In the preliminary experiment, I will use the smallest amount of Magnesium that can be used, which is 0.024g, and the largest amount of Magnesium that can be used which is 0.24g. I will use these two amounts just to see whether I am doing the experiment accurately and correctly and to see whether my results are following the pattern.
Therefore, to do the preliminary experiment I will weigh the amount of Magnesium I am going to use. I will do this as accurately as possible by making sure that I when I weigh the magnesium it is the exact amount that I want and not 0.01g out. In order to do this as well as possible I am going to have to be very careful and patient. I will then put the Magnesium in a mini beaker, which I will place in a conical flask. This will have 20ml of Sulphuric Acid in it and in placing the beaker into it I will have to make sure that the Magnesium doesn’t touch the Sulphuric Acid as if it does the reaction will occur. After this I will shut the beaker with a rubber bung that has a delivery tube in it and I will place the other side of the tube at the base of a 250ml measuring cylinder, held by a clamp, which will be filled with water and suspended in an ice cream tub of water. When I finish preparing the apparatus I will shake the conical flask to make the little beaker with the magnesium in it fall to cause the reaction. I will carry on shaking the conical flask until the reaction is over and all the gas is collected, and I will read how much gas has been produced in the measuring cylinder. I will do this experiment twice, once with 0.24g of Magnesium and then with 0.024g of Magnesium.
The results that I got were as follows:
Mg + H2SO4 MgSO4 + H2
These results are very close to the results that I am supposed to get which are:
Mg + H2SO4 MgSO4 + H2
Therefore, I am not going to change anything drastic when I do the main experiment. The only things that I am going to do is measure the weight of the Magnesium more accurately than I did by filing the end of the magnesium with san paper so that I can take off the 0.01g that I sometimes left on the Magnesium because I couldn’t get the Magnesium any smaller. Measure the amount of Sulphuric Acid more accurately by pouring it into the mini measuring cylinder on a flat surface before placing it into the conical flask and reading off the amount of gas produce more accurately. I will also try and make sure that when I place the cling film on the top of the measuring cylinder that there are no air bubbles at the top as I found that when there are it makes the final amount of gas larger and inaccurate. Doing this should give me more precise and reliable results.
In the experiment, I will have to maintain, change and observe certain variables. This will be done as follows:
In my main experiment, the apparatus I am going to use:
A 250ml measuring cylinder, a conical flask, 0.024 or 0.24 of Magnesium, 20ml of Sulphuric Acid, rubber delivery tube, ice cream tub filled with water, mini beaker, a boss and clamp, cling film, sandpaper
I am going to set up the apparatus like this:
I am going to use a 250ml measuring cylinder because it means that there is just enough space for me to do my largest amount of magnesium so that I can read it off the measuring cylinder. This is because my largest amount of magnesium is 0.24g, which should produce 240cm3 of hydrogen gas; this amount of gas will fit fine in the measuring cylinder. The measuring cylinder is also big enough to fit my smallest amount of gas in which is 40cm3. The measurements on the side of the measuring cylinder are also quite big and easy to read. As you can see, I am also using cling film in the experiment. This is to cover the top of the measuring cylinder as I turn it upside down to submerge it in the water of the ice cream tub and attach it to the clamp. I used cling film instead of other substances that I could have used because it is light which means that it just sits on top of the surface of the water and does not sink into it. It’s see-through so it is possible to see if any water bubbles have formed when it is placed on the top. It is also easy for the water t run off which means that it can be used again in the experiment instead of using a new piece every time, which can be very expensive. As well as this, I am using sandpaper in the experiment. This is to sand down the ends of the Magnesium so that it can become the exact mass that it is supposed to. I used sandpaper instead of a nail file because a nail file is made of metal and if some of the metal had come off onto the Magnesium the experiment could have been interfered with and may not have come out correctly. Sandpaper, however, has less of a chance of coming off onto the metal.
The way I am going to carry out the main experiment is I am going to fill the conical flask with 20ml of sulphuric acid and drop a mini beaker, full of my desired amount of magnesium, upright into the conical flask. I must do this making sure that no magnesium falls out of the mini beaker into the acid as otherwise the reaction will start before all of the equipment is set up and I’d have to start again. I will then put the bung fitted with a delivery tube onto the top of the conical flask. Then I will fill a 250ml measuring cylinder filled right to the top with water. I will cover the top with cling film and clamp it upside down so that the bottom of it is just in the ice cream tub, which is also full with water. I will place the ice cream tub on the base of the clamp so that it is stable, take the cling film off of the end of the measuring cylinder and push the delivery tube attached to the bung sealing the conical flask into the end of the measuring cylinder. When I have done this, the apparatus is set up for me to do the experiment. I will shake the conical flask so that the mini beaker in the conical flask tips over and the magnesium falls into the acid. This will start the reaction and the hydrogen gas that is let off will go through the delivery tube and into the measuring cylinder. The gas will collect at the top as shown in the diagram.
In order for my results to be reliable and accurate, I will have to measure everything very precisely using good scales and sandpaper to file the edges of the magnesium to make sure that the amount is exact. I will have to use all of the same equipment, the same acid and the same magnesium. I will have to make sure that when I cover the top of the measuring cylinder with cling film and turn it upside down to attach it to the clamp and lower it into the water that no air bubbles form because this can make the end reading of the volume of hydrogen gas more than it is supposed to. As well as this, I will have to read the reading of the amount of gas off the measuring cylinder more accurately so instead of looking down on cylinder to read the measurement I will look with my eyes level with the measuring cylinder. I will also repeat the experiment to see whether the results that I get are constant and I will also see if the results fit with ‘The Molar Theory’. If they do then my results are correct and therefore reliable.
When I have collected all my results, I will put them in a table and plot them on a graph. From this, I will able to spot any anomalous results that I may collect. In all I will take six results – 0.04, 0.08, 0.12, 0.16, 0.20 and 0.24. This will be a more than adequate amount to make a proper graph.
As I said, I will repeat all of the values to see if my results are reliable and accurate and I may increase the range to see if any other patterns come into action later on down the line.
Obtaining Evidence
I repeated my experiment twice in order to make sure that the results I achieved was constant and that they were as reliable and accurate as I could get them.
My first set of results is as follows:
When I retrieved these results, I took the room pressure and the room temperature. I got these:
I think that these results that I collected I quite accurate and good. They are close to the amounts that I should have got which are:
However, some of the results are closer to the desired amounts than others, which is why I repeated the experiment. This may have happened for many reasons. Maybe because I was not accurate enough with the weighing of the Magnesium or the amount of acid that I used. However, I had to bare all of this in mind for my second attempt at the experiment.
My second set of results is as follows:
When I collected these results, I again recorded the room temperature and the room pressure. I got these:
I think that these results are a lot better than the last results as although they are not exactly at the desired amounts, which are shown above, they are closer and more so than in my first set of results. This could have been because I was a lot more accurate and I measured things more precisely, but it also could have been that the pressure of the room was lower.
Analysis and Conclusion
- Analysis
As I collected two sets of results, I thought it would be a good idea to form a third set of results and graph with the average of the two results. I did this by adding the two results together and dividing the total by two. These are the averages I got:
I also took and average of the room temperature and the room pressure:
I have decided to plot all of the three sets of results on different graphs so that they can be spaced out and to see if the results stick to a straight line showing that the reaction increases constantly.
The gradient of the first line graph is 1125
The gradient of the second line graph is 1062.5
The gradient of the third graph is 1062.5
As you can see all the gradients are the same which shows that all the results were close to each other and that I was only a little bit out each time.
- Conclusions
From the graphs that I have drawn I can see that the second set of results were a lot better than the first. More of the results are crossed by the best-fit line in the second graph than the first. This means that in order to try to get the results the best that they can get I will have to carry on doing what I did after the first experiment. This was just to be more careful with what I was doing and be more precise with certain things, such as the weight of the Magnesium and the amount of Sulphuric acid. This should give me more reliable and accurate results.
Looking at the graph, I can see that as the amount of magnesium increases the amount of Hydrogen also increases but at a steady and constant rate. My results do not exactly show this as some are off the line slightly but they do still follow the pattern to some extent.
From what I can see on the graphs, every five units, on the graph paper, along the x-axis go up the y-axis 50:
I found this out using the best-fit line that I drew. This is the only pattern I can see emerging from my graphs.
From my second graph, I can almost see a numerical relation between the two variables. As the magnesium increases by 0.4g, the amount of Hydrogen gas released increases, almost, by 40cm3. This is not how it exactly goes on my graph due to some slightly inaccurate results; however I know that this is a pattern that is meant to occur in this experiment and I can see it forming slightly in the second graph.
Looking back at my prediction, I can see that my results do agree with my theory that if:
0.50g of metal was used and 100cm³ of gas was produced
When
0.25g of metal was used; 50cm³ of gas would be produced
And when
1.00g of metal was used; 200cm³ of gas would be produced
However my results do not double, they are multiplied by four each 0.4g the magnesium is increased.
My results also almost fit “The Mole Theory”. Although I explained what “The Mole Theory” was above, I will explain it again.
The first part of doing this is to find out how many moles there are in Magnesium, which is the metal I am going to be using. To do this, this equation must be used:
Number of moles = mass ÷ mass of 1 mole
In this case, when I substitute the writing in the equation with the correct numbers I will get:
Number of moles = 24 ÷ 24
Number of moles = 1
The way in which I got this answer is that I know that the Relative Atomic Mass of Magnesium is 24 and that there are no other metals in Magnesium. This means that the formula mass is 24 and therefore the mass of 1 mole is 24g. Therefore, I already know that 1 mole is 24g of Magnesium; however, I did the equation as a check.
After doing this you use the chemical equation for the reaction, in my case it will be the reaction of Magnesium with diluted Sulphuric Acid:
Mg + H2SO4 MgSO4 + H2
As Magnesium is only one mole and weighs 24g, the gas that is produced by the reaction of the Magnesium with the acid should occupy 24l (24000cm3) at room temperature and pressure, knowing this makes it easy to work out how much Hydrogen will be produced when different amounts of Magnesium is used because as:
24g of Magnesium will make 24L of Hydrogen (24000cm³),
0.24g of Magnesium will make 0.24L of Hydrogen (240cm³), and
0.024g will make 0.024L of Hydrogen (24cm³)
This means that for the amount of Magnesium I used, I should have got the following amounts of Hydrogen Gas:
The answers that I got are almost the same as the answers I was meant to get, which are shown above, some of them were unfortunately slightly inaccurate. Therefore, I think that my results do support my predictions but they could have supported my predictions even better if I had achieved results that were slightly more accurate.
Evaluation
I think that the experiment was a very simple and easy experiment to do and that it was possible to achieve excellent, reliable, and accurate results from it. However I believe that in order to do this, the concentration level for this would have to be double than that of any other experiment that we may do because there are so many factors that have to be looked after and cared for at the same time, that are quite hard to do. For example, getting the strip of magnesium to the exact correct mass, and using the exact same amount of acid every time and not getting any air bubbles at the top of the measuring cylinder.
Nevertheless, I think the results that I obtained from this experiment were above par and I think that they were as accurate as I could have got them.
In my first set of results, I have bolded the values I think I slightly odd. I think this, as they are quite a way off what they were supposed to be. The other results were either spot on, in one case, or one or two units out. However the results that I bolded were as much as ten units out, which is quite high. I am not entirely sure why this happened as I managed to achieve quite good results for the rest of them in the first set. All that I think is that I was slightly inaccurate in weighing the mass of the magnesium and measuring the amount of acid and also a few air bubbles may have been made. These are the only reasons I can think of.
Nevertheless, in my second set of results, there were no anomalous results at all; just some of them were one or two units out. This means that I must have looked at what I was doing wrong when the doing the preliminary experiment and when doing the first main experiment and improved or fixed what I was doing wrong. This could have been, as I said earlier, that I was not accurate enough weighing the mass of the magnesium and measuring the amount of acid or that a few air bubbles formed when I placed the cling film on top of the measuring cylinder. Nonetheless, I am not entirely sure what I improved, all I know is that I did improve from the preliminary experiment and the first experiment and my second set of results were a lot more accurate than any others I had taken.
I think that the only reason for my results being slightly inaccurate and therefore slightly unreliable was me. Nothing to do with the method, or the apparatus used or the experiment itself. I think that I was being as accurate as I could have been however, this was not accurate enough and other people could have been and were being a lot more accurate than I was and achieved better results as a consequence. However, after saying this, I am sure if I gave my absolute, full attention to the experiment and repeated it over and over again, trying to improve on things that may need to be slightly improved, I could get the results that I was meant to get. One way in which the experiment itself could have been improved was to use weighing scales that were more accurate. We only used weighing scales that measured the mass up to two decimal places. If we had used the weighing scales that measured the masses to be three decimal places, we would have been able to get the mass of the magnesium a lot more accurate and therefore the results would have come out better and more reliable. The same thing could have been done for the amount of acid used. Instead of us using really small plastic measuring cylinders with the readings along the side really hard to read, we could have used rather large glass ones which would make it easier for us the read the amounts along the side and we would then be able to measure the amount of acid we were using more accurately. These are the only points that I would change to the experiment to make my results better.
I think that my results are just about accurate and reliable enough to draw a “safe” conclusion, as they are quite close to the results that I was meant to get.
My accuracy and reliability did improve when I repeated the experiment because I must have been more careful with things when I repeated it knowing that I might have done them wrong last time I did the experiment. This could have been anything from weighing the mass of magnesium inaccurately to reading the amount off the measuring cylinder wrong.
I think that my results were a lot better than some of the other people’s in the class but some other people achieved a lot better results than I did. I suppose that the results achieved depend on the actual person doing the experiment because if the person is generally careless with things, they will not get good results here, as they would be careless in this as well. However if there was a perfectionist doing the experiment I’m sure that they would get better results than a person who is careless, just due to the way they do things differently.
My results were very close to the results I was meant to get. I only made a few systematic errors and I the case of the first set of results I made three random errors as well.
Overall, I think that my results are more than adequate to support a conclusion, merely because I know the results that I was meant to achieve, they were extremely close to these results, and my results do follow a pattern, which I have already stated.
If I did any further work, I would extend the range of values I used. I would only increase the values and not decrease, as it is impossible to get negative mass. I would probably take another six results to see what happened down the line and to see if the pattern continued. However, this could be quite a hard task, as I would have to find a measuring cylinder bug enough to hold a large amount of gas, larger than 250cm3 and I would have to find a place big enough to do the experiment. This could prove difficult and cost a lot of money.
I would also probably try to collect the gas in a different way but with the same metal and acid. There are many different ways that I could collect the gas. I could collect it using the downward displacement method:
This can be used when the gas is lighter than air, and, as Hydrogen gas is this
experiment will work to collect the gas. Another way I could collect the gas, that may be easier than any of the other experiments stated above, is to use a gas syringe, which is used when the volume of the gas wants to be measured. This works with for any gas:
This would be the only further work I would do.
Sources
In my research and help for this coursework, I used:
GCSE Chemistry (school textbook)
School Notes
GCSE Bitesize Revision Book