As soon as the magnesium has visibly disappeared I will stop timing and record the time in seconds by using a table.
This is what the table will look like: -
To make the experiment as accurate as possible, I will ensure that the length of each piece of magnesium is exactly 1cm in length. Also keeping the total working volume at 25cm3 (no more/less) and at the same room temperature so the temperature would not act as an accelerant to increase the rate (one of the factors that can affect it, as previously stated in the collision theory) of the reaction. By using the same stopwatch I would be able to ensure that the time is constantly being recorded by using the same mechanism, not one that may be slightly faster than another.
To further increase the accuracy, I plan to repeat the experiment at least three times but due to time restrictions for doing this experiment the minimum amount may have to be restricted to carrying out the experiment only twice.
To work out the dilution (concentration) I use an equation: -
Concentration = Volume of Acid x 2(M)
Total Volume
Or
Concentration = 2(M) x Volume of Acid
25 (cm 3)
So by using this equation the concentrations would be: -
The reason for me leaving the times unrecorded for the last set of results (acid = 0cm3, H2O = 25cm3 etc.) is due to the fact that there is no acid, because of this the reaction would hardly happen at all due to there only being water. The reaction, If any, would take a long time to be noticeable and so I thought it necessary to leave that set of results due to my previous knowledge of oxidation and the amount of time it takes to occur.
Obtaining evidence
The following tables show the results of the experiment: -
To find out the average of both times to get the most accurate result possible I simply add together the two separate times (s) and divide by the amount of data there, so in this case it would be two sets of data (the two times).
If I do this for all the separate results this is the complete table of results that I am left with: -
I now plan to interpret this information into two graphs, Concentration vs. Average Time and Concentration vs. Average Rate.
To do this I will have to find out what the rate of the reaction is.
I will do this by using another equation, this time it is: -
Average Rate = 1
Average Time (s)
By using this equation I will have to alter the table of results by adding two more columns (rounded to 4d.p): -
The test has been made fair by using the method stated in the Plan. I have used the same length of magnesium for every result and I have also used the amount of acid and water as accurately as possible.
The graphs clearly show that as the concentration of the acid in the solution increased, the average rate decreased. This shows that my prediction was correct, I stated that as the 'concentration of the hydrochloric acid increases, the average rate of the reaction will decrease until it will be almost unnoticeable when the concentration reaches 0.0.' The first graph (concentration vs. average time) shows that the reactions take longer to occur due to the decrease in concentration, if the time increases then this must mean that the rate is decreasing due to the lengthening amounts of time that it takes as the graph progresses. The second graph (concentration vs. average rate) proves my prediction even more accurately than the first, as the concentration decreases do does the average rate of the reaction.
The results that I gathered for the experiment turned out almost exactly as I had predicted. I noticed that the results increased almost seven-fold as the length increased. The reading at 0.8M (concentration vs. average rate) was 0.035 (-2) and the 1.6M reading was 0.250(-2).
The results showed that the prediction that I made earlier was accurate and corresponded to what I thought would happen very well. There were two anomalous results at the start that I re-tested due to them being an obvious error. This could have happened due to my own carelessness, by not measuring the contents accurately; or by not mixing the solution so that the outcome would be taken due to the acid not being diffused etc.
Evaluating
The method that I chose to use for the experiment proved to be a very accurate and successful way of carrying out the experiment due to the outcome of the results that I took. The results that I received from doing the experiment in this way were, in my opinion, very accurate although there was a few anomalous results concentrated at the start of the experiment (as explained in the Analysis).
The accuracy of the experiment has been shown in the graph’s, all have turned out as I had predicted them to. This shows that the method is trustworthy and must also be a good enough method to set my theory against.
The graph’s seem to show a steadily increasing/decreasing trend. Although I feel that the experiment was carried out in the fairest way possible, I also feel that there also could have been a few slight changes to make the results (and graphs) more accurate. There are other methods finding out how different properties affect the rates of reactions.
I could have used Hydrochloric Acid and Marble Chips to show how the surface area of the reactant (in this case the marble chips) affects the rate. I could have also used Sodium Thiosulphate and Hydrochloric Acid, they will react to form a yellow precipitate of Sulphur (repeated at different temperatures to see if the rate has increased [at different temperatures the colour will change faster signalling faster reaction rate]). Finally I could have measured the decomposition of Hydrogen Peroxide to see how different catalysts affect the rate. If you add maganese (IV) oxide catalyst (can be found in potato skins & blood) these work as a catalyst, you then measure the amount of Oxygen that is given off by using a gas syringe (the faster the oxygen is released, the faster it is reacting). These are a few ways to find out how different conditions can affect the rate.
The method that I chose to use gave a reliable set of results, which helped to prove that my theory was correct. As long as the procedure that I stated in the Plan is followed I see no problem with it being used accurately and fairly in the future if a re-test was to be carried out.
The few 'mistakes' that occurred during the experiment could have been due to my own carelessness, by not measuring the contents accurately or by not mixing the solution so that the outcome would be taken due to the acid not being diffused equally etc.
From the evidence that I have gathered by doing this experiment I believe that I can draw up a valid conclusion.
I have discovered that the Collision theory plays a major part in understanding what elements affect the speed (rate) of the reaction. The Collision theory describes perfectly reaction rates. The theory states that the rate of a reaction depends on how often and how hard the reacting particles collide with each other. This therefore means that depending on the amount of collisions and the force that is put behind them depends on the speed of the reaction. There are several ways of increasing the rate of collisions (temperature etc.); the one that I planned to use was to decrease the concentration of the hydrochloric acid and water (Hydrogen Oxide) solution. If the solution was more concentrated it means that there are more particles of hydrochloric acid between the water molecules, which makes collisions between the particles on the magnesium more likely due to the increase of reactant's (hydrochloric acid) particles. Using this theory I have proven that my experiment has worked and that my prediction was accurate. I feel that if I had gathered some more results from the experiment then I would have got a wider and more accurate set of results. But even with these extra sets of results I am sure that the graphs would not have changed their trends or shapes to a great extent.
On the whole I feel that the experiment went well, with accurate readings and correct results, giving me good results for an accurate and clear conclusion.
![The Effect of Concentration on the Rate of Reaction between Magnesium [Mg] and Hydrochloric acid [Hcl]](https://mbt-essays-prod-public.s3.eu-west-1.amazonaws.com/934664/listing/934664_1.jpg)
