Diagram.
Method.
- A range of the different concentrations of hydrochloric acid was prepared.
- The apparatus was set up as shown in the diagram above.
- 50cm3 of each of the solution was measured using a measuring cylinder then poured in to the conical flask.
- 3grams of marble chips were weighed out using a balance.
- The marble chips were then swiftly added to the solution and the bung was placed inside the conical flask.
- The stopwatch was started and the reading from the measuring cylinder was taken every 30 seconds.
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After every 30 seconds the amount of CO2 released was recorded by looking at the measurement on the measuring cylinder.
- This was done for 180 seconds so by the end of the experiment 6 readings were obtained.
- The experiment was carried out in the same way, only the concentration was changed, a less or more concentrated solution was used but the total volume of the solution remained the same.
Fair Test.
- It was made sure that the marble chips were of similar size, and they weighed 3grams-If these varied then I would expect the results to be inaccurate and so my experiment would be of little use.
- The same amount of hydrochloric acid was used each time-to ensure that no anomalies would occur because if I accidentally added more solution then there would be more collisions due to the increase in the number of particles and therefore I would obtain anomalous results.
- I took readings at the same time intervals throughout the experiment i.e. a reading every thirty seconds in all my experiments-this was also important because if the experiment was left for longer then the reaction would have more time to take place therefore the results obtained would have been anomalous.
- All the experiments lasted for 180 seconds.
Safety.
- I wore safety goggles throughout the duration of the investigation.
- Extreme care was taken when handling the acid ensuring that the acid was not spilt. It was also made sure that there was nothing near the experiment that could cause an accident or be damaged if an accident did occur.
- In this experiment I had to make sure that I was careful with all glassware in case it broke, because if it did I had to be prepared to clean up the spillage immediately.
- I also had to be careful especially with the stronger concentration of acid because as it was corrosive, and I had to make sure that it did not come in to contact with my skin.
- Most importantly we have to take general care and active awareness when we were carrying things around. We had to walk around the lab and be aware of the space and dangers around us e.g. tucking our stools under the desks.
Results.
Conclusion.
From looking at my results and graphs I am able to conclude that the more concentrated the acid the quicker the reaction takes place and the more gas was produced. As we look at the graphs we can clearly see that in all five experiments at the beginning, the reaction happened more quickly than at the end where we can see that it started to tail off.
From these results we can conclude that by increasing the concentration of hydrochloric acid the rate of reaction is increased. This can be seen as the highest concentration had the highest reaction rate and reached a maximum of 90 cm3, where as the lowest concentration only reached a maximum of 18 cm3 at the end of the three minutes. The increase does seem to be proportional, as the gradient of the line seems to increase by roughly the same amount each time.
Before I did the experiments I predicted that the more concentrated the acid was the quicker the reaction would happen and more carbon dioxide would be produced. This was found out to be completely correct.
This is due to the ‘collision theory’ because as you increase the concentration of the acid you are increasing the number of hydrochloric acid particles present so in theory you are increasing the chance of a collision happening and it was found out that this was true because the higher the concentration got the quicker the reaction happened.
At this point we are able to answer our main aim, which was 'how does changing the concentration of acid affect the rate of reaction between hydrochloric acid and marble chips’. The answer to this would be that increasing the concentration of the acid would increase the rate of reaction.
Overall this was a very successful experiment and everything went very smoothly, and that was why my results were very good, and I am able to make a conclusion like this.
Evaluation.
The experiment proved to be a success and I retrieved reliable results from which I was to able to base strong conclusions. The results were as expected. Although there was space for improvement the resources available for the experiment was limited, therefore I was not able to use sophisticated devices.
The whole experiment had remained a fair test, which helped in getting good results.
There were a couple of points for the experiment to be improved by, firstly by adding the marble chips and placing the cork on top lost time and some of the immediate reaction was lost. The timing was not very accurate, because some of the experiments were left for longer, this obviously increased the error percentage in the results making the result outcome slightly incorrect. The marble chips were also an inaccuracy because some chips were bigger than some so adding to the inaccuracy of the experiment.
If I were to repeat the experiment I would find a more accurate way of timing the experiment and also find another way that would ensure that none of the gas would escape. In addition I would also find a more accurate way to weigh the chips and the volume of the hydrochloric acid because the volume of the acid and weight of the marble chips, were not the same for each experiment. I also would use powdered marble because it would mean that the surface areas would be more or less the same.
To extend this experiment I would repeat this experiment and also I would try using another reactant instead of hydrochloric acid I would use for example, sulphuric acid. I could also try using something else instead of the marble chips, which would be interesting.
