V=10cm³ for excess of acid
Preliminary Experiment:
It took 7.23 min to get 24cm³ of Hydrogen
10cm³ of .5 moles of Hydrochloric acid with 3cm of Magnesium
We will now time for 10cm of gas rather than 30cm, as it takes too long to calculate for 30cm.
List of Apparatus:
Test tube
Test tube rack
Gas Syringe
Rubber bung tube
Metal retort stand
Boiling tube
Stopwatch
Safety glasses
Measuring cylinder
Diagram:
Method:
Collect all apparatus and assemble accordingly (as in shown in the diagram above)
Collect different concentrations of Hydrochloric acid.
Wear safety glasses.
Measure out 10cm of Hydrochloric Acid using a measuring cylinder.
After measuring the 10cm of Hydrochloric acid pour all of it into a test tube.
Quickly drop the Magnesium in the test tube.
Then cover the test tube with a bung as soon as possible.
Record the time taken to get 10cm³ of Hydrogen using a gas syringe.
Record the results in a table.
After recording the results repeat the experiment.
As there are 5 different concentrations (.5, 1, 1.5,2, 2.5) the experiment must be done 10 times including repeats.
Variables:
The concentration of the Hydrochloric acid will differ between each experiment.
We will be using 5 different concentrations.
Constants:
We will be keeping the same apparatus so as to keep it a fair test.
The volume of Hydrochloric acid will maintain the same within each
Experiment.
The temperature will be maintained constant so to make sure that each that the reaction is not affected by it.
The fact that we will not shake or stir the Hydrochloric acid shall be kept constant as this would make our results unreliable.
The weight and size of the magnesium ribbon will be the same through out the experiment.
Results Table:
Analysis:
Conclusion:
The graph shows that as the concentration is increased so is the reaction rate.
As the Concentration doubles the rate of reaction does not. This is proven with in the graph. As with .5mol of concentration the rate of reaction is.0078. If we double the concentration then we will expect that the result that we got with the .5mol of concentration to have doubled as well. But the result for the 1mol concentration was only .07, which in fact; it is nine times bigger than the results of the .5mol concentration. But as we double the concentration to 2mol concentration it is obvious that this time it has not becomes nine times bigger. But is only almost three times as big. This suggests that not all of the results were accurate or that as you keep doubling the concentration then the difference between the results gets less.
The results on the graph show that my prediction was both correct and accurate as I stated that an increase in Hydrochloric acid would lead to more successful rate of reaction is shown by the increase in the curve of the graph. The graph shows a gradual increase followed by a sudden increase and I also found out that if you double the concentration then the rate does not necessarily double as well.
At .5 Conc. mol/dm³ the rate of reaction was. 0078
At a greater concentration 1 Conc. mol/dm³ the rate of reaction was. 0700
This proves that as the concentration goes up so does the rate of reaction.
Evaluation:
Overall I was happy with the way that the experiment was done and constructed as it was done with caution and accuracy, but with this said I found an anomaly in my results. The anomaly was in the 2 mol/dm³.
It took exp. 1 2.93 seconds to make 10cm³ of Hydrogen
It took exp. 2 2.08 seconds to make 10cm³ of Hydrogen
The difference is .85. This means that there is 34% error and so only 66% accuracy in this experiment.
In my opinion I think that human error was the cause of this anomaly to have occurred as the human eye and hand co-ordination are often not correct and can cause the results to be slightly wrong. Also the speed at which the bung covered the test tube would have affected our results as hydrogen might escape causing the results to mislead. Another cause of the anomaly could have been that the gas syringe was not at zero meaning that the amount of hydrogen needed would of reached it’s 10cm to quick and so again would of effected our results. Overall I think that out results were reliable since we repeated the experiment twice so as to minimise the risk of more anomalies happening. I think that if the experiment were carried out in a more controlled environment. By controlled environment I mean things such as light can’t effect our results as much as well as temperature of the room shall have to be kept constant. If we did the experiment in a more controlled environment where such factors can’t affect our results as much then it would improve the experiment and the results. Also if the bung fitted more easily into the test tube assuring that it would be placed with more ease and therefor reduce the risk of anomalies. If an alternative experiment were carried out then I would time how long it takes for the whole of the magnesium strip to dissolve in each of the concentrations used. The last improvement to my procedure is that I should check for gas leakages where the bung is placed into the conical flask, a smear of Vaseline would help me do this. This would there for improve the accuracy of my results, as their would be a more accurate reading from the gas syringe.
