Apparatus- Sulphuric acid (molar 1, 2, 3)
Magnesium ribbon (1cm each experiment)
Water
Stop clock
Conical flask
Two measuring cylinders
Safety goggles!
Diagram-
Safety- for safety reasons, goggles must be worn to protect you from the harmful acid. All the apparatus must be paced on the work bench and not close to the edge as to fall on the floor. Lab coats should also be worn to not get any chemicals on your clothes.
Method-
- A preliminary experiment was done first of all and the results were recorded, using 10cm³of Sulphuric acid and 15cm³ of water.
- I will first collect 15cm³ of Sulphuric acid (1molar) in one measuring cylinder and 10cm³ of water into another measuring cylinder
- Both the Sulphuric acid and water will be poured into a beaker
- A 1cm strip of magnesium ribbon will be cut
- As soon as the magnesium ribbon is dropped into the solution, the stop clock will be started
- When the magnesium ribbon has completely disappeared, the stop clock will be stopped
- The time will then be recorded
- The solution will then be poured away
- This same experiment will be done twice more with the same amount of 1 molar Sulphuric acid and water
- The experiments should then carry on with 20cm³of Sulphuric acid + 5cm³ of water and 25cm³ of Sulphuric acid and 0cm³ of water.
- After these experiments are done with 1 molar of Sulphuric acid, they will be repeated with 2 molar and 3 molar, until the experiment had finished.
Preliminary test results-
Modified plan- After doing my preliminary experiment, I realized that the concentrations made the reaction a lot slower than we expected. Therefore we needed to change the concentrations to more appropriate ones. Each molar of acid is experimented three times and then averaged so a graph can be plotted. This makes the results a lot more accurate than just doing the experiment once or twice each. For each molar of acid i.e. 1, 2, 3 will be using the following concentrations:
15cm³ acid + 10cm³ water = 25cm³
20cm³acid + 5cm³ water = 25cm³
25cm³acid + 0cm³ water = 25cm³
The same amount of magnesium ribbon (1cm) will be used for each experiment. Also the same measuring cylinders and conical flask will be used/ I will make sure that the water and Sulphuric acid do not contaminate each other in the measuring cylinders.
Results table-
Averages-
Analysis- After performing the experiment we found a method which could tell us the actual concentration of acid we were using after diluting it with the water. To work this out we used the following method:
Volume of acid x Number of molar used
Total volume
After obtaining this formula, we then worked out the concentrations for each experiment, here are the results:
From all my results I can say that as the concentration of Sulphuric acid used was increased and the molar of acid used was increased, the time it took for the magnesium ribbon to disappear was quicker. We can see this from looking at the tables. I decided to draw two different graphs, one showing the relationship between the acid and the average time, and another to show the rate of reaction of the experiment, to work the rate of reaction out, you do one divided by the average times.
For example... 1
Average time (secs) = Rate of reaction
Here is a table showing the results of the rate if reactions:
From the graphs, we can definitely see that the relationship between the acid and the rate of reaction and the acid and the average time. In both graphs it is showing a definite increase in speed as the concentration increases and the rate of reaction also increases. This coincides with my prediction as I predicted that this was going to happen. As there are more acid particles moving around therefore the collisions can be more frequent.
Evaluation- Having finished the experiments and drawn up my results and conclusion, I have realized that there were certain things I could have changed or improved on. For example I could have used another molar, or have done different volume totals and compared them to each other. I could have made sure that the stirring was kept constant throughout the experiment. Another person could have double checked that all the 1cm strips of Magnesium ribbon were cut to the same length as it could have affected the reaction times. Other than that, I am happy to say that the investigation went pretty well.
Although I did find that I had one anomaly which I could profoundly see from the graphs. The concentration for this specific anomaly was;
15cm³ of Sulphuric Acid (3 molar) + 10 cm³ of water. This could have bin due to the lack of stirring or maybe one of the measuring cylinders became contaminated.
My results were reliable as I had done each experiment at least three times and had averaged out the times to be then able to plot two graphs. I think that the results are sufficient enough support the conclusion as there weren’t any major problems other than the one minor anomaly, which can b re-done to see whether I can obtain better results.
Next time, I could try changing the concentrations of the acid making it either higher or lower, which would obviously change the volume. I could also change the temperature by itself, or change both the concentration and the temperature to see what effects that would have on the results. In conclusion, I am very happy with my investigation as it has produced very good results, and has proved my prediction.
