I will be keeping these factors the same:-
1) Amount of marble chips (5g)
2) Combined amount of acid and water (50ml)…. (However the ratio if these 2 will change)
3) Size of marble chips
4) Temperature of acid (30oC)
5) Same size conical flask
6) Volume of gas to be collected (15ml of CO2)
I will change this factor:-
1) Acid content in the 50ml (I will change this 4 times)
When the marble chips react with the hydrochloric acid it gives off CO2 up the measuring cylinder. I start timing when the acid is added with the marble chips and when I have collected 15ml of CO2, I stop the clock.
I predict that the more Hydrochloric Acid present, the quicker the rate of reaction. I base this prediction on the collision theory because from that, I know that the more concentrated the acid, the more molecules present hence the more collisions. This in turn will increase the Activation Energy Level which causes more reactions and all this will ultimately result in a quicker reaction. My trial run and common scientific knowledge helped me make this prediction.
I will make 6 measurements will the following acid/water concentrations.
0/50 10/40 20/30 30/20 40/10 50/0
For the first ratio for example, I will be using 50ml of acid and 0ml of water.
1I will try to ensure my experiment goes to plan and that I have no problems or accidents. I will try to stop the clock exactly when it reaches 15ml of CO2. I will try and use marble chips that are of the same size and shape. This is vital because a bigger piece with a different shape may have a bigger surface area which means it will react quicker. Therefore, I will have to be consistent in choosing marble chips which are identical throughout the experiment
IF my results do not match my prediction which, is backed up with scientific knowledge, I will share results with others to see where I may have gone wrong. I will repeat the experiment once and then use both sets of results for averages.
Before I started my experiment, I did a practice run to get a feel of what I would be doing in my real experiment. I found that the more acid present, the quicker the reaction. This has helped me to plan my prediction because I now know what to expect for the final outcome.
Obtaining
I performed a safe test with no problems or accidents occurring. I collected 2 sets of results which I put into a table.
I tested 6 different concentrations and I have 2 results for each concentration.
Here are my results for the 6 different concentrations:-
Water/Acid
The first row represents the water/acid measurements.
The second row represents the 1st set of results.
The third row represents the 2nd set of results.
The fourth row represents the averages taken from both sets.
The time is measured in seconds.
The measurements are taken in ml.
I repeated this experiment once to get 2 sets of accurate results. However, I noticed that both sets are very similar which shows the accuracy I took with the experiment. They also back up my prediction so I feel no need to share any results with other people. I made sure I used the exact same amount of acid each time. I also made sure that I used the same size (5g) and shape marble chip for the reasons I said above I my planning. However, I realise that I cannot exactly get 5g but I made sure I got as close as possible.
Analysing
In my experiment, I have found that the reaction is quicker when there was 50ml of acid and 0ml of water which backs my prediction up perfectly.
I made 3 graphs with the results I recorded and on my graphs; you can see that as the water increases, so does the time. This is apparent in all 3 graphs and it means that as I add more water, the rate of reaction is slower because I am taking HCL molecules away which slows the rate of reaction down. This fits in with my prediction and the collision theory because I have more acid molecules to react with meaning the reaction will be quicker.
From scientific knowledge and my results then, I conclude then “that the more acid present in the acid/water ratio, the quicker the rate of reaction”.
Here are the 3 graphs, 1st set, 2nd set and 3rd set (averages)
Evaluating
I think that the investigation was a success because I have received accurate results without any accidents or mistakes. My results fitted in with what I expected to happen which was obviously helped with my trial run at the start. I believe the evidence I collected was accurate and as best as I could. As I stated before, there were no results that stood out in my tables which show my accuracy in this experiment. I believe my careful and planned method was responsible for these accurate results and I think I have investigated the question quite well. However, if I had the chance, I would have maybe added more results to my method, i.e. maybe seeing how long it would take with 80ml, 100ml and even 150ml of acid. In doing this, it would have given me a wider set of results but I believe my 5 separate results were sufficient to support my prediction. I think my results support my conclusion because they both state that as I add more acid, the rate of reaction quickens. My results are reliable and I received no anomalous results. I believe this reflects on the effort I put into the investigation. One interesting thing that I noticed was that as the reaction started Hydrochloric Acid near the chips would have been depleting which means that the concentration of the acid around the chips would be less than average. One way of solving this would be to constantly stir the acid around covering the chip with new acid all the time.
