Reactivity Series & Corrosion of Metals (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

An investigation was carried out into the reactions of aqueous copper(II) sulphate with magnesium, iron and zinc.

Experiment 1

By using a measuring cylinder, 5 cm³ of aqueous copper(II) sulphate was added to each of three test-tubes. The initial temperature of the solution was measured. Zinc powder was added to the first test-tube, iron powder to the second tube and magnesium powder to the third tube. The mixtures were stirred with the thermometer. All the observations were recorded and the maximum temperature reached measured.

Use the thermometer diagrams to complete the results table.

metal added	initial temperature / oC		maximum temperature / oC		temperature difference / oC	observations
zinc						moderate effervescence, solution paler brown solid
iron						little effervescence, brown solid
magnesium						rapid effervescence, pops with lighted splint, brown solid

Use your results and observations to answer the following questions.

The reactions of magnesium and zinc with aqueous copper(II) sulphate were investigated in more detail.

Experiment 2

By using a measuring cylinder 10 cm³ of aqueous copper(II) sulphate was poured into a polystyrene cup. The initial temperature of the solution was measured.

A 1 g sample of zinc powder was added to the cup and the temperature measured every 10 seconds for 1 minute.

Use the thermometer diagrams to complete the results table.

Experiment 3

Experiment 2 was repeated using magnesium powder instead of zinc.

Use the thermometer diagrams to complete the results table.

time / seconds	temperature / oC
	Experiment 2		Experiment 3
0
10
20
30
40
50
60

Plot the results of both Experiments on the grid below. Draw two smooth line graphs.

Clearly label the graphs.

Use your graph to estimate the temperature of the reaction mixture in Experiment 2 after 5 seconds. Indicate clearly on the graph how you obtained your answer.

Sketch lines on the grid to show the predicted results if Experiment 2 were repeated using:

Why is a polystyrene cup used instead of a glass container?

Suggest one improvement to the method in Experiment 2.

Eight steel rods of the same size were placed in solutions of different pH for one week.

The percentage corrosion of the rods was measured and the results plotted on the grid below.

Draw a best fit straight line through the points. 

Why were the steel rods the same size?

State one other variable which should have been kept constant.

State one conclusion that could be drawn from the results.

Determine the percentage corrosion of a steel rod in a solution of pH 6.5.

An investigation was carried out on the reactions of four different metals. Equal masses of copper, magnesium, iron and zinc were used.

Experiment 1

A 15 cm³ sample of dilute sulfuric acid was added to each of four boiling tubes. The initial temperature of the acid was measured. Zinc was added to the first tube, iron to the second tube, magnesium to the third tube and copper to the fourth tube.

The maximum temperature reached in each tube was measured and any observations were recorded in the table.

How do your observations show that the reaction of magnesium with aqueous copper(II) sulphate is exothermic?

Use your results from Experiments 1 and 2 to put the four metals in order of reactivity.

least reactive ..............................................................................

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most reactive ..............................................................................