Equipment: Gas Syringe, Timer, 100 cm3 beaker, clamps and stands, delivery tubes, 100 cm3, conical flask.
Method:
Step 1: Set up the equipment, then measure out the correct volume of acid to water, which will vary, and measure out the correct length of Magnesium ribbon, this will ensure the test is fair.
Step 2: Place the Magnesium ribbon in the conical glass, pour over the water/acid solution and start the timer, record the amount of gas produced every 30 seconds for 5 minutes, e.g. 30, 60, 90, 120, 150, 180........seconds etc.
Step 3: Record the results in a table, then once the 5 minutes has expired, change the ratio of Hydrochloric acid/water, for example instead of putting 25 cm3 of water and 0 cm3 of acid, change it to put 20 cm3 of water and 5 cm3 of acid, this will make it a fair test because it has the same overall volume but a lower concentration of acid. Repeat this process.
Preliminary
Results: The original method that I did was flawed in some ways, so after doing some preliminary results I decided to alter the method so that the experiment would be fairer. As the preliminary results show, 2 minutes is not enough time to get the results needed, so it was changed to 5 minutes. Also the length of magnesium ribbon used was too long, which either made the reaction go too fast with a high concentration or the reaction went on for too long with a lower concentration.
Results:
Concentration of Acid = 1 Mole
Key:
Conc. = Concentration
R.T = Room Temperature
Mg = Magnesium
Graphs:
Conclusion:
From the results I can conclude that my prediction was correct. The higher the concentration of acid the faster the rate of reaction. This is shown visually in the graphs, when the concentration of Acid is higher the Magnesium reacts a lot faster and gets to a stop much quicker. As the concentration of acid goes down it starts the reach a stop slower, and in the end doesn’t reach a stop in the time given.
Analysis:
The results are reliable because they both show effectively the same thing: that the Acid reacts with the magnesium and produces gas at different speeds, depending on the concentration of acid, and then whether it is at the start or not within the time limit the gas will stop being produced. The results can also reliably show how the temperature affects the rate of reaction; the results show that on one day when the temperature was lower (20°C) the reaction slowed down, and on the day when it was hotter (24°C) the reaction sped up. Although the change in temperature was unexpected it was still recorded on both days, and the anomaly was explained. A way that could provide addition relevant evidence is to take another set of runs, but instead take 3, each one at different temperatures. This would effectively show how temperature and concentration can affect the rate of reaction.
Evaluate:
The results taken show what were expected to be shown; although some anomalies did occurred. The first result of the second run was taken at a different time than the rest of the results from the second run, and as shown on the table, on the two separate days the room temperature was different. It therefore shows a more similar pattern to the results in the first run than the second run. There were only 2 runs taken, because the results from the first run were so successful and went so smoothly I thought a second run would only further show what I already knew, just make it more certain and reliable. This was so, except I didn’t expect the change in room temperature to affect the results as much as it did, it doesn’t make the results any less certain; it just shows how much the temperature can affect the rate of reaction. I recorded the results every 30 seconds for five minutes because I believed that five minutes was enough time for the reaction work fully, which in the higher acid concentration cases it was; I took results at 30 second intervals because this was enough time for a sufficient amount of gas to be produced, making it a fairer test. If I could have repeated this experiment again, I would have taken 3 runs with different temperatures for each, to show how much the temperature can affect the rate of reaction.