Resistance Safety – must always wear safety glasses and we should be very careful not to drop any acid.
Fair test- we must make sure that we use the same size, amount and roughly the same mass of chips, this is because we want to keep the chips roughly the same all the way through the experiment so that it will be a fair test and the results we be in relation to each other, otherwise the results will be completely different to what we will expect and it will ruin the experiment. We must also take our readings at the same intervals throughout the experiment i.e. I will take a reading every fifteen seconds for all of my experiments. I predict that the more concentrated the acid the quicker the reaction will take place, because the more concentrated the acid is then it will make the chips react faster and more hydrogen will be given off in a quicker time.The smaller the stones are, the even quicker the reaction will happen, this is because the acid has a smaller surface area to act upon. Equipment- We will need a boiling tube, calcium carbonate chips, hydrochloric acid, water, a stop watch, a gas syringe and a bung on the top of the boiling tube with a delivery tube connected to the gas syringe. I will also need a stand and a clamp to hold on to the syringe.
Method When doing my experiments I will use the same procedure throughout. Once I have set up the apparatus I will measure out 5cm3 of acid in a measuring tube and then pour it into a boiling tube. Then I will be ready with the stop watch and then quickly drop in the chips into the acid, push on the bung and and start the stop watch.This must all be done in a very short space of time. From there, I must take the reading from the volume in the gas syringe every fifteen seconds very accurately until it reading is not changing very much. I must record the results in a table and then write it up neat later.
The factors which may affect how well the experiment works are how quickly the chips are put in and then the bungplaced on and the stop watch pressed. Although this is a factor it is not really a major factor that will affect the end results, and as long as the time it all takes is kept constant throughout then it should not matter too much.Other factors are what kind of water to use for dilution, I could either use water from the tap which is not very pure or it may be too hot or too cold, or I could use distilled water. Tap water may have some things in it which may affect the results.
The temperature also could affect the experiment because if heat is applied then the particles would move around more and affect the results , and then more gas would be made. I think I will need one result for each concentration and later if I need to repeat any experiments I can do. To get the best results I need to use the equipment in the best possible way.Some ways of doing this would be to twist the gas syringe back and forth so as to not get the syringe stuck, which could affect our results. Another thing would be to sieve the chips so to get the best marbles we can.
An important point is that I must get the right amount of acid and the best size and amount of marbles, because if for 4mol if I used about 4 chips then too much gas will be produced and the syringe will go over the 100 mm3 area in the syringe in a very quick time, and so we will not be able to take correct readings. So to over come this problem we will test to see how many chips and at what size will be the best to use. This is where my trialexperiments, that I did before I started, came in handy because it allowed me to know what amount and size of chips to use. After doing my trial experiments I worked out that 1 medium sized chip around 0.63g would be best to use.But I must remember that if I use 1 chip then I must use 1 chip roughly the same size all the way through on all the different concentrations.
We also did an experiment before to give us an idea as to what to do. It was the reaction between Magnesium and hydrochloric acid. This was a very good thing to do because it showed us how to use the equipment and an idea as to what was to come. I have used a few books to help me with my project, I have used my note book and my GCSE Chemistry Gallagher and Ingram text book where I got a good amount of information. Evaluating Evidence I think that the experiment went very well.
This is because I got all the results that I wanted and they look very good.The results were very accurate and so I am able to make a good conclusion. From looking at my results I can see that there were no poor results which was a good thing and it proves that everything went very well. Even though the experiments went very well I decided to repeat one concentration of acid twice just to see if I could repeat the experiment and get roughly the same results, which is what I did do, and these to went very well.
There was no real source of error in the apparatus along as it all was working well and the way it should of been. The only possibility was if the temperature of the acid had changed from when we did the first reading to the finish i.e from when we did the first experiment, the acid hopefully would have been the same temperature.
From looking at my results and graph I am able to conclude that the more concentrated the acid the quicker the reaction happened and the more gas was produced. As we look at the graph we can clearly see that in all five results at the beginning the reaction happened more quickly than at the end where we can see that it started to tail off.Before I did the experiments I made some predictions they were that the more concentrated the acid was the quicker the reaction would happen and more hydrogen would be produced. This was completely correct because what I thought would happen did. At this point we are able to answer our main hypothesis which was how does changing the concentration of acid affect the rate of reaction between hydrochloric acid and calcium carbonate. The answer to this would be that changing the concentration of the acid will either make it go slower or quicker and more or less gas would be produced depending on whether the concentrations were more or less.