Oxidation and reduction in terms of electrons

Methane reacts with oxygen to make carbon dioxide and water.

Which chemical is being oxidised?

A CH₄

B CO₂

C H₂O

D O₂

Magnesium reacts with oxygen to make magnesium oxide.

Which type of reaction is shown by the equation?

A Displacement

B Electrolysis

C Neutralisation

D Oxidation

Carbon reacts with copper oxide to produce copper.

copper oxide + carbon copper + carbon dioxide

What is the role of the carbon?

A It is a catalyst.

B It neutralises the copper oxide.

C It oxidises the copper oxide.

D It reduces the copper oxide.

Aluminium is extracted from a rock called bauxite which contains aluminium oxide.

The diagram shows information from a life-cycle assessment for the manufacture and use of aluminium products.

Give one reason why a life-cycle assessment is carried out.

Give two reasons why the products should be recycled at the end of their useful life.

18% of the bauxite rock is turned into aluminium.

Calculate the mass of aluminium that is extracted from 7500 kg of bauxite.

Give your answer to 2 significant figures.

Aluminium is extracted from aluminium oxide, Al₂O₃, by electrolysis.

This is the equation for the electrolysis of aluminium oxide.

A student thinks that this reaction is an example of reduction.

Explain why the student is correct.

Extracting aluminium by electrolysis is expensive.

Which statements about why the electrolysis is expensive are true, and which are false ?

Tick one (✓) box in each row.

It would be cheaper if aluminium could be extracted by heating the aluminium oxide with carbon.

Explain why aluminium oxide does not react with carbon.

Carbon reacts with copper oxide to produce copper.

copper oxide + carbon copper + carbon dioxide

What is the role of the carbon?

A It is a catalyst.

B It neutralises the copper oxide.

C It oxidises the copper oxide.

D It reduces the copper oxide.

Aluminium is extracted from a rock called bauxite which contains aluminium oxide.

The diagram shows information from a life-cycle assessment for the manufacture and use of aluminium products.

Give one reason why a life-cycle assessment is carried out.

Give two reasons why the products should be recycled at the end of their useful life.

18% of the bauxite rock is turned into aluminium.

Calculate the mass of aluminium that is extracted from 7500 kg of bauxite.

Give your answer to 2 significant figures.

Aluminium is extracted from aluminium oxide, Al₂O₃, by electrolysis.

This is the equation for the electrolysis of aluminium oxide.

A student thinks that this reaction is an example of reduction.

Explain why the student is correct.

Extracting aluminium by electrolysis is expensive.

Which statements about why the electrolysis is expensive are true, and which are false ?

Tick one (✓) box in each row.

It would be cheaper if aluminium could be extracted by heating the aluminium oxide with carbon.

Explain why aluminium oxide does not react with carbon.

In industry, iron can be extracted from iron ore. Iron ore contains iron oxide, Fe₂O₃.

Iron is extracted from iron oxide by reduction.

The equation for one reaction is

Complete the balanced symbol equation for the reaction.

Why does this reaction happen?

Tick (✓) one box.

Explain how the equation shows that the iron oxide is reduced.

Which chemical reduces the iron oxide, Fe₂O₃?

Tick (✓) one box.

In industry, iron is extracted from iron ore in a blast furnace.

The table shows information about the production of iron in a blast furnace and from recycling.

Give two reasons why it is better to produce iron from recycling than in a blast furnace.

Use the information from the table.

Calculate the mass of iron made from 250 tonnes of iron ore in the blast furnace. Give your answer in kilograms.

(1 tonne = 1000 kg)

Iodine is an element in Group 7 of the Periodic Table.

Seaweed has small amounts of compounds containing iodine. It is possible to extract iodine from seaweed.

The diagram shows the stages in the extraction of iodine.

In Stage 1 iodide ions are produced by reduction.

Explain reduction in terms of electrons.

In Stage 2 iodide ions are oxidised to iodine.

Complete the half-equation for the oxidation of iodide ions into iodine.

In Stage 3 if the solution is heated for too long, iodine vapour is formed.

What colour is iodine vapour?

0.13 g of iodine is produced from 5.0 g of seaweed.

Calculate the percentage mass of iodine in the seaweed.

The equation shows the reaction between carbon dioxide, CO₂, and hydrogen, H₂.

What is the oxidising agent in the reaction?

A CO

B CO₂

C H₂

D H₂O

The equation shows the reaction between carbon dioxide, CO₂, and hydrogen, H₂.

What has been reduced in this reaction?

A CO

B CO₂

C H₂

D H₂O

Potassium chloride, KC l, is an ionic compound.

It is made from potassium ions, K +, and chloride ions, C l –.

Explain why potassium is found in Group 1 of the Periodic Table.

Use ideas about the arrangement of electrons in an atom of potassium.

Explain how an atom of potassium reacts with an atom of chlorine to make potassium chloride.

A student electrolyses potassium chloride.

The diagram shows the equipment they use.

Describe and explain two ways the student could change the experiment to make it work.

In the successful electrolysis of potassium chloride, potassium is made at the cathode.

Explain how potassium atoms are made from potassium ions.

Colour changes can be used to show that oxidation and reduction happen in chemical reactions.

The diagram shows the reaction between an acidic solution of vanadium(IV) oxide and zinc.

• As the reaction happens the colour of the solution turns from blue to green.

The balanced half equation shows the reaction of vanadium(IV) oxide.

A student thinks that the half equation shows that reduction has taken place.

Describe two ways in which the half equation shows the student is correct.

This half equation shows the reaction of the zinc.

Complete the half equation for the reaction.

The student removes the zinc from the green solution by filtration. When they add some nitric acid to this solution it turns back from green to blue.

What is the role of the dilute nitric acid in this reaction?

Tick one (✓) box.

Copper can form many different compounds.

The table shows the formulae of five different compounds of copper.

Which compound, A, B, C, D or E, is made from copper, carbon and oxygen?

Which compound, A, B, C, D or E, is made when copper is oxidised as copper reacts with oxygen?

Which compound, A, B, C, D or E, reacts with dilute hydrochloric acid to make carbon dioxide?

Calculate the relative formula mass of compound D.

The relative atomic mass, A_r, of Cu is 63.5 and of S is 32.1

Look at the ionic equation.

Which species is reduced ?

A Cu(s)

Cu²⁺(aq) B

C Mg(s)

Mg²⁺(aq) D

Iron can be made from the reaction of iron(III) oxide with carbon monoxide.

What is the reducing agent in this reaction?

A CO

B CO₂

C Fe

D Fe₂O₃

Explain the term electrolysis.

Electrolysis involves the reactions of cations and anions.

Describe the difference between cations and anions.

The electrolysis of molten potassium chloride makes potassium at the cathode.

Write the balanced half equation for the formation of potassium.

State and explain if this equation shows oxidation or reduction.

Name the product formed at the anode when an aqueous solution of potassium chloride, KC l (aq), is electrolysed.

Give a reason for your answer.

The diagram shows what happens when a small amount of potassium bromide solution, KBr, is added to a solution of chlorine, Cl₂.

Write the balanced symbol equation for the reaction between potassium bromide, KBr, and chlorine, Cl₂.

Write down the name of the chemical which makes the solution orange.

In this reaction is chlorine oxidised or reduced?

Explain your answer.

Explain why chlorine is more reactive than bromine.

A student investigates three reactions.

She wants to find out if the reactions are exothermic or endothermic.

Look at her results.

Which reaction, X, Y or Z, is endothermic ?........

Explain your answer.

Draw a labelled reaction profile for an endothermic reaction.

Use the following labels on your reaction profile:

• products

• energy change

• activation energy.

Another student repeats the same reactions.

The student does the experiment in a polystyrene cup instead of a beaker.

Explain why using a polystyrene cup is an improvement to the method.

The reaction between iron oxide and aluminium is very exothermic.

Look at the equation for the reaction.

During this reaction the aluminium is oxidised.

Explain what is meant by the term oxidised.

Pure iron metal is produced in the reaction.

Draw a diagram to show the bonding in a metal.

Label your diagram clearly.

One homologous series of organic compounds is called the alkanes.

They have the general formula C_nH_2n+2.

The alkane with one carbon atom, n = 1, is called methane.

Write down the formula of methane.

Table 13.1 shows the energy released when some alkanes burn in oxygen.

Plot a graph of number of carbon atoms against energy released using the data in Table 13.1 and draw a line of best fit.

Use the graph to predict the energy released when methane burns (1 carbon atom).

Energy released =........ kJ / mol

Hexane is a liquid alkane that burns in oxygen.

Which element in hexane is oxidised to produce water?

Give a reason for your answer.

A student burns 10.0 g of hexane.

These are his results.

Mass of hexane before burning = 10.0 g Mass of hexane after burning = 0.0 g

The law of conservation of mass is true for this reaction.

Explain why.

A student investigates three reactions.

She wants to find out if the reactions are exothermic or endothermic.

Look at her results.

Which reaction, X, Y or Z, is endothermic ?........

Explain your answer.

Draw a labelled reaction profile for an endothermic reaction.

Use the following labels on your reaction profile:

• products

• energy change

• activation energy.

Another student repeats the same reactions.

The student does the experiment in a polystyrene cup instead of a beaker.

Explain why using a polystyrene cup is an improvement to the method.

The reaction between iron oxide and aluminium is very exothermic.

Look at the equation for the reaction.

During this reaction the aluminium is oxidised.

Explain what is meant by the term oxidised.

Pure iron metal is produced in the reaction.

Draw a diagram to show the bonding in a metal.

Label your diagram clearly.