In figure two when the particles will be given Activation Energy there is a much higher chance than figure two of collisions as the concentration of Hcl is much higher than in figure 2. This would mean more particles moving around in the same space and that means more chances of a collision, in which two particles will join and form a new substance. In figure one the opposite of figure two will happen. Because there are less particles of Hcl there is less chance of a collision, as there will be less particles of Hcl moving around in that space, after they have been given Activation Energy.
This means the Higher the concentration; more chances of a collision and faster the reaction. The more lower the concentration, the less chances of collision and slower the reaction.
Prediction:
Based on my scientific knowledge and based on my two diagrams explaining the chances of a collision in Low concentration or higher concentration, I predict that, when I put the same amount of Magnesium (Mg) in Low and High concentration of Hydrochloric acid (Hcl), there would be a much slower reaction in the Low concentration of Hcl with Mg, in comparison to High concentration of Hcl with Mg. The amount of Mg I put in both of the Hcl (High and Low) would be same, as not keeping it same would mean a completely wrong experiment. The reason for my prediction as pretty obvious, because as my scientific knowledge shows, in Higher concentration of Hcl there is more chance of particles with Activation energy colliding and starting a reaction as compared to Lower concentration of Hcl. I also predict that as we increase the concentration of Hcl, starting from 0.25 molar to 1.50 molar, the rate of reaction will increase rapidly as the particles of Hcl in that same space increase and therefore that means more collisions, more joining of particles and new substances been made.
Equipment List:
- Hydrochloric acid (Hcl) starting from 0.25, 0.50, 0.75. 1.00 And 1.50.
- Magnesium (Mg) ribbon, each one 4cm in length.
Fair Test: To keep this experiment simple, easy and conclusive I will have to make certain changes to keep this experiment fair, and I will have to keep certain things same throughout the whole of the experiment, so that I get the information out of this experiment.
Things I will keep the same throughout the experiment.
- The length of Magnesium (Mg) must be kept at 4cm however many times the experiment is repeated and no matter what.
- The volume of acid must be kept at 40cm³, no matter what and however many times the experiment is repeated.
- After finishing the test of every concentration of Hcl, I will push the syringe all the way in, so that all the Hydrogen gas gathered this time comes out, otherwise it will get mixed with the Hydrogen gas of the next concentration and show the reading on the syringe which is more than expected and incorrect.
- The whole of the experiment must be conducted at roughly room temperature, which is 21°C.
- We must collect the Hydrogen gas for only 30 seconds; each time a piece of Magnesium (Mg) is put in Hydrochloric acid (Hcl).
Things I will have to change in order to get the desired and correct results.
- The concentration of Hydrochloric acid (Hcl) will start from:
0.25 Molar – Lowest Concentration
0.50 Molar
0.75 Molar
1.00 Molar
1.50 Molar – Highest Concentration
Safety: This experiment is not a ‘game’ and not doing this experiment correctly and misusing the equipment could result in unnecessary and avoidable injuries.
- We have to be careful when dealing with the concentrations of Hcl, as it is damaging to the living tissues. If I do manage to spill some Hcl on my hands, than I must wash my hand thoroughly with normal water under the tap.
- We must wear safety glasses all the time during this experiment, as this experiment involves Magnesium (Mg) reacting with Hydrochloric acid (Hcl).
- We must keep Magnesium (Mg) away from Hydrochloric acid (Hcl) while we are preparing the next test, because if Mg comes in contact with Hcl before you want it come in contact, than there is a risk of injury.
- For safety we must make sure that the clamp holding the Ground Glass syringe is tight enough.
- We must be careful when pouring Hcl in to the measuring tube, as the bottles are made of glass, which makes them heavy and slippery.
Method:
The method I choose to proceed with an experiment to find whether the concentration has any increasing or decreasing effect on the rates of reactions is quite simple. This experiment calculates the rate of reaction by looking at the amount of gas produced in a given amount of time. To proceed with the experiment we need the following items listed under the section Equipment list. This experiment is quite simple and easy, although wearing of safety glasses is advised, as this experiment involves Hydrochloric acid (Hcl) of different concentrations starting from 0.25, 0.50, 0.75, 1.00 and finishing with 1.50 molar in concentration. To start this experiment I will first measure 40cm³ of 0.25 Hcl by using a measuring Cylinder and pour it in a conical flask. I would then do a check on the syringe to make sure that it is all the way in, because if it is not in, then the whole experiment could go wrong because it would give us the wrong information. I will also check that the stop watch has been reset, so that the time starts from 0. After doing the check I will connect the cork and the bent tube with ground glass syringe and get ready. If we have to do this experiment accurately, then we need two people for this. After connecting the cork and bent tube to the Ground glass syringe I will add 4cm of Magnesium to Hydrochloric acid in Conical flask and as soon as I have added Magnesium, I will quickly close the Conical flask, with the cork connected to the bent tube and my other partner will start the time as soon as the Magnesium is added to Hydrochloric acid. After 30 seconds on the stop watch, I will disconnect the cork with bent tube from the conical flask, so that no more Hydrogen gas (which is given off, when Hydrochloric acid reacts with Magnesium) passes from conical flask into Glass Ground syringe. We will calculate the rate of reaction of 0.25 Hcl with 4cm of Magnesium by measuring the volume of Hydrogen gas which managed to collect into the Ground Glass Syringe within 30 seconds. I would then record the volume of Hydrogen gas into a Table of results. I will repeat the experiment with 0.25 Hcl and 4cm of Mg three times, so that I can find an accurate average volume of gas which was collected in the syringe when 0.25 Hcl and 4cm of Mg reacted.
To find if the rate of reaction increases as the concentration of acid goes up, I will repeat the same procedure which I used to measure the rate of reaction of 0.25 Hcl with 4cm of Mg. However, this time I will swap 0.25 Hcl with even more concentrated 0.50 Hcl. I will then do my usual checking on syringe and stop watch and wash the conical flsk thoroughly with clean normal water and dry it up with a piece of cloth. After that I will let the experiment proceed normally with everything except the concentration of acid being changed. I would repeat this experiment three times as well to get an accurate average of the volume of Hydrogen gas in Ground glass syringe. After finishing the experiment to calculate the rate of reaction of 0.50 Hcl, I would then repeat the whole procedure again with 0.75, 1.00 and 1.50 Hcl concentrations, repeating each and every one of them three times to get an accurate average of the volume of Hydrogen gas in syringe. I would then record the results in a table of results, to make it easier for every one to read, compare and see the pattern, that every time the concentration of Hydrochloric acid was increased, the rate of reaction went up with it.
Table of results:
Concentration of Volume of Hydrogen Average amount
Hydrochloric acid gas in cm³ / 30 seconds of Hydrogen gas
(Hcl) 1st 2nd 3rd
0.25 12cm³ 15cm³ 15cm³ 14cm³
0.50 20cm³ 29cm³ 29cm³ 26cm³
0.75 50cm³ 50cm³ 50cm³ 50cm³
1.00 65cm³ 65cm³ 50cm³ 60cm³
1.50 45cm³ 50cm³ 48cm³ 47.6cm³
The experiment done with Hcl concentration 1.50 was done again, as it produced some really odd results. The reason for these odd results was that the tube connecting the cork on conical flask with Ground Glass syringe was not completely tight and was leaking gas. So this particular test was done again.
1.50 63cm³ 65cm³ 67cm³ 65cm³
Conclusion: After completing my tests to find whether concentration has any effect on the rate or speed of a reaction, I have concluded that a reaction is, in fact affected by a concentration, depending on if it is either in a higher or lower concentration. However, how much a reaction gets affected depends upon how concentrated the solution is. In our own experiment, when Magnesium reacted with 0.25 Hcl, it produced on average only 14cm³ of Hydrogen gas, but as we progressed further in to the experiment, I could see that the Hydrogen gas produced by Magnesium increased, when it was subjected to react with higher concentration of Hydrochloric acid, e.g. 0.50 and 0.75. The reason for this was that when the concentration of Hydrochloric acid was increased, there were more particles of Hydrochloric acid, which inevitably bumped into the particle of Magnesium and speeded up the reaction. This is known as COLLISION THEORY. As I increased the concentration of acid further to 1.00, it was clear to me that the amount of Hydrogen gas produce will also increase and so the gas produced this time was on average 60cm³. However, when Magnesium was subjected to react with Hydrochloric acid of 1.50 concentrations, the amount of Hydrogen gas produced was 65cm³. Moreover the rate of reaction was so fast that all of the 4cm of Magnesium was completely used up and disappeared few seconds before the limit of 30 seconds was over. This could well be the reason, why, when Mg reacted with 1.50 of Hcl, the volume of Hydrogen gas produced was only 5cm³ more than that of Mg reacting with 1.00 concentration of Hcl.
Ultimately, based on my scientific knowledge, my results and graphs I have concluded that the concentration does play a big part in the speed of a reaction, which was established so easily by the experiment I conducted involving Magnesium and different concentrations of Hydrochloric acid. Temperature is another factor which can influence the rate of a reaction, by giving the particles more energy to allow them to move around more, so that there chances of bumping into particles of another substance also increase and the rate of reaction speeds up. Ultimately, to speed up a reaction, you either need to increase the particles of one of the elements involved in the reaction or, you need to give them more energy to move around more, so that there chances of a collision with the particles of another element involved in the reaction improve and the rate of reaction increases with it. However, the focus of this experiment was to see whether the concentration affects the rate of a reaction; so increasing the temperature to give particles more energy was not considered as this will completely change the nature of the experiment.
Evaluation: Although this experiment was fairly easy and chances of hazards were quite slim, there are certainly some areas where there is a room for improvement and the accuracy of results can be improved. One area which urgently needs attention is the bent tube, which is connects Ground glass syringe with the conical flask. During my experiment I realised on more than one occasion that this tube was loose when attached to the ground glass syringe and so there is a possibility it could have been leaking Hydrogen gas. Because of the loose tube, I had to keep my hand on this tube and keep it tightly connected to the syringe to stop it leaking gas.
Another way to improve this experiment would be to use a test tube with a tap in it, which can be attached to conical flask; rather than using a cork. The reason why I recommend this, is that when we add Magnesium to Hydrochloric acid, we have to rush to close the conical flask quickly with the cork and bent tube attached to it, but still some of the Hydrogen manages to escape and the end result of the test is not so accurate. By using a test tube with a tap in it, we can measure Hcl and pour it in the test tube, but not open the tap just yet. Then we can put 4cm of Magnesium in the conical flask and after we have put the Magnesium we can open the tap and let go of Hcl, so that all the Hydrogen produced is collected in ground glass syringe and none is lost to the outside atmosphere.
Another area where there is room for improvement is in calculating the rate of reaction. In my experiment I calculated the rate of reaction by measuring the volume of Hydrogen gas produced by different concentrations of Hcl reacting with Mg in 30 seconds. To validate and double check our results we can use another method of calculating rate of reaction by calculating loss of mass in reactants. To use this method we need conical flask, Hcl of different concentrations, Magnesium, electronic balance and a stop watch.
In this experiment, we put 40cm³ of Hcl of whichever concentration we want in conical flask and weigh it altogether. We then weigh 4cm of Magnesium and add its weight into the combined weight of Hcl and Conical flask. We then ready the stop watch and put Magnesium into the Hcl. The crucial difference between this method of calculating rates of reaction and the method we used in the experiment is that this method allows the Hydrogen gas to escape and measures the rate of reaction by comparing loss of mass with the time it took to lose that much mass.
After I add Magnesium to Hydrochloric acid, I will start the stop watch and after 30 seconds, I will record the mass of the mixture, which should be less than before, as some of the Hydrogen gas must have escaped because of the reaction. I will then record the mass of the mixture after 60 and 90 seconds. To find the rate of reaction for that particular concentration of Hcl, I will have to use a formula which is; Loss of mass in reactants
Unit
I will then use exactly the same procedure for other concentrations of Hcl and by using this formula: Loss of mass in reactants / unit
I should be able to find the rate of reaction. I will then put the results in a table of results and compare. If the procedure is done correctly, then the results form this method should not be different from the results of the method I used in my experiment.
I we were to do the whole experiment again, to find out if concentration has any effect on the rate of reaction, I would certainly implement all of these corrections suggested in my Evaluation, so that I get results which are highly accurate.