Metal Reactivity Coursework

Predictions:

From the secondary source "Chemistry Counts" by Graham Hill I can predict that the reactivity series will look like this:

Magnesium

Aluminium

Zinc

Iron

Copper

The Series is most reactive at the top and becomes less reactive as you move down.

Calcium is not included above. But from preliminary work done I have learnt that calcium is very reactive and that it is very hard to test the temperature given off in this reaction by using the methord of testing which I am planing to use in this experiment. Each time I tryed the experiment with calcium the reaction was that vicarious that the solution bubbled over the top. Therefore losing heat in the process making this an unfair test so I have decided that calcium is more reactive than any of the other metals I am using in this test. Also the valence shell is further away from the nucleus in Calcium than in Magnesium it is easier for Calcium to lose its electrons therefore it is more reactive than Magnesium. Supporting my case that calcium is the most reactive metal that I am testing. This valence shell theory applies to all the other metals in the series.

It can be clearly seen that there is a connection between the metallic radii of the metal (i.e. how far the valence shell is from the nucleus) and the reactivity of the metal. If we put the metallic radii of the 6 metals in order next to my prediction of reactivity, they are the same:

Metal

Metallic Radii

Calcium

0.197

Magnesium

0.160

Aluminium

0.143

Zinc

0.133

Iron

0.126

Copper

0.128

This suggests that there is a distinct connection between the metallic radii of the metal and its place in a reactivity series. My final prediction, therefore, starting with the most reactive is:

Calcium

Magnesium

Aluminium

Zinc

Iron

Copper

Apparatus:

250 Ml beaker

Expanded polystyrene cup

100 Ml measuring cylinder

paper towel

electronic scales accurate to at least two decimal places.

hydrochloric acid at a concentration of 2mol/dm3

mercury thermometer graduated to 1°c

electronic timer

plastic lid

Two lots of 0.1 mol of each metal:

Table of amount of each metal needed:

Metal

Mass of 0.1 mol (in g)

Calcium

4

Magnesium

2.4

Aluminium

2.7

Zinc

6.54

Iron

5.6

Copper

6.35

A degree of accuracy is important, which is why everything used in this experiment should be constant except for the metal involved. Testing each metal twice makes sure an accurate reading is taken, without fear of using a 'bad' result.

Diagram of apparatus:

Key factors:

Room temperature.

Room pressure.

Key Variables:

Concentration of acid- must be constant.

Amount of acid- a constant volume (0.1 moles).( The reason for only 0.1 mol is that you need two moles of HCl to react with one mole of a metal. So as I want to have an excess of metal I am only going to use half of the acid needed to react with the metal)

Mass of metal- 0.1 mol

Time readings are taken every 30 seconds for nine and a half minutes

Having the above as constants adds to the accuracy of the experiments.

Amount of acid needed.

I want to use double the amount of metal than acid needed to react with the metal. The chemical equations are the following:

(I am using M as the symbol for metal, and assuming M forms M²+ ions we can write a general equation as)

M + 2HCL = MCl2 + H2

So therefore I need 0.1 mol of HCl

2 mols per 1000 Cm3

50 cm3 * 2 mols = 10

000cm3 100

=0.1mols of HCl

so therefor I need 50cm3 of HCl for these experiments

Method:

Place the cup into the beaker, this is for two reasons 1. To keep the cup stable so it does not fall over and spill out and cause an accident. 2. To add extra insulation to the cup to mimalize heat loss as heat is what we are measuring in the experiment. Then measure out 50 cm3 of HCl and take an initial temperature reading. Weigh out 0.1 mol of the metal then add that to the acid and start the timer. You then take the temperature every 30 seconds for 91/2 minutes. Repeat this two times with each of the five metals( excluding Calcium). Plot each metals results on a separate graph. Having done this, extrapolate each of the metals three curves and thereby obtain the maximum temperature rises for each test substance. Take the average of each of these sets of results and compare them, perhaps in conjunction with metallic radii.

Results:

Magnesium:

Copper:

Aluminium:

Zinc:

Iron:

Conclusion:

By looking at how the data has fallen on the graph I am able to place the metals in to there order of reactivity which goes like this:

Calcium

Magnesium

Aluminium

Zinc

Iron

Copper

The Series is most reactive at the top and becomes less reactive as you move down. The Series is how I predicted it.

If I compare this results to their metallic radii (how far the valence shell is from the nucleus) I have noticed that the larger the metallic radii the more reactive it will be. This is because the future away the valence shell is from the nucleus there is less force keeping it there so it is easier for that atom to give away that last electron.

Evaluation:

I believe that this experiment went well giving out the results that are correct I also believe that the experiment that I had conducted also when as fairly as I could make it in the classroom labroties. If I was to do the experiment again and I wanted as accreat results as i possibly could and the experiment to be as fair as it could, I would have to use an more accreat way of measuring the temperature rise such as an sensor to a computer, as when I did it I only had an thermometer in if I wanted it to go down to the decimal placing had to be gess work as it was in this experiment. I would also change the way I insulated the experiment, not that mine was not effective but there are even better ways of insulating it. I would also use metals that had not been exposed to the air as the air reacts with them and on some metals such as iron it forms an less reactive coat on the metals. That is what I believe happen to all of my meals apart from Magnesium, as there paths should have followed that of Magnesium in the sense that it goes up then down, but in my experiment they did not, this I believe is because the had all ready reacted with the air forming an coat on the metals and that is why I took longer for them to react as the acid had to react with these coat first.

Rhys Beddoe

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