Alloys & their Properties (Cambridge (CIE) O Level Chemistry): Exam Questions

Iron from the blast furnace is impure. It contains about 4% carbon and 0.5% silicon. Most of this impure iron is used to make mild steel, an alloy of iron containing less than 0.25% carbon.

A jet of oxygen is blown through the molten iron in the presence of a base, usually calcium oxide. Explain how the percentage of carbon is reduced and how the silicon is removed. 

i) Why are steel alloys used in preference to iron?

[1]

ii) State a use of the following alloy.

Stainless steel

[1]

Both iron and steel have typical metallic structures - a lattice of positive ions and a sea of electrons.

i) Suggest an explanation for why they have high melting points.

[2]

ii) Explain why, when a force is applied to a piece of steel, it does not break but just changes its shape.

[2]

Vanadium is a transition element.

An atom of the most common isotope of vanadium can be represented as ${}_{23}{}^{51}\mathrm{V}$.

Complete the following table to show the number of protons, electrons and neutrons in each particle.

The major use of vanadium is to make vanadium steel alloys. 

i) Explain the phrase steel alloys.

[2]

ii) State the name and use of another steel alloy.

[2]

Two of the oxidation states of vanadium are +3 and +4.

i) Write the formula of vanadium(III) oxide and of vanadium(IV) oxide.

[2]

ii) Vanadium(III) oxide is basic and vandium(IV) oxide is amphoteric.
Describe how you would obtain a sample of vanadium(III) oxide from a mixture of these two oxides.

[3]

The table shows the composition and the hardness of three different types of brass.

Use the table to explain why brass cannot be represented by a chemical formula.

i) Describe how the hardness of brass changes as the percentage of zinc increases.

[1]

ii) Ship fittings must not bend or dent when they are struck by waves.

Suggest which brass, A, B or C, is the most suitable for making ship fittings.

Give a reason for your choice.

[2]

A fourth type of brass contains 85% copper.

i) Deduce the percentage of zinc in this brass.

[1]

ii) Predict how the hardness of this fourth brass compares with the hardness of brass A.

Give a reason for your prediction.

[2]

An iron nail is coated with a thin layer of zinc.

A door handle is made from brass, which contains copper and zinc.

State which of these two objects is made from an alloy.

Explain, by referring to both the nail and the door handle, why only one of them is made from an alloy.

i) State one property of brass that makes it suitable for a door handle.

[1]

ii) Suggest two reasons why pure copper would be less suitable than brass for a door handle.

[2]

Solder is an alloy of tin and lead.

The table shows the melting points of tin, lead and solder.

i) State the melting point of solder.

[1]

ii) Describe how the melting point of solder compares with the melting points of the two pure metals it contains.

[1]

Solder is used to join electrical components to a circuit board.

i) Describe how solder is used to join two electrical components together.

[2]

ii) Suggest why solder is more suitable for this job than pure lead would be.

[1]

Lead is poisonous. Modern solder contains tin and silver instead of tin and lead.

Tin-silver solder melts at 221 °C.

i) Suggest one advantage of using tin-silver solder rather than tin-lead solder.

[1]

ii) Suggest one disadvantage of using tin-silver solder rather than tin-lead solder for joining electrical components.

[2]

Cutlery is made from stainless steel rather than from pure iron.

i) State two properties of stainless steel that make it suitable for making cutlery.

[2]

ii) Explain why one of these properties is particularly important for a knife blade.

[1]

Stainless steel is also used to make kitchen sinks.

Suggest two reasons why stainless steel is suitable for making a kitchen sink.

Surgical instruments are made from stainless steel. They are heated to high temperatures to sterilise them and are then used again.

A manufacturer suggests making surgical instruments from brass instead.

Suggest two reasons why brass would be less suitable than stainless steel for making surgical instruments.

The list shows the names of some metals.

calcium

copper

iron

magnesium

silver 

zinc

i) Identify the metal from the box that burns with a bright white flame.

[1]

ii) In the Earth, metals are found either in ores or as uncombined elements. Explain which metal from the box is most likely to be found as an uncombined element.

[2]

i) Which metal or metals from the list in part (a) will react readily in oxygen?

[2]

ii) Give an equation to show a metal reacting with oxygen. Include state symbols.

[2]

The diagram shows the arrangement of the particles in a pure metal.

Metals are often made into alloys to make them harder.

Explain why alloys are harder than pure metals.

Draw a diagram to support your answer.

Complete the table by naming two alloys and giving the elements used to make each alloy.

Tungsten is a useful metal. It has the chemical symbol W.

One method of extracting tungsten involves heating a tungsten compound, WO₃, with hydrogen. Water is also produced. Write the balanced symbol equation for this reaction.

Identify what has been reduced. Give a reason for your answer.

Tungsten alloyed with nickel and copper can be used to make protective covers for electrical sensors and missile guidance systems. Explain why this alloy is stronger than pure tungsten.

An ore of tungsten is Scheelite. The composition of this ore is 13.9% of calcium, 63.9% of tungsten and the remainder is oxygen. Calculate the empirical formula for this ore of tungsten.

Steel is formed from iron and carbon and is widely used in the construction industry.

i) Explain why steel alloys are used in preference to iron.

[1]

ii) State a use of stainless steel.

[1]

Both iron and steel have typical metallic structures - a lattice of positive ions and a sea of electrons.

i) Explain why iron and steel have high melting points.

[2]

ii) Explain why, when a force is applied to a piece of steel, it does not break but changes its shape.

[2]

Brass is an alloy of two metals, copper and zinc.

Which statement is correct?

Tick one box.

Acid digestion is a method used to dissolve metals into a solution which can then be analysed to determine the composition of the metal.

A 3.00 g sample of an aluminium alloy was reacted with an excess of concentrated nitric acid. The resulting mixture was made up to 250 cm³ with distilled water and analysed. The concentration of aluminium ions in the 250 cm³ solution was found to be 0.36 mol/dm³.

Calculate the percentage composition by mass of aluminium in the 3.00 g sample of aluminium alloy.

[A_r (Al) = 27]

The pins of an electrical plug are made from brass, which is an alloy of copper and zinc.

The pins must conduct electricity well.

State what is present in brass that allows it to conduct electricity.

Explain how this allows a current to flow.

A student says that because the layers of atoms in brass cannot slide over each other easily, brass cannot conduct electricity.

Explain why the student is wrong.

The table shows the electrical conductivity of copper, zinc and brass, given as a percentage of the conductivity of copper.

i) State which of the three metals in the table has the lowest electrical conductivity.

[1]

ii) Suggest why the pins of a plug are made from brass even though copper conducts electricity better.

[2]

The wiring inside a house is made from copper rather than from brass. Several hundred metres of wire are needed to wire a house.

Suggest why brass would be unsuitable for the wiring inside a house.

The table shows some properties of three alloys, P, Q and R.

A manufacturer needs an alloy for a bicycle frame. The frame must be light and strong, and must not corrode when the bicycle is left outside.

Suggest which alloy, P, Q or R, is the most suitable.

Give two reasons for your choice.

Give two disadvantages of using alloy Q for bicycle frames.

Alloy R is used for the frameworks of large bridges.

Suggest why alloy R is suitable for this use even though it has poor resistance to corrosion.

A manufacturer makes several different versions of alloy P, each containing different proportions of the same metals.

Suggest why the manufacturer does this.

Copper can be alloyed with zinc, with nickel or with tin.

The table shows the atomic radius of each of these four metals.

State which of zinc, nickel and tin has the atomic radius closest to that of copper.

Each of the three alloys contains the same percentage of the second metal.

Predict which of the three alloys, copper with zinc, copper with nickel or copper with tin, would be the hardest.

Explain your prediction in terms of the sizes of the atoms.

An alloy of copper containing a small percentage of nickel is only slightly harder than pure copper.

Explain why, using the data in the table.

Coins are made from an alloy of copper and nickel rather than from an alloy of copper and tin.

Suggest two reasons why an alloy of copper and nickel might be chosen for coins even though it is less hard.