This coursework is aimed to find out the rate of reaction between hydrochloric acid and magnesium in different temperature. The product of this chemical reaction is magnesium chloride and hydrogen.
Safety:We should wear lap coat and wear goggles when doing this experiment, because acid is corrosive and irritant, especially when you boil it, it is very easy to spit into your eyes and it is harmful, so we must keep wearing on the goggles all the time. Lap coat is also needed to protect our skin from contacting the acid. If our skin contact with the acid, we should immediately wash it under the tab water. Magnesium is highly flammable, so we should keep it away from the fire. We should also be careful when using the syringe and other glassware.Preliminary work:In this preliminary work, the aim is to find out the suitable length of magnesium ribbon, the suitable concentration of acid and the suitable volume of the acid, and the temperature range I plan to investigate. I tried a 3 of magnesium ribbon but it gives out too little gas (35) which is very hard to measure and 7 are too long, due to magnesium’s mass, it is lighter than acid, so it is floating on the acid which means it’s surface area are not all contacting with the acid, which makes the test unfair, so I figure out 5of the magnesium ribbon, (gives out about 55of hydrogen) is the best. At first, I planned to use 50% acid (10 water and 10of acid) but when find out that the hydrogen given out are so fast that which is very hard to measure.
It is also very hard to draw the graph if not enough results are collected, Also because of very little volume, it is very hard to control the temperature, so I decided to use 20of acid and 40of water which is about 33% acid is the best, it is much more easy to control the temperature and the speed of giving out hydrogen are not too fast. I tried to heat up the acid to about 90 degree Celsius but the acid began to evaporate which affect the concentration of the acid, so I will use 5 degree Celsius as a range each time and 60 degree Celsius is the maximum.Method:Firstly I measure out 5 of magnesium and weight it. Then I put 20of hydrochloric acid in to a measuring cylinder, 40of distilled water into another measuring cylinder, then put them both into a conical flask and stir it. Secondly I boil it to about 5 degrees below the temperature because it will keep on rising after taken away from the fire. Then I put in the thermometer to stir it and measure out the starting temperature, after that I put in the magnesium and put on the lid and start counting the time; I record down the volume of hydrogen given out every 15 seconds.
Finally, record down the final temperature of the solution and the final volume of hydrogen given out.Apparatus using:Gauze x1Conical Flask x1Bunk x1Delivery tube x1Gas syringe x1Measuring cylinder x1Thermometer x1Bunsen burner x1Fireproof mat x1Stop clock x1Apparatus are Set-up as shown in the diagram.Word equation of this reaction:Magnesium + Hydrochloric acid ? Magnesium chloride + HydrogenEquation of this reaction:Mg(s) +2HCl(aq)?MgCl2 (aq)+H2 (g)Fair Test:In order to keep this as a fair test I just change the temperature and all others variables remain unchanged and reasons, such as:1) Particle’s size,If the size of the particle is changed, the surface area will difference, which means the contact surface are changed, if you use 5of magnesium ribbon, the reaction speed are different from 5 of magnesium powder, because powder’s surface area are much bigger than the ribbon, and it speeds up the reaction, which vary the result, so it is better to use magnesium ribbon, because it can keep the surface area a constant. (Collision Theory)2) Concentration of hydrochloric acid,If the concentration of the acid is changed, the particles of acid will varies and the collision will increase/decrease, and this will affect the speed of reaction therefore the test will not be fair and the results are not reliable, so the concentration of the acid should keep at a constant. (Collision Theory)3) Volume of hydrochloric acid,I will use excess amount of acid because this experiment is aimed to find out the time needed and volume of hydrogen given out by a certain amount of magnesium, so excess amount of acid is needed to dissolve all the magnesium. If the amount is not enough which means it cannot dissolve all the magnesium and it can’t keep this test fair.Prediction:I predict the reactions between the acid and magnesium will be faster as you increase the temperature, when you heat up the acid, the acid particles are more active and move more faster, so there will be more collisions between the magnesium particles and the acid particles, therefore it will also increase the number of successful collisions which lead to increasing the speed of the reaction.
(Collision Theory) I also predict the hydrogen given out will be much faster when you increase the temperature. When you plot out the graph, I predict it will be like the following:I predict the graph should be straight line if not too many errors occur, because the amount of hydrogen released by a certain amount of magnesium should be the same, so that the time and temperature should be in direct proportion. Also I predict that this is going to be an exothermic reaction because of forming bonds between magnesium and chloride.Obtaining Results:The results collected from the experiments are shown on the table.Weight of Mg/gStarting temperature/?CFinal temperature /?CHydrogen given out/Time/sec0.0491821501530.
049504949380.05050515142Rate of hydrogen gas given out every 15 secs at 18?CTime/secVolume of hydrogen given out/experiment 1experiment 2Average15877.530131413.5451820196024262575293230.590353836.
5105404341.5120454645.5135484747.5150505150.5Rate of hydrogen given out every 15 secs at 25?CTime/secVolume of hydrogen given out/experiment 1experiment 2Average15101110.530192019.
545282928.5603638377543454490485049105495049.5Rate of hydrogen given out every 10 secs at 30?CTime/secVolume of hydrogen given out/experiment 1experiment 2Average109109.52016181730262726.
54033373550424543.56047494870504949.5Rate of hydrogen given out every 10 secs at 35?CTime/secVolume of hydrogen given out/experiment 1experiment 2Average10121111.520242022303331324042404150494647.560504949.5Rate of hydrogen given out every 5 secs at 40?CTime/secVolume of hydrogen given out/experiment 1Experiment 2Average51099.510161515.51522202120282727.
525333031.530383838354345444047494845505150.550515151Rate of hydrogen given out every 5 secs at 45?CTime/secVolume of hydrogen given out/experiment 1Experiment 2Average5108910181416152622242033273025393436.5304640433550484940525151.5Rate of hydrogen given out every 5 secs at 50?CTime/secVolume of hydrogen given out/experiment 1experiment 2Average5911101019232115262927.520323533.
525394240.530454846.535495150Analysis:From the graph above, I decided to use a best-fit line in order to connect all the points together on the graph, and I recognise the beat-fit line is the best. From the above graphs, there is something obvious we could see.Firstly we can see that in first 7 graphs, every line start from the origin and it increase continuously, then the lines began to bend down at the end.
Then the line stops as the magnesium finish. This tells that the speed of reacting is faster than the end of the reaction. And when all the magnesium is used up, the line stopped.Secondly, It is obvious that when the temperature becomes higher, the reaction becomes much faster (shown on the last two graphs), the gradient of 50 degree Celsius increase more rapidly than the 18 degree Celsius. Whcih means the slope of 50 degree Celsius is much more deeper than the 18 degree Celsius one.The deeper the slope, the faster than reaction takes place,it means the 50 degree Celsius’s reaction rate and the speed of reaction are much faster than the 18 degree Celsius one.This means that a higher temperature acid neutralise the magnesium much more faster and the rate of reaction is also faster than the low temperature ones, it means that when the temperature increase, the reaction becomes much more faster, it can be explained by the collision theory.
When the temperature rise, the energy on each of the acid particles increase, as they move faster, there is a bigger chance to hit the magnesium particles, this also increase the percentage of successful collisions, as a result, the reaction becomes much more faster, so it takes less time to take the reaction as the temperature rise.Thirdly, the graphs also tell us that no matter what is the temperature, a certain amount of magnesium give out a certain volume of hydrogen gas. In the experiment I’ve done, I can see that the average weight of the magnesium I used is 0.05g and the average hydrogen given out is 50.21, so I recognise that 1 cm of magnesium ribbon weight about 0.
01 gram and every 1 cm of magnesium ribbon give out about 10of hydrogen.Weight of Mg /gHydrogen given out /0.049500.050510.049490.051500.048500.
050510.05050.21The experiments turn out mostly the same as my prediction, I predict that higher temperature makes the reaction faster, my prediction graph matches mostly to the result, I predict the temperature of the solution will rise after the reaction, and it turns out as I expected, then it also turns up that the rate of reaction will be faster as I increase the temperature which also match with my predictions. But there is also some difference, I predict the line will be a straight line but the result line turned out to have a little curve at the end, which means the rise of temperature is not directly proportion to the time of reaction, and it is differ from my prediction, I also predict that the volume of hydrogen gas will be the same, but the result tell me it isn’t. I think this is because of errors, but anyway it still difference from my prediction.Evaluation:On overall, I think I have done the experiment quite well, I could draw some graphs by the result, and that turns out to be an acceptable results, so I think the overall results is acceptable, but there is still lots of ways that I can improve.Firstly, I done all the experiment by myself, which is a pretty hard job, I have to cover the bung onto the flask, start the stop clock, and put in the magnesium the same time , which is quite impossible to do all this three things at the same time.
So it causes some errors, like the inaccurate of hydrogen measurement, as there is some gas loss between the time I put the magnesium in and cover the bung, and also that I didn’t start the timer exactly the time the magnesium reacts with the acid. I think this could be improved if a group of people works together.Secondly, the weight of the magnesium is not being the same every time, which may vary the volume of hydrogen given out. This could hardly be improving, if we add in extra magnesium to make the weight the same, the contact surface will change which make it even worse.
Thirdly, the concentration may not be a constant as the dilute acid’s concentration may not be the same when they are given to me .Human eyes are not reliable for accurate measurement, so the ratio of water and acid may varies when I use a measuring cylinder to measure the acid and the water. The acid which is heated may evaporate a bit. These are very hard to improve as human eyes cannot look at things very accurately, also I can just keep the temperature as low as possible to avoid the acid evaporate.Fourthly, the magnesium is always floating on the acid , which varies the contact surface area of the acid with the magnesium and it makes the result inaccurate.
Lastly, the reading of the thermometer and the volume of gas syringe may not be very accurate, as I have said , human eyes are not very reliable.Although there is lots of area, I still did all my best to keep the result more reliable and there are several things I can improve. I should measure the volume of hydrogen gas given out in a smaller range which can make the graphs more reliable and accurate, and I should do the experiment several more times and calculate out the average which can make my results more reliable and I should work in group of about three, which can keep the varieties as less as possible and make the experiment more accurate.