Reactivity Series & Corrosion of Metals (Cambridge (CIE) IGCSE Chemistry)

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The position of aluminium in the reactivity series of metals is shown below.

magnesium
aluminium
zinc
copper

Aluminium is extracted by the electrolysis of its molten oxide.

i) Name the main ore of aluminium.

[1]

ii) Why does the molten electrolyte contain cryolite?

[1]

iii) Oxygen is produced at the positive electrode (anode). Name another gas which is given off at this electrode.

[1]

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Aluminium reacts very slowly with aqueous copper(II) sulphate.

2Al(s) + 3CuSO₄(aq)  → Al₂(SO₄)₃(aq) + 3Cu(s)

i) Which of the two metals has the greater tendency to form ions?

[1]

ii) Describe what you would see when this reaction occurs.

[1]

iii) Explain why aluminium reacts so slowly.

[1]

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Complete the following table by writing “reaction” or “no reaction” in the spaces provided.

Give three differences in physical properties between the Group I metal, potassium, and the transition element, iron.

The following metals are in order of reactivity.

potassium
zinc
copper

For those metals which react with water or steam, name the products of the reaction, otherwise write ‘no reaction’.

Potassium:        
Zinc:       
Copper:

Rusting of steel can be prevented by coating the steel with a layer of zinc.

Explain, in terms of electron transfer, why steel does not rust even if the layer of zinc is scratched so that the steel is exposed to air and water.

When a sample of steel is added to dilute hydrochloric acid, an aqueous solution of iron(II) chloride, FeCl₂, is formed.

When a sample of rust is added to dilute hydrochloric acid, an aqueous solution of iron(III) chloride, FeCl₃, is formed.

i) Aqueous sodium hydroxide is added to the solutions of iron(II) chloride and iron(III) chloride.

Complete the table below, showing the observations you would expect to make.

[2]

Solutions of iron(II) chloride and iron(III) chloride were added to solutions of potassium iodide and acidified potassium manganate(VII). The results are shown in the table.

ii) What types of substance cause potassium iodide solution to turn from colourless to brown?

[1]

iii) What types of substance cause acidified potassium manganate(VII) solution to turn from purple to colourless?

[1]

iv) Which ion in iron(III) chloride solution causes potassium iodide solution to turn from colourless to brown?

[1]

v) Which ion in iron(II) chloride solution causes acidified potassium manganate(VII) solution to turn from purple to colourless?

[1]

The reactivity series of metals given below contains both familiar and unfamiliar elements. For most of the unfamiliar elements, which are marked *, their common oxidation states are given.

Choose metal(s) from the above list to answer the following questions.

i) Which two metals would not react with dilute hydrochloric acid?

[2]

ii) Which two unfamiliar metals (*) would react with cold water?

[2]

iii) What is the oxidation state of barium?

[1]

iv) Name an unfamiliar metal (*) whose oxide cannot be reduced by carbon.

[1]

v) Why should you be able to predict that metals such as iron and chromium have more than one oxidation state?

[1]

The reactivity series lists metals in order of reactivity.

To find out which is the more reactive metal, zinc or tin, the following experiment could be carried out.

This experiment could be carried out with other metals and the results are recorded in a table. Then the order of reactivity can be deduced.

i) The order was found to be:
manganese  - most reactive
zinc
tin
silver - least reactive

Complete the table of results from which this order was determined.

[3]

ii) Write the ionic equation for the reaction between tin atoms and silver(I) ions.

[2]

iii) The following is a redox reaction.

Mn + Sn²⁺ Mn²⁺ + Sn

Indicate on the equation the change which is oxidation. Give a reason for your choice.

[2]

iv) Explain why experiments of this type cannot be used to find the position of aluminium in the reactivity series.

[2]

Potassium and calcium are very reactive metals at the top of the series. Because their ions have different charges, K⁺ and Ca²⁺, their compounds behave differently when heated.

 Explain why the ions have different charges.

Steel is an alloy made from impure iron.

Both iron and steel rust. The formula for rust is Fe₂O₃.2H₂O. It is hydrated iron(III) oxide.

i) Name the two substances that must be present for rusting to occur.

[2]

ii) Painting and coating with grease are two methods of preventing iron or steel from rusting. Give two other methods.

[2]

i) Name a reagent that can reduce iron(III) oxide to iron.

[1]

ii) Write a symbol equation for the reduction of iron(III) oxide, Fe₂O₃, to iron.

[2]

i) Calculate the mass of one mole of Fe₂O₃.2H₂O.

[1]

ii) Use your answer to (i) to calculate the percentage of iron in rust.

[2]

Iron from the blast furnace is impure. Two of the impurities are carbon and silicon. These are removed by blowing oxygen through the molten iron and adding calcium oxide.

 i) Explain how the addition of oxygen removes carbon.

[1]

ii) Explain how the addition of oxygen and calcium oxide removes silicon.

[2]

Some reactions of metals W, X, Y and Z are given below.

Arrange these metals in order of reactivity.

Which of these metals could be?

Magnesium ................

[1] 

Copper ................

[1] 

The equation for the reaction of X with cold water is given below.

2X (s) + 2H₂O (l) → XOH (aq) + H₂ (g)

i) Describe the test you would use to show that the gas evolved is hydrogen.

[1]

ii) How could you show that the water contained a compound of the type XOH?

[2]

iii) In which group of the Periodic Table does metal X belong?

[1]

iv) The ore of X is its chloride. Suggest how metal X could be extracted from its chloride.

[2]

Tin is an element in Group IV.

The position of tin in the reactivity series is:

zinc

iron

tin

copper

i) For each of the following, decide if a reaction would occur. If there is a reaction, complete the equation, otherwise write ‘no reaction’.

 Cu + Sn²⁺ → ..........................................

Fe + Sn²⁺ → ..........................................

Sn + Zn²⁺ → ..........................................

[4]

ii) Name the three products formed when tin(II) nitrate is heated.

 [2]

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Aqueous tin(II) sulfate is electrolysed using carbon electrodes. This electrolysis is similar to that of aqueous copper(II) sulfate using carbon electrodes.

i) What is the product at the negative electrode (cathode)?

[1]

ii) Write the equation for the reaction at the positive electrode (anode).

[2]

iii) Name the acid formed in this electrolysis.

[1]

Steel articles can be plated with tin or zinc to prevent rusting.

When the zinc layer is damaged exposing the underlying steel, it does not rust, but when the tin layer is broken the steel rusts. Explain.

This question is about alloys. 

Brass is an alloy which contains zinc.  

i) Name the other metal in brass.  

[1]

 ii) Suggest two reasons why an alloy such as brass is preferred to either of its constituent metals. 

[2]

In an experiment to investigate the rate of rusting of steel, three pieces of steel were used.

One piece of steel was completely coated with copper, one piece completely coated with zinc and the third piece was left uncoated. All three pieces were left exposed to the atmosphere.

i) Explain why the uncoated piece started to rust.

[1]

ii) The coating on both of the other two pieces was scratched, exposing the steel.

The piece of steel coated with zinc still did not rust but the copper-coated piece of steel rusted very rapidly. Explain these observations in terms of the formation of ions and the transfer of electrons.

[4]

Separate: Chemistry and Extended Only

One way of establishing a reactivity series is by displacement reactions.

A series of experiments was carried out using the metals lead, magnesium, zinc and silver.

Each metal was added in turn to aqueous solutions of the metal nitrates.

The order of reactivity was found to be:

magnesium zinc lead silver

most reactive  least reactive

i) Complete the table.

 Y = reacts

N = does not react

[3]

ii) Displacement reactions are redox reactions.

 On the following equation, draw a ring around the reducing agent and an arrow to show the change which is oxidation. 

Zn + Pb²⁺ → Zn²⁺ + Pb

 [2]

 iii) Complete the following ionic equation.

 Zn + 2Ag⁺ → ....... + .......

 [1] 

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Another way of determining the order of reactivity of metals is by measuring the voltage and polarity of simple cells. The polarity of a cell is shown by which metal is the positive electrode and which metal is the negative electrode. An example of a simple cell is shown below.

i) Mark on the above diagram the direction of the electron flow.

[1]

ii) Explain, in terms of electron transfer, why the more reactive metal is always the negative electrode.

[2]

The following table gives the polarity of cells using the metals zinc, lead, copper and manganese.

iii) What information about the order of reactivity of these four metals can be deduced from the table?

[2]

iv) What additional information is needed to establish the order of reactivity of these four metals using cells? 

[1]

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Excess hydrochloric acid was added to powdered zinc. The hydrogen evolved was collected and its volume measured every 20 seconds. The experiments were repeated at the same temperature using the same number of moles of powdered magnesium and aluminium.

Identify metals A, B and C by choosing from zinc, magnesium and aluminium. Give a reason for each choice.

Metal A

Metal B

Metal C

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Using ‘moles’, explain why two of the metals form the same volume of hydrogen but the third metal forms a larger volume.

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The reactions of a metal and the thermal stability of some of its compounds are determined by the position of the metal in the reactivity series.

To find the order of reactivity of the metals, cobalt, magnesium, silver and tin, the following experiments were carried out.

i) Give as far as possible the order of reactivity of these metals.

Write the least reactive first.

[2]

ii) What additional experiment needs to be done to put all four metals in order of reactivity?

[1]

iii) Write an ionic equation for the reaction between tin atoms and silver(I) ions. Indicate on the equation the change which is oxidation.

[3]

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A cell consists of two different metal electrodes in an electrolyte. Three possible cells are shown below.

i) Why is the more reactive metal the negative electrode?

[2]

ii) How can you deduce that zinc is more reactive than tin?

[1]

iii) How could you change the zinc / copper cell to have a voltage greater than 1.1V?

[1]

iv) Complete the labelling of the zinc/tin cell.

[2]

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In the following list of ionic equations, the metals are in order of reactivity.

i) In the space at the top of the series, write an ionic equation that includes a more reactive metal.

[1] 

ii) Define oxidation in terms of electron transfer.

[1] 

iii) Explain why the positive ions are likely to be oxidising agents.

[1] 

iv) Which positive ion(s) can oxidise mercury metal (Hg)?

[1] 

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The following diagram shows a simple cell.

i) Predict how the voltage of the cell would change if the tin electrode was replaced with a silver one.

[1]

ii) Which electrode would go into the solution as positive ions? Give a reason for your choice.

[1]

iii) State how you can predict the direction of the electron flow in cells of this type.

[1]

Separate: Chemistry and Extended Only

Displacement reactions occur between metals and metal ions. Displacement reactions can be used to determine the order of reactivity of metals such as lead (Pb), nickel (Ni), and silver (Ag).

The ionic equation for a displacement reaction is shown.

Ni (s) + Pb²⁺ (aq) Pb (s) + Ni²⁺ (aq)

The ionic half-equations for this reaction are shown.

Ni (s) Ni²⁺ (aq) + 2e^–

Pb²⁺ (aq) + 2e^– Pb (s)

The ionic half-equations show that electrons are donated by nickel atoms and accepted by lead ions.

Identify the reducing agent in the displacement reaction. Give a reason for your answer. reducing agent _________________________________________ reason_________________________________________________

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What is the general term given to the type of reaction in which electrons are transferred from one species to another?

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The ionic equation for another displacement reaction is shown.

Pb (s) + 2Ag⁺ (aq) 2Ag (s) + Pb²⁺ (aq)

Write the two ionic half-equations for this reaction.

Use the information in (a) and (c) to put the three metals lead, nickel and silver in order of reactivity.