Investigating Factors that Affect the Rate of Reaction Between marble and Dilute Hydrochloric Acid

Investigating Factors that Affect the Rate of Reaction Between marble and Dilute Hydrochloric Acid
The local Council are concerned about the effect of acid rain on the marble statues in the local park. Investigate a factor that affects the rate of reaction between marble (calcium carbonate) and dilute hydrochloric acid. There are three main factors that affect the rate of reaction. These are: Particle size Concentration Temperature With investigating any of these, there are slight problems which make them not as reliable as they could be. With particle size, it is extremely difficult to get control of the sizes, e.g. large, small, medium. I will not be investigating this as it is very unreliable. With concentration, even though it is easy to control by measured dilution, the room temperature affects the reaction rate, and is hard to control. If the experiment needs two lessons to be completed, the room temperature is unlikely to be the same, therefore affecting the results and making it unreliable. I will not be investigating concentration either. I will be choosing to do investigate temperature. It is difficult to get fine control without water baths or thermostatic heaters, so the results will be unreliable because of this. However, I plan to tackle this problem by putting the marble and acid on the tripod as soon as the temperature we are trying to investigate is reached, and if the temperature falls I will put the Bunsen burner under the tripod again to try and reach the temperature.
Prediction -???- The collision theory is that for a reaction to occur, particles must collide with each other. An increase in the temperature is an increase in the energy of the particles, and anything that increases the energy, and therefore the frequency of the collisions, will cause an increase of the reaction rate. I predict that when I increase the temperature, the rate of reaction will increase. This is because when I increase the temperature I am giving the particles more energy, and this will increase their speed and will therefore collide more often into each other, increasing the number of successful collisions, and causing an increased rate of reaction. Apparatus For my experiment, I will need:
A Bunsen burner to heat up the acid
1g of marble chips, this is enough to get good results (a
difference between the different temperatures results), but not
too much so it takes too long to finish reacting
30cm of acid. I chose this amount because it is enough for the
marble chips to complete their reaction.
A spatula and scientific weighing scales to measure and get an
accurate amount of marble chips
A large beaker to hold the acid and marble chips on top of the
tripod. I will be using a large beaker so that the heat doesn?t
escape easily, and can get more accurate results.
Heat proof mat
Stopwatch which records time to 1/100second to get more accurate
results
Tripod
My apparatus will be set up like this: Safety
Goggles
Hair tied back
Stools tucked under desks
Method I am going to time how long it takes for 1g of marble chips to dissolve in 30cm of acid. I will set up the apparatus as shown before. I will time the reaction rate at the following temperatures: 10 C 20 C 40 C 60 C 80 C I will record each time in a table. I will do three attempts at each temperature and make an average. I will then use the average to work out a reaction rate ( grams/sec) Fair Test To make my test a fair one, in every attempt, I will keep the mass and particle size of marble the same (1g, powdered marble), the concentration of the acid the same ( 2M), and will only change the temperature for the purpose of the experiment. I plan to do three attempts and make an average, and repeat any results which are clearly anomalous ones. Actual Method In the actual experiment, I decided to change the concentration of the acid from 2M to 1M, as the marble powder reacted too quickly with the stronger acid, and the results were too similar to each other. Results Temperature oC Time to React (seconds) Average (seconds) Rate (grams/sec) Trial 1 Trial 2 Trial 3 10 94.04 98.22 84.81 92.12 1¸92.12 = 0.010855405 20 37.28 42.44 40.07 39.91 1¸39.91= 0.025056376 40 28.53 22.91 27.12 26.19 1¸ 26.19 = 0.038182512 60 14.16 16.25 17.35 15.92 1¸ 15.92 = 0.083892617 80 10.09 12.60 10.32 11.00 1¸11.00 = 0.09090909 The stopwatch was used to 1/100second. This justifies itself as the results in the different trials were quite different sometimes, so it helped making the averages more accurate. Also, the averages needed to be accurate as they were all under 1second. Analysis My results tell me that as the temperature increases, the rate of reaction also increases. This shows that the collision theory applied to this experiment, as the rate of reaction increased due to the temperature rising and giving the particles more energy, resulting in them having more speed and more collisions. This increased the rate of reaction. My prediction was correct as I predicted that the rate of reaction would increase as I increased the temperature. Conclusion -???- As I increased the temperature, the rate of reaction increased. E.g. at 10 C the rate of reaction was 0.03g/s, yet at 80 C it was 0.09g/s. This shows that at 10 C, the energy of the particles was lower, than at 80 C, as the rate of reaction was 0.03g/s, compared to 0.09g/s. Yet again, this shows that my prediction and the collision theory is correct. Evaluation I think that my results were quite accurate, but could have been improved, though I did the best experiment I could for the equipment which was available to me. The quality of them were good, as I they backed up what I predicted, and made sense as they showed the collision theory was happening during this experiment. The accuracy of the results could have been better, as I had some trial results which were not similar to the others. If I had of repeated these, then I might have got a more similar result to the other trials, making the average overall more accurate. Also I was not always sure when the reaction had been completed, affecting the time in some cases. With the experiment, I was pleased with the temperature, as it hardly changed at all during each trial. This made my results more accurate. One problem I had was seeing when the reaction had stopped, as I could not always tell when the reaction had fully stopped, which resulted in me sometimes stopping the stopwatch too early or too late, making my results less accurate. My results were not as good as I had hoped, as I knew they were not accurate as they could have been. I was hoping for more similar results with all the trials, so I knew that my averages were more accurate. With the anomalous result for 10 C, I think that this was due to the fact that the 10 C was not very reliable, as we had to cool it down beforehand, and we found it very difficult to keep it at the temperature. I also think this may have been due to the fact that the particles did not have much energy at all at this temperature, also making the reaction rate a lot slower than the rest. We could have improved this experiment by using water baths, as this would have kept the temperature the same throughout the experiment. This would have made a great difference to the results as it would have made the results quite a lot more accurate. I could have improved the reliability without the water baths, by doing more trials, and repeating any that are obviously not correct and would change the overall average, and making the experiment a lot less accurate. Planned experiment I will plan a second experiment, also on temperature. This second experiment is planned to give more accurate results. Apparatus
1g of marble chips, this was shown to be a sufficient mount in the
last experiment
30cm of acid. This amount was a good amount in the last
experiment, as all reactions finished with acid to spare.
A spatula and scientific weighing scales to measure and get an
accurate amount of marble chips
One water bath
A thermometer to check temperature
A stopwatch which records time to 1/100 second
A beaker to hold the acid and marble
Method I am going to time how long it takes for 1g of marble to dissolve in 30cm of acid. I will put the acid and the marble powder in a beaker and will use a water bath in the experiment for the heat. I will time the reaction rate at the following temperatures: 10 C 20 C 40 C 60 C 80 C I will record each time in a table. I will do five attempts at each temperature and make an average. I will repeat any anomalous readings. I will then use the average to work out a reaction rate ( grams/sec)

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