Properties of metals & alloys

Silver nitrate and potassium chloride are ionic compounds that are soluble in water.

When potassium chloride solution is added to a solution of silver nitrate, a white precipitate forms.

Complete the equation for this reaction, including the missing state symbol.

Give the name of the white precipitate that forms.

State and explain how the white precipitate can be separated from the reaction mixture.

Silver nitrate solution conducts electricity. Solid silver also conducts electricity.

Describe how silver nitrate solution conducts electricity and how solid silver conducts electricity.

A bottle containing an unknown solution is labelled with the two hazard symbols shown in Figure 16.

What are the meanings of these two symbols?

State a safety step that should be taken when using the unknown solution.

Silver nitrate and potassium chloride are ionic compounds that are soluble in water.

When potassium chloride solution is added to a solution of silver nitrate, a white precipitate forms.

Complete the equation for this reaction, including the missing state symbol.

Give the name of the white precipitate that forms.

State and explain how the white precipitate can be separated from the reaction mixture.

Silver nitrate solution conducts electricity. Solid silver also conducts electricity.

Describe how silver nitrate solution conducts electricity and how solid silver conducts electricity.

A student investigated the rusting of iron rods using the following method.

step 1 find the mass of two identical iron rods

step 2 wrap magnesium ribbon around one of the iron rods

step 3 place each rod in separate boiling tubes containing 10 cm3³ of water

step 4 leave the iron rods for one week

step 5 find the new mass of the iron rods.

Figure 10 shows the apparatus used.

Figure 11 shows the results of the investigation.

Use the results in Figure 11 to calculate the percentage increase in the mass of the iron rod in boiling tube B.

percentage increase in mass of iron rod =_........

Which gas from the air has reacted with the iron rod in boiling tube B ?

The iron rod did not rust in boiling tube A.

Explain why.

*(b) Figure 12 shows some uses of copper metal.

Describe how the properties of copper metal make it a suitable material for the uses shown.

Your answer should include

• uses of copper metal shown in the photographs

• properties of copper metal including:

– chemical reactivity

– electrical conductivity

– malleability

– thermal conductivity

Most of the gold used in jewellery is not pure gold but alloys of gold.

The purity of gold is measured in carats.

Figure 3 shows how the percentage of gold is related to the purity of gold measured in carats.

State the relationship between the percentage of gold and the number of carats.

Figure 4 shows the arrangement of atoms in pure gold and in an alloy of gold.

Using Figure 4, explain why alloys of gold are stronger than pure gold.

Explain one property of alloys of gold, other than their strength, that makes them suitable for use in jewellery.

Buildings sometimes have water sprinklers to put out fires.

The pipes in some water sprinklers are filled with nitrogen gas to prevent corrosion when the system is not in use.

State what is meant by the term corrosion.

Nitrogen can be made from sodium azide, NaN₃.

Calculate the maximum volume, in cm³, of nitrogen produced from 110 g of sodium azide.

(relative formula mass: NaN₃ = 65;

1 mol of gas occupies 24 dm³ in the conditions used)

*(b) Compare and contrast the properties and uses of pure aluminium and pure copper with the alloys of aluminium and the alloys of copper.

Include in your answer an explanation of the similarities and the differences in the properties and the uses of a pure metal and its alloy.

Magnesium carbonate has the formula MgCO₃.

Magnesium carbonate contains Mg²⁺ and CO₃²⁻ ions.

The atomic number of magnesium is 12.

What is the electronic configuration of the Mg²⁺ ion?

Explain why solid magnesium carbonate cannot conduct electricity but solid magnesium can.

Calculate the percentage by mass of magnesium in magnesium carbonate, MgCO₃.

(relative atomic masses: C = 12.0, O = 16.0, Mg = 24.0)

*(c) A student has two separate test tubes containing sulfuric acid.

The student adds a spatula measure of magnesium carbonate, MgCO₃, to the first test tube and a piece of magnesium to the second test tube.

Explain what the student would see in each test tube and the tests that they should carry out to identify the gases produced.

Your answer should include word equations for the reactions that would take place.

This question is about the metal gold.

Gold can be hammered into shape.

State the name of this property.

Gold alloys can be used to repair teeth. One reason that gold alloys are used is that they can be hammered into shape.

Give one other reason why gold alloys are used to repair teeth.

A gold alloy contains 78 % gold by mass.

Calculate the mass of gold in 2.00 kg of this alloy. Give your answer in grams.

A substance used to purify gold is kept in a container. There are some hazard symbols on the container.

Draw one straight line from each hazard symbol to its meaning.

*(d) Some gold alloys contain copper.

Copper reacts with oxygen when heated.

copper + oxygen copper oxide

A teacher calculates that 1.20 g of copper reacts completely with oxygen to form 1.50 g of copper oxide.

A student heats 1.20 g of copper pieces in a container. Then they heat 1.20 g of copper powder in another container. After heating, the mass of the solid in the containers is found.

The results are shown in Figure 7.

Explain the observations and give reasons why the masses after heating are less than expected.

Aluminium alloys are used instead of pure aluminium in aircraft manufacture.

Explain, in terms of the arrangement of metal particles, why aluminium alloys are stronger than pure aluminium.

A 695.0 g sample of an aluminium-magnesium alloy contains 2.00 % by mass of magnesium.

Calculate the mass of aluminium in this sample.

mass of aluminium =_........

Figure 12 shows a graph of the relative strength of aluminium-magnesium alloys when the percentage by mass of magnesium in the alloy is changed.

percentage by mass of magnesium in alloy

Figure 12

Describe what Figure 12 shows about the relative strength of these alloys when the percentage by mass of magnesium changes.

Determine, using Figure 12, the percentage by mass of aluminium in an aluminium‑magnesium alloy with a relative strength of 103.

percentage by mass of aluminium =_........

Metal objects can be electroplated with gold.

Give two reasons why metal objects are electroplated with gold.

Iron rusts when it is left in certain conditions.

Figure 9 shows the apparatus used to investigate the rusting of some iron nails.

Explain why the iron nail in tube A would rust but the iron nails in tubes B and C would not rust.

Magnesium is more reactive than iron. Figure 10 shows an iron nail with a strip of magnesium wrapped around it, placed in some water. The tube was left for a few days.

State what would happen to this iron nail.

When iron rusts, a brown solid forms on the surface of the iron.

What happens to the iron as the rust forms?

Give one reason why metals are electroplated.

*(c) The pure metals aluminium, copper and gold and the alloys brass and magnalium are used to make many useful articles.

The way in which these metals and alloys are used is related to their properties, such as their density, electrical conductivity, resistance to corrosion and strength.

State some uses of aluminium, copper, gold, brass and magnalium and explain how each use is related to their properties.

7 *(a) Pure metals are often converted into more useful alloys. For example, aluminium is converted into an alloy used in aircraft, iron is converted into an alloy used in cutlery and gold alloys are used in jewellery. These processes of alloying change the structures of the metals.

Some properties of pure aluminium, iron and gold are shown in Figure 12.

Explain how alloying changes these pure metals to make the alloys more suitable for the given uses.

Iron objects can corrode when exposed to the atmosphere.

Corrosion involves the oxidation of iron.

State what is meant by oxidation.

Painting iron objects prevents corrosion.

Explain why painting iron objects prevents corrosion.

Corrosion of iron objects can be prevented by painting them or by electroplating them.

State one other way of preventing the corrosion of iron objects.

The apparatus shown in Figure 13 was used to electroplate a spoon with nickel.

State to what the anode and cathode have to be connected in order to carry out the electroplating.

Predict the name of a substance that could be dissolved in water to form the electrolyte for this electroplating.