GCSE OCR Gateway C4:1d-f Displacement reactions of metals: The Reactivity Series of Metals (2)

GCSE OCR Gateway C4:1d-f Displacement reactions of metals: The Reactivity Series of Metals(2)

C4.1d To be able to predict possible reactions and probable reactivity of elements from their positions in the Periodic Table.

C4.1e To be able to explain how the reactivity of metals with water or dilute acids is related to the tendency of the metal to form its positive ion including reaction of metals with water, dilute hydrochloric acid and the displacement reactions involving metals and metal salts.

C4.1f To be able to deduce an order of reactivity of metals based on experimental results.

Displacement reactions of metals.

Displacement reactions of metals are redox reactions.

What happens in a displacement reaction is that a more reactive metal reduces a less reactive metal ion to the metal.

So magnesium reduces copper ions to copper in aqueous solution.

A classic experiment that demonstrates the reactivity series can be set up as follows:

In four boiling tubes, place equal volumes (say 25ml) of 0.5M copper sulfate solution.

Add the same number of moles of four different metal powders to the tubes.  I use magnesium, zinc, iron and copper powders.

Using the same number of moles means you are adding the same number of atoms of each metal to the copper sulfate solution.

Add a 0-100℃ thermometer to each tube and measure, after stirring, the maximum temperature reached.

Each reaction is exothermic and the higher the increase in temperature the more reactive the metal.

Mg > Zn > Fe > Cu

The experiment can be done in a class/lab and each groups results can be collected and averaged. 

This final step has the advantage of judging data: spotting and eliminating outliers.

Displacement reactions are redox reactions and we can unpack the reaction like this:

The reduction and oxidation half equations include the number of electrons transferred between the copper atom and silver ions.

You should be able to construct the other redox equations for the displacement reactions in the table above.

So finally to repeat the principle involved here:

The more reactive metal reduces the ions of the less reactive metal.

Take any pair of metal and metal ion and if there is a reaction ( you observe may be fizzing or one metal dissolving or plating the other) then the metal without ions is more reactive than the metal with ions.

You should also observe the temperature of the metal/metal ion mixture increase.