Metals & Their Extraction (WJEC GCSE Science (Double Award): Chemistry): Flashcards

False.

Metals above carbon in the reactivity series must be extracted by electrolysis, not by reduction with carbon. Only metals below carbon can be reduced using carbon.

Gold and silver are described as native metals because they are found as uncombined elements in the Earth's crust.

These metals are above carbon in the reactivity series. Carbon cannot reduce them because it is not reactive enough, so electrolysis of their molten chloride or oxide is required instead.

Zinc and iron are both below carbon in the reactivity series and can be extracted by reduction with carbon or carbon monoxide.

False.

Electrolysis requires a large amount of electricity, making it an expensive process. It is used only when reduction with carbon is not possible.

The method used to extract a metal depends on its position in the reactivity series. Metals higher up must be extracted by electrolysis.

Gold is a very unreactive metal and does not easily react with other substances. It is found as an uncombined (native) element in the Earth's crust, so it can be mined directly without chemical extraction.

The reactivity series is a list of metals arranged in order of decreasing reactivity, based on how readily each metal loses electrons when it reacts.

In a displacement reaction, a more reactive metal will displace a less reactive metal from its compounds.

True.

Although carbon and hydrogen are non-metals, they are included because they can reduce metal oxides to extract metals. Their position in the series determines which metals they can extract.

The products are magnesium sulfate (MgSO₄) and copper (Cu). Magnesium is more reactive than copper, so it displaces copper from the solution.

Mg + CuSO₄ → MgSO₄ + Cu

The blue colour of the copper sulfate solution fades as colourless magnesium sulfate forms. Copper metal coats the surface of the magnesium and falls to the bottom of the beaker.

The thermite reaction occurs when iron(III) oxide reacts with aluminium. The products are iron and aluminium oxide.

Fe₂O₃ + 2Al → 2Fe + Al₂O₃

False.

Sodium is above zinc in the reactivity series, so zinc cannot displace sodium. A more reactive metal is needed to displace a less reactive one.

Metals higher up the reactivity series have a greater tendency to lose electrons and form positive ions. The easier a metal loses electrons, the more reactive it is.

Word equation: iron + copper(II) sulfate → iron(II) sulfate + copper

Symbol equation: Fe + CuSO₄ → FeSO₄ + Cu

A displacement reaction occurs when a more reactive metal takes the place of a less reactive metal in a compound, removing it from the solution or compound.

In the specified practical, metals are added to aqueous solutions of metal salts using a dimple tile.

A different pipette is used for each solution to avoid contamination between the different metal salt solutions, which would affect the results.

True.

Magnesium is the most reactive metal in the practical. It displaces zinc, copper and iron from their sulfate solutions because it is more reactive than all three.

A reaction does occur because zinc is more reactive than copper.

zinc + copper(II) sulfate → zinc sulfate + copper

Zn + CuSO₄ → ZnSO₄ + Cu

In the displacement practical, copper does not react with any of the sulfate solutions because it is the least reactive metal in the experiment.

1. Magnesium (most reactive)

2. Zinc

3. Iron

4. Copper (least reactive)

This order is determined by the number of displacement reactions each metal undergoes — the most reactive metal displaces the most others.

False.

Magnesium is more reactive than iron, so iron cannot displace magnesium from magnesium sulfate solution. No reaction occurs.

A metal cannot displace itself from its own compound. No displacement reaction occurs because both substances contain the same metal, so there is no difference in reactivity to drive a reaction.

Oxidation is a reaction in which oxygen is added to an element or compound.

Reduction is a reaction in which oxygen is removed from an element or compound.

Oxidation and reduction always occur together in the same reaction. These are called redox reactions.

False.

In this reaction, zinc oxide loses oxygen so it is reduced. The carbon gains oxygen to form carbon dioxide, so carbon is oxidised.

Iron(III) oxide is reduced because it loses oxygen to form iron. Carbon monoxide is oxidised because it gains oxygen to form carbon dioxide.

In the blast furnace, iron(III) oxide is reduced to iron. It is the iron(III) oxide that is reduced, not the iron itself.

The reaction is classified as a redox reaction because both oxidation and reduction occur simultaneously. Zinc oxide is reduced (loses oxygen) and carbon is oxidised (gains oxygen) in the same reaction.

True.

Because carbon is more reactive than iron, it can displace iron from its oxide by acting as the reducing agent in the blast furnace.

A blast furnace is a large industrial container used to extract iron from its ore (haematite) by reduction with carbon monoxide.

The three raw materials added to the top of the blast furnace are haematite (iron ore), coke (impure carbon) and limestone.

Word equation: carbon + oxygen → carbon dioxide

Symbol equation: C (s) + O₂ (g) → CO₂ (g)

This reaction is exothermic and heats the furnace.

False.

In Zone 2, carbon dioxide is reduced to carbon monoxide by reacting with more coke.

CO₂ (g) + C (s) → 2CO (g)

In Zone 3, carbon monoxide reduces iron(III) oxide to form molten iron. The iron collects at the bottom of the furnace.

Fe₂O₃ (s) + 3CO (g) → 2Fe (l) + 3CO₂ (g)

Iron(III) oxide is reduced by carbon monoxide to produce molten iron and carbon dioxide.

Limestone (calcium carbonate) thermally decomposes to form calcium oxide and CO₂. The calcium oxide then reacts with acidic silicon dioxide impurities to form calcium silicate (slag), which floats on the molten iron and is tapped off.

False.

It is iron(III) oxide that is reduced. Iron is the product of the reduction. This is a common exam error — always state that iron(III) oxide is reduced, not iron.

CaCO₃ (s) → CaO (s) + CO₂ (g)

Calcium carbonate decomposes into calcium oxide and carbon dioxide when heated in the blast furnace.

The blast furnace is run continuously because of the time and cost involved in bringing the furnace up to the required temperature. Stopping and restarting would be very expensive and inefficient.

An electrolyte is a liquid or solution that is able to conduct electricity. It contains free-moving ions, allowing charge to flow.

In electrolysis, the anode (positive electrode) attracts negative ions called anions.

In a solid ionic compound the ions are held in fixed positions and cannot move, so charge cannot flow. When molten, the ions are free to move and carry charge, allowing electrolysis to occur.

False.

Bromine gas is produced at the anode (positive electrode). At the cathode (negative electrode), lead metal is deposited.

During electrolysis of a molten binary compound, the metal is always produced at the cathode and the non-metal is always produced at the anode.

Pb²⁺ + 2e^– → Pb

Lead ions gain electrons (are reduced) to form lead metal at the cathode.

2Br^– → Br₂ + 2e^–

Bromide ions lose electrons (are oxidised) to form bromine gas at the anode.

False.

Covalent compounds do not contain free ions so they cannot conduct electricity and cannot undergo electrolysis. Only ionic compounds (when molten or dissolved) can be electrolysed.

Electrodes must be inert (e.g. graphite or platinum) so that they do not react with the electrolyte or the products. A reactive electrode could cause unwanted side reactions that interfere with the electrolysis.

Oxidation is the loss of electrons by a substance during a chemical reaction.

Reduction is the gain of electrons by a substance during a chemical reaction.

The mnemonic OIL RIG stands for: Oxidation Is Loss, Reduction Is Gain of electrons.

False.

Reduction (gain of electrons) takes place at the cathode. Oxidation (loss of electrons) takes place at the anode. Remember: RED CAT, AN OX.

Iron (Fe) is oxidised because it loses 2 electrons to become Fe²⁺. Cu²⁺ is reduced because it gains 2 electrons to become copper metal (Cu).

During electrolysis, positive ions move to the cathode where they gain electrons and are reduced.

Pb²⁺ + 2e^– → Pb

Lead ions gain 2 electrons and are reduced to form lead metal at the cathode.

True.

A redox reaction involves simultaneous oxidation (loss of electrons) and reduction (gain of electrons) in the same reaction.

2Br^– → Br₂ + 2e^–

Bromide ions lose electrons and are oxidised to form bromine gas at the anode.

Cryolite is the substance in which aluminium oxide is dissolved during electrolysis. It lowers the melting point of the mixture, making the process more energy efficient and less costly.

Aluminium cannot be extracted by reduction with carbon because it is above carbon in the reactivity series. Instead, it is extracted by electrolysis.

Aluminium oxide has a melting point of over 2000°C, which would require enormous amounts of energy and be very expensive. Dissolving it in molten cryolite lowers the melting point of the mixture without interfering with the electrolysis.

False.

Aluminium is produced at the cathode (negative electrode). Al³⁺ ions gain electrons and are reduced to form molten aluminium metal.

At the cathode: Al³⁺ + 3 e^– → Al

At the anode: 2O^2– → O₂ + 4e^–

Oxygen produced at the anode reacts with the graphite (carbon) anodes to form CO₂. This causes the anodes to gradually wear away and so they must be replaced.

True.

This is true because aluminium is more reactive than carbon, because it sits above carbon in the reactivity series, so carbon cannot displace it. Instead, aluminium is extracted by electrolysis of aluminium oxide dissolved in molten cryolite.

Electrolysis requires a large amount of electricity, which is a major expense in the extraction process. Energy is also needed to keep the electrolyte molten.

The cell is made from steel lined with graphite. The graphite lining acts as the cathode (negative electrode), with large graphite blocks acting as the positive electrodes (anodes).

1. Copper is an excellent conductor of electricity

2. Copper is malleable and ductile (can be drawn into wires)

These properties make it ideal for carrying electrical current through flexible wires.

Aluminium is used for overhead power cables because it has a low density, is a good conductor of electricity and is resistant to corrosion.

False.

Titanium has a low density. This, combined with its high strength, resistance to corrosion and high melting point, makes it suitable for spacecraft and medical implants.

A malleable material can be hammered or pressed into shape without breaking. Most metals are malleable, which makes them useful for construction and manufacturing.

Steel is used in buildings and cars because it is hard and strong, able to withstand large forces without deforming. Reinforced concrete also uses steel rods to increase structural strength.

Titanium is used in surgical instruments and joint replacements because it is strong, has a low density and is resistant to corrosion.

True.

Copper is malleable (can be shaped into pipes) and does not corrode easily. Its good thermal conductivity is also relevant for hot water systems.

Aluminium has a much lower density than steel, making aircraft significantly lighter. It is also strong and resistant to corrosion, so it maintains structural integrity without adding excessive weight.

Transition metals are a group of metals found in the centre of the Periodic Table. They have high melting points, high density and can form coloured compounds and act as catalysts.

Transition metals are useful as catalysts because they speed up the rate of chemical reactions. For example, iron is used as a catalyst in the Haber process.

False.

Transition metals can form more than one type of ion. For example, iron can form Fe²⁺ and Fe³⁺ ions.

1. High melting and boiling points

2. Malleable (can be hammered into shape)

3. High density

4. Good conductors of electricity and heat

Platinum is used in catalytic converters in car exhausts. It catalyses reactions that reduce levels of nitrous oxides and carbon monoxide produced by the engine.

Iron can form two types of ion: Fe²⁺ ions, which form pale green compounds, and Fe³⁺ ions, which form brown compounds. (Higher Tier Only)

True.

Copper(II) sulfate contains Cu²⁺ ions, which give the compound its characteristic blue colour. This is a typical property of transition metal compounds. (Higher Tier Only)

Transition metals can form more than one type of ion, each of which gives compounds a different colour. For example, Fe²⁺ compounds are pale green and Fe³⁺ compounds are brown. (Higher Tier Only)

An alloy is a mixture of two or more metals, or a metal mixed with a non-metal such as carbon. Alloys are not compounds.

Steel is an alloy made from iron and carbon. Stainless steel also contains chromium, nickel and carbon.

Alloys contain atoms of different sizes, which distorts the regular arrangement of atoms in the metal lattice. This makes it harder for the layers to slide over each other, so the alloy is harder than the pure metal.

False.

Brass is an alloy of copper and zinc. It is much stronger than either pure metal and is used in musical instruments, ornaments and door knobs.

1. Hardness — it is strong enough to withstand regular use

2. Resistance to corrosion — it does not rust or tarnish in contact with food or water

Aluminium alloys used for aircraft bodies contain copper, manganese and silicon. This gives the alloy greater strength while maintaining a low density.

False.

Alloys are mixtures, not compounds. The component metals are not chemically bonded and can be separated by physical means.

Iron-tungsten alloys are extremely hard and resistant to high temperatures. This makes them useful in high-temperature industrial applications such as cutting tools and drill bits.

Alloys contain atoms of different sizes, disrupting the regular metal structure. This can make them stronger, harder, more resistant to corrosion or better able to withstand high temperatures than the original pure metals.

Sustainability in metal extraction means meeting present needs while conserving resources and minimising environmental impact for future generations.

The most important factor in determining whether to extract a metal is whether it is economically viable. The financial gain must exceed the costs involved.

1. Raw materials

2. Energy

3. Labour costs

Extraction is only worthwhile if the financial return from the metal is greater than these combined costs.

False.

The main reason for coastal locations is to import raw materials. While exporting products is also a benefit, the primary driver is access to raw material imports.

Recycling aluminium requires approximately 5% of the energy needed to extract it from its ore, making it much more energy efficient.

Metal extraction (especially by electrolysis) requires large amounts of electricity. Being located near a power station reduces the cost and energy loss associated with transmitting electricity over long distances, making the process more economical.

True.

Recycling uses far less energy than primary extraction, reduces waste at landfill, lowers the carbon footprint and provides employment. It is economically beneficial for costly metals such as aluminium.

1. Good transport links (roads and rail) to import raw materials

2. Close to a power station for the large energy requirement

3. Near a populated area to provide a workforce but not so close that noise pollution is an issue

1. Use renewable energy sources to power the process

2. Recycle metals to reduce the need for primary extraction

3. Minimise waste and reduce the carbon footprint of the process