The equation for an exothermic reaction is
Mg + 2HCl MgCl2 + H2
The products made in the reaction between the metal and the acid is Metal Chloride + Hydrogen. The equation is as follows:
Metal + Hydrochloric Acid Hydrogen + Metal Chloride
This is what will be made when the product has reacted.
Variables
Key factors to vary are:
- Strength of the acid
- The amount of each metal
- Temperature of the acid
- Whether to add energy e.g. stirring the solution.
Equipment
- Magnesium
- Copper
- Iron
- Zinc
- Calcium
- 2m of hydrochloric acid
- Stopwatch
- Thermometer
- 5 Beakers
Fair Test
- We must react the same number of atoms of each of the metals with hydrochloric acid. I will use 1/100 of a mole of each metal.
- Use the same amount of acid to react with all the metals I will use 50cm of acid.
Plan
- I will take 5 beakers and fill with 1.5 molars of hydrochloric acid.
- Now weigh the metals and divide their atomic mass by 100. This is to make sure that we are reacting the same amount of atoms. I will use:
- 0.40g of calcium
- 0.24g of magnesium
- 0.56g of iron
- 0.65g of zinc
- 0.64g of copper.
Now with each of the metals I will be able to react the same amount of atoms.
- Take 5 thermometers and put them in the beakers.
- Now place each of the metals in the acid and time with the stopwatch.
- Take the five readings every 15 seconds for 3 minutes.
- After you have done this repeat the experiment and average your results.
- Now I will collect results from other groups to make the results accurate.
Diagram
Results
Our results were repeated
Here is a set of results using the temperature probe. This gave us more accurate results.
Due to the time limit on using the temperature probe only a few of the metals were tested. The selected metals were chosen because of their reactivity in the previous experiment using a normal laboratory thermometer.
Analysis
As you can see from the graphs I have drawn that calcium gave out the most heat therefore was the most reactive. Calcium was also the fastest to react, which was due to the particles colliding due to the energy they received resulting in more heat and the quickest reaction. Copper was the slowest to react and give out the least heat. It reacted the slowest because its particles had little energy to collide with resulting in the slowest reaction; therefore less heat was given out. Copper is the least reactive as it is below hydrogen and it’s less reactive than hydrogen so the displacement reaction cannot take place.
The graph clearly shows that calcium was the most reactive and that copper was the least. The stepper gradient for calcium shows that it had a faster reaction and more heat was given out. The graph for copper shows that clearly less heat was given off and it took longer for the copper to react with hydrochloric acid. As you can see the other metals followed the same pattern, they took longer to react and the graph shows this by the gradients of the metals. The steeper the gradient the faster the metal reacted and more heat was given off.
The results from the temperature probe clearly show a more accurate temperature reading than a normal thermometer. They give a reading to point nought of a degree. This shows again that calcium was the most reactive and cooper was the least reactive. They are accurate results and they show more accuracy than a normal thermometer. The results were repeated to give accurate results to show that the experiment was carried correctly and no mistake were made i.e. human error; the room temperature was too hot, incorrect equipment etc.
I predicted that all of the metals except copper would react due to the fact all the other metals would displace hydrogen. I found that this was correct that copper did not displace hydrogen and all the other metals did because of their positions in the reactivity series. This is because a more reactive element is displacing a less reactive element from its compound.
Copper is one of the metals found at the bottom of the reactivity series; these metals do not give up electrons easily. They have a much stronger hold on their electrons than hydrogen atoms, which means that hydrogen will form its ions more easily than copper. This statement reflects the order of reactivity I have found and the order of reactivity that I predicted. I stated that calcium would be the most reactive due to its position in the periodic table and that copper would not react due to its position in the periodic table. I’ve found that the higher the metal in the reactivity series, the more easily it forms its ions, so the more reactive it is.
From looking at my results and the results from my secondary source these prove that magnesium is a very reactive metal, this is because magnesium in the secondary source displaced the most metals and from my results magnesium displaced hydrogen the quickest. Although calcium was not tested in my secondary source from my experiment it was the most reactive metal and displaced hydrogen in the quickest time. If I look at the results of copper from my secondary source I can see that it displaced only one of the solutions. From my results I can see that this is true, as copper didn’t displace hydrogen due to its position in the reactivity series. If I look at the results for zinc and iron from my secondary source it is clear to see that both metals displaced the same number of solutions. From looking at my results I found zinc was more reactive than iron but only by a few seconds. The results from my secondary source provide further evidence for the order of metals in the reactivity series. They show that metals become less reactive down the reactivity series.
With the temperature probe I found it gave a clearer view to what was happening with the metals. Using the temperature probe it gave accurate readings of the results rather than a normal laboratory thermometer. It was clear to see from using the temperature probe that again as I predicted that calcium was the most reactive metal as it took the shortest time to displace hydrogen whereas copper the hydrogen ions were able to form more easily and this took the longest period of time with hardly any change in temperature.
The rate of the reaction is indicated by the rate at which the bubbles of hydrogen are given off.
When the metal and the acid reacted together they formed a chloride salt and hydrogen gas was given off. The equations for the metals are:
Mg + 2HCl MgCl2 +H2
Fe + 2HCl FeCl2 +H2
Zn + 2HCl ZnCl2 + H2
Ca +2HCl CaCl2 +H2
Cu + 2HCl CuCl2 +H2
As you can see all the metals made salt chlorides.
From the reactivity series calcium is above all the other metals so it will be more reactive. Copper is below the other metals so it will be less reactive. The other metals are listed in the reactivity series below calcium and above copper. This is the order of reactivity:
Calcium
Magnesium
Zinc
Iron
Copper.
The reactivity series is a very useful summary of the reactions of metals. It shows the relative relativities of metals. Metals at the top of the reactivity series are the metals, which want to lose electrons and form ions. Atoms of these metals are reactive, but their ions are stable. Metals at the bottom of the reactivity are the opposite of those metals at the top. Ions of these metals want to gain electrons and form atoms so these metals are less reactive. (From chemistry counts by Graham Hill)
Evaluation
From the investigation I obtained good results and I found the experiment very enjoyable. The experiment was carried out safely and the plan was followed step by step to make sure that there were no errors made. I obtained two sets of results and used a temperature probe for another set of results to give and accurate reading of the temperature. There were a few anomalous results but the results were accurate enough. The results were reliable and proved that my prediction was correct and the experiment was carried out correctly.
The results were reliable but a few errors did occur i.e. anomalous results. This could be due to human error or to the fact the equipment wasn’t as safe and fair enough to be used in the experiment but overall the results were reliable. These problems can be overcome by using more accurate equipment to measure the temperature apart from using a temperature probe. When using the temperature probe not all of the metals were tested again, due to the amount of time I was given to use the probe. The metals that were tested calcium; iron and zinc will show a clear difference in results from using the probe, as temperatures were more accurate than a normal laboratory thermometer.
The conclusions I have made are true for the metals I investigated and other metals would have to be investigated further to see that this is true. Different metals could be used and other liquids could be used i.e. sulphuric acid, nitric acid and water. Investigations could be carried out to show the metals react in air, and water and if these situations will affect the order of reactivity of the metals. Will the results be the same for metals reacted in water as metals reacted in air. Will there be other metals tested to see if there are any metals more reactive than calcium and metals less reactive than copper.
Accurate measuring equipment would have to be used to give accurate, clear results are obtained. The good results would present a clear idea of the reactivity of these metals. Further experiments could be carried, using different equipment to see if my conclusions are true about the reactivity of metals.
