Acid (Hcl) and Magnesium (Mg) Essay
Acid (Hcl) and Magnesium (Mg)
What it also means is that more collisions are successful as the particles impact with a greater force and more bonds are broken. To show how I calculated the rate of reaction graph I have included a table. Temp (0C) Total Volume (cm3) Time taken (seconds) Rate (volume/time) (cm3/s) (to 2 dp) EXPLAINING WHAT HAPPENED Please note that the number of the finding corresponds with the number of my list of findings, on the last page. Finding 1). The rate of reaction increased because the atoms are gaining more energy.
The atoms gain kinetic energy from the heat which is produced. So if you increased the temperature you therefore, are increasing the heat energy supplied to the atoms. This in turn increases the kinetic energy and the atoms move faster. If the atoms are moving faster they collide more often with each other and therefore, increase the rate at which they react. Another factor is activation energy. This is the energy needed at which two atoms can collide with each other with sufficient force to break bonds. The higher the temperature the more energy is supplied to each atom.
Therefore, the greater chance that when the two atoms collide they will have enough energy to break the bonds and create a reaction Finding 2). As I mentioned earlier this went against what I had said in my prediction. Because I had said that the final amount of Hydrogen formed should not be over 70. 8cm3 and this should be the final amount of gas formed for each experiment. However, while doing the experiment itself I found the answer to this problem. If you look at the diagram of the apparatus you will see that the pipe leading to the gas syringe from the chronicle flask is ascending.
We also know that hot air rises. Therefore, the hotter the hydrochloric acid, the hotter the air in the flask and the hotter the gas the leaves the reaction will be. So the air will rise more and the gas formed will rise more. So if the temperature was higher the more gas actually rises and therefore, the gas syringe indicates more. Also at a higher temperature the normal air rises more, and so that may have collected in the gas syringe. Another reason may be that as the atoms were moving slower as the temperature decreased, therefore, many atoms may have just never come in contact.
Or maybe it is because of the fact that the reaction is exothermic and as the experiment goes on the solution losses temperature and therefore, here is not sufficient activation energy for the atoms to react. In the higher temperatures the temperature would have decreased faster because the reaction is giving out energy faster, but by the time the temperature has decreased to a level where there is not enough energy a lot more gas would have been formed. The reason that the final amount of gas formed in the reaction for 600C, 500C and 400C is higher than 70.
8cm3, can be explained by the evaporation of water. Because the acid is diluted it contains a significant volume of water mixed with it. Therefore, at higher temperatures this water may have evaporated, causing two unwanted occurrences. Firstly, this means that the water which evaporated made it seem as though more H2 was being formed, and so steam was also being collected in the syringe, and that the experiment was not fair. And because the water had evaporated it would have caused an increase in concentration, automatically adjusting one of my variables which were meant to stay the same. Finding 3).
This could be due to a technical problem, the gas syringe may not have worked properly, or the tube may have been blocked. If my memory serves me correctly I distinctly remember doing both the first and second attempts of the 200C investigation on the same day, and not doing any other temperatures. This could easily mean that part of the apparatus was faulty. Finding 4). The fact that neither temperatures match up is confusing but not unexplainable. The important number to keep in mind with the experiment is the final volume of gas formed, and those normally stay to within 3cm3 of each other.
What happens during the reaction is a different matter. It could be that the hydrochloric acid was not measured accurately enough, or the temperature of the solution may have been a degree off. Apart from that the results do seem to be accurate enough. That means that I can have one conclusion on the investigating the effects of temperature on the rate of reaction between hydrochloric acid and magnesium: An increase in the temperature = an increase in the rate of reaction. However, this is too simple. And below is another more reasoned conclusion. An increase in the temperature = An increase in the level of energy supplied to atoms =.
An increase in the kinetic energy in the particles = Particles moving faster and colliding more often, and with a greater force = More successful collisions = more collisions and more breaking and forming of bonds = A greater rate of reaction. EVALUATION ERRORS AND THE WAYS TO FIX THEM Looking at my result I can say that they are sufficient enough to draw up the conclusion which I have made. And that they do not seem to bring out any extremely anomalous results However, one point which must be touched upon is the difference between the readings taken on the first and second attempts of a temperature.
There may be many different factors affecting the reliability of these readings. One may be that when the temperature of the water bath is set it is set around 5 degrees warmer than the actual temperature. This is so that the Hydrochloric acid heats up quicker and so that it stays constant as the water become cooler. In some cases the water may have become hotter than intended and the reaction may have taken faster as the solution may have heated up during the actual experiment. I also noticed that the volume of the acid decreases as it is heated.
This maybe due to the fact that hydrogen from the liquid evaporates from the solution. This may have thrown off the accuracy of the investigation. However, the chance that hydrogen evaporated is not as likely, as water. Because the Hydrochloric acid has been diluted there is a significant amount of water, making the HCl less concentrated. However, at the higher temperatures the water might have evaporated, and caused the concentration of the acid to increase. To solve this problem I two thing must be done. The hydrochloric acid must be accurately measured at the correct temperature, so to stop any extra energy being given off.
To stop gas from leaving the hydrochloric acid the solution must be put in a container exactly the same volume as the acid. This means that there is no where for the gas to leave the solution, and drift about. Also to stop gas from leaving the hydrochloric acid there should be a slide to stop gas from going into the gas syringe. This is the same for the evaporation of the water. We can see from the graph, other problems. One of them is the fact that during the investigation for 200C we see a set of anomalous results which do not fit the line of best fit.
We need to know why this happens, and improve our reliability. And bellow in the, next heading, I have tried to show ways of improving reliability INCREASING RELIABILITY As we can see from the graphs there are a few anomalous results, and some of the 2nd tries do not match the first, and to fix these we need to know why these may be happening, and to then, give ways to improve the reliability had these experiments been done again. 1) It is very difficult to get the water bath to the exact temperature, so this can vary and effect the movement of particles in the reaction.
To improve this we can get more accurate water baths, and spend more time exacting their temperatures. Also because the AC was on the water bath may have kept cooling down after it reached the desired temperature. 2) During one experiment the syringe began sticking, and the pressure of the hydrogen was not enough to move the syringe. We fixed that by cleaning the syringe thoroughly. However, there is still a possibility that the syringe was faulty and gave inaccurate readings. To improve the syringe’s reliability we must only ensure that it stays clean, and slides freely.
3) The flask was not fool proof, and there may have easily been a leak in the tube, or where the tube meets the flask or the syringe. To increase the reliability of this the tubing should be sealed tight, and should be enforced with air proof seals. 4) The gas syringe may not have been perpendicular to the clamp stand. This means that it may have been sloping either downwards or upwards. If the gas were to push the tube only a slightly, the force of gravity may have pulled it down even further. 5) When the experiment was started the bung had to be taken off to put in a piece of magnesium.
The bung had to then be placed back on very fast, as to let no gas escape. However, gas particles move faster than the human hand, and may have escaped before the bung was placed back on. This may explain why the rate of reactions, for the first few seconds of the 500C and 200C experiments were slower than the first few seconds of the 40oC and 10oC experiments respectively. 6) Another reliability flaw, that wasn’t actually a problem but, as I said, a flaw in reliability. It was that not all the hydrogen formed may have been collected, or that more was collected in the 60oC experiment than in the 109C.
Firstly, in the conical flask there is an empty space around 50cm3 which is not taken up by the solution. This means that there is a possibility that 50cm3 of gas may have not been collected. This would be ok had this happened to all the experiments. However, this would not happen because on when you have a higher temperature the gas is hotter. And we know that hot air rises, so in the higher temperature experiments the more of the hydrogen which was left in the conical flask may have risen and gone into the syringe.
However, at 100C the hydrogen may have not risen at all, and so nearly 50cm3 of gas may have not been recorded. 7) When it come to reliability one of the major concerns is measurement. In the experiment we used a measuring cylinder to measure out 50cm3. A burette would have been a better choice of apparatus to choose. This is because a burette’s base has a smaller surface area than a measuring cylinder, and therefore, is more sensitive to small changes in the volume. When I measured out the magnesium I used a ruler. T
University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 12 October 2017
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