generator and measuring cylinder, gas syringe should be watched while collecting gas as the syringe may fall out of the end and break if too full.

*Marble chips (small or large) can be inhaled or wedged in body organs or openings

E.g. ears or eyes and this is dangerous.

*Be careful pouring acid into the beaker.

Apparatus

*Measuring cylinder

*Weighing scale

*Gas generator

*Cork

*Stopwatch

*Spatula

*Large, small and powdered calcium chloride chips (25g each)

*Hydrochloric acid (25cm3)

*Goggles

*Trough (or bowl)

Diagram of apparatus used:

INVESTIGATION EXPERIMENT

I was advised to use 25g of calcium chloride. The relative molecular mass of calcium chloride is 111g, therefore the moles of calcium chloride to be used was:

Moles = 25g = 0.2252252 which is 0.2 moles (to 1 significant figure)

111g

I was also advised to use 25cm3 of hydrochloric acid. The acid was added to the calcium chloride and the gas produced was measured every 30 seconds.

Method

First of all I am going to test the reactivity of small marble chips. I measured 25g of calcium carbonate and added them into the conical flask. I measured 25cm3 of hydrochloric acid and put it in the gas generator. I put the cork on the gas generator as fast as I can could and started the stopwatch immediately. After every 10seconds, I record volume of gas in the measuring cylinder. After 3 minutes I took the last reading. After each time I will throw away the marble chips because they cannot be used again as some reactants have been used up. To get the best result I am going to test it two separate times for each size of particles to be able to calculate an average to reduce errors in my work.

Diagram of the experiment

My Result

*Large marble chips

TIME TAKEN

30

60

90

20

50

80

210

240

270

300

330

360

Try 1

0

25

40

55

66

78

88

94

00

08

12

20

Try 2

Average

*Small marble chips

TIME TAKEN

30

60

90

20

50

80

210

240

270

300

330

360

Try 1

8

46

70

88

08

22

34

44

56

60

68

74

Try 2

Average

*Powdered chips

TIME TAKEN

5

0

5

20

25

30

35

40

45

50

55

60

Try 1

02

12

14

16

18

24

28

32

34

34

36

38

Try 2

Average

Analysis of results

To work out the average I added the volumes of both tries and divided them by 2. I have worked out an average because then the results will be evaluated properly and will be plotted on a graph that will give a visual comparison between the sizes of particles. From the results of my experiments I observed that each of the reactions start of fast but start to slow down after some time. I have also noticed that during the reaction the gas generator changes in temperature, as it becomes hotter and this proves that the reaction is exothermic. A reaction is exothermic if heat energy is given out during the chemical change, and the surroundings get hotter3. On the following pages are graphs showing the rates at different surface areas. On each graph at different size of particles, I have both my results to show how they are related to each other by following the same rising pattern. Then on my final graph I have plotted the averages of all sizes of particles. This makes it easier and clearer to compare the quantities of gas for each size of particle.

Conclusion

In this experiment my aim was to change the size of marble chips to investigate the rate at which the reaction will take place and to determine the size of marble chips that liberate the most and the least carbon dioxide gas. I have succeeded in doing so. I recorded the rates of reaction using different sizes of particles. My predictions matched and concluded with my results, as you can tell from the graph, I have proved that the smaller the size of marble chips the more gas is produced at a faster rate because the surface area is more and more collisions take place per second. I also observed that during the experiment the amount of gas produced is fat at the beginning of the reaction, but it slows down towards the end of the reaction, this is because the activation energy (EA) which it had at the start gave a boost to the production of gas and at this point it would have been the fastest, until it had worn off which would be in the middle. The particles of hydrochloric acid (HCl) and calcium carbonate (CaCO3) react by colliding with each other. Although the larger chips are the same mass with the small and powdered chips, it has less surface area.

In the graphs, I saw distinct patterns: they all have positive link that illustrates that they all have the same trend. The graphs are more efficient in describing the same effects as that of the tables because it shows clearly that the smaller the size of particles, the larger amount of carbon dioxide produce and the faster the rate of reaction.

Evaluation

I think my experiment was successful as I was able to obtain the evidence I needed to achieve my aim. I was planning to observe each reaction for 3minutes but I was unable to do so because the reaction using the powdered marble chips lasted only a minute after which it became extremely slow and the reaction seemed to have stopped.

I had a few problems during my experiment. The amounts of gas are not exactly accurate because I had to look at the stopwatch and by the time I looked at the measuring cylinder a second or two might have gone by so they may be estimates rather the exact values. Also at the beginning of each experiments, I had to pour the acid in the gas generator and put a cork on the gas generator. As soon as the acid is poured into the gas generator, the reaction begins and some gas might have been lost. The size of the large and small chips were not exactly the same, each group was made up of chips of approximately equal sizes and this is not exactly accurate. In stirring the experiment one had to be careful of stirring it evenly and not aggravating the reaction.

The experiment could have been improved in various ways. Using beads of limestone can solve the problem of unequal size of particles. Using a magnetic stirrer can be used solve the problem of uneven stirring of reactants. Using a syringe inserted through the cork to add acid to the chips solves the problem of losing gas at the beginning of the experiment. The use of a more accurate scale helps in solving the problem of reading off measurements from the measuring cylinder. Drawing the curves of best fit was an accurate step I took.

My graphs helped in proving my aim, though I got some recurrence in the amount of gas produced during the experiment. A distinctive trend is shown in the graph as clearly show that small particles react faster than large particles.

I was interested in this experiment when I first started. I was interested in seeing changes in the reactants at the end of the reaction. I was very satisfied when I found out that my predictions were correct.

Bibliography

.Heinemann advanced science chemistry by Ann & Patrick Fullick

2.New school chemistry by Osei Ababio

3.Collins GCSE sciences chemistry by Jane Morris