Formulae, Functional Groups & Terminology (Cambridge (CIE) IGCSE Chemistry): Exam Questions

The structures of six organic compounds are shown.

Give the name of F.

Separate: Chemistry Only

Identify two of the compounds that are members of the same homologous series.

Give the general formula of this homologous series.

compounds ..................................................

general formula ..................................................

Separate: Chemistry and Extended Only

Which two compounds are isomers of each other?

Explain why they are isomers.

compounds ........................................................................

explanation ........................................................................

Explain why B is an unsaturated hydrocarbon.

Extended Only

Describe how D is manufactured from B. Give a chemical equation for the reaction.

Extended Only

Compound A forms an addition polymer.

Draw two repeat units of the addition polymer formed from A.

Separate: Chemistry and Extended Only

A hydrocarbon has the following structural formula.

i) State the molecular formula and the empirical formula of this hydrocarbon.

 molecular formula ........................................................

 empirical formula ........................................................

 [2]

 ii) Draw the structural formula of an isomer of the above hydrocarbon.

 [1]

 iii) Explain why these two hydrocarbons are isomers.

 [2]

 iv) Are these two hydrocarbons members of the same homologous series? Give a reason for your choice.

 [1]

Alkenes can be made from alkanes by cracking.

 i) Explain the term cracking.

 [2]

 ii) One mole of an alkane, when cracked, produced one mole of hexane, C₆H₁₄, and two moles of ethene.

 What is the molecular formula of the original alkane?

 [1]

Extended Only

Alkenes are used in polymerisation reactions and addition reactions.

 i) Draw the structural formula of the product formed by the addition polymerisation of but-2-ene. Its formula is given below.

[3]

 ii) Give the name and structural formula of the addition product formed from ethene and bromine.

 name ..............................................................

 structural formula ..............................................................

 [2]

Extended Only

The alcohols form a homologous series. The first five members are given in the table below.

i) Complete the table. 

[2]

 ii) Complete the equation for the combustion of pentan-1-ol in excess oxygen.

C₅H₁₁OH + .......O₂ → ..................... + .....................

 [1]

Extended Only

State three characteristics of a homologous series other than the variation of physical properties down the series.

Separate: Chemistry and Extended Only

The following alcohols are isomers.

 CH₃–CH₂–CH₂–CH₂–OH   and   (CH₃)₂CH–CH₂–OH

i) Explain why they are isomers.

 [2]

 ii) Draw the structural formula of another isomer of the above alcohols.

 [1]

Extended Only

Alcohols can be made by fermentation and from petroleum.

 i) Ethanol is made from sugars by fermentation.

 C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

 The mass of one mole of glucose, C₆H₁₂O₆, is 180 g.

 Calculate the maximum mass of ethanol which could be obtained from 72 g of glucose.

 [3]

 ii) Describe how ethanol is made from petroleum.

 petroleum (alkanes) → ethene → ethanol

 [3]

Extended Only

The alcohols form a homologous series.

Give three characteristics of a homologous series.

Separate: Chemistry and Extended Only

The following two alcohols are members of an homologous series and they are isomers.

 CH₃―CH₂―CH₂―CH₂―OH   and   (CH₃)₂CH―CH₂―OH

 i) Explain why they are isomers.

 [2]

 ii) Deduce the structural formula of another alcohol which is also an isomer of these alcohols.

[1]

Separate: Chemistry and Extended Only

Copper(II) oxide can oxidise butanol to liquid X, whose pH is 4.

i) Give the name of another reagent which can oxidise butanol.

 [1]

 ii) Which homologous series does liquid X belong to?

 [1]

 iii) State the formula of liquid X.

 [1]

Separate: Chemistry and Extended Only

The alcohol ethanol can be made by fermentation. Yeast is added to aqueous glucose.

C₆H₁₂O₆ (aq) → 2C₂H₅OH (aq) + 2CO₂ (g)

Carbon dioxide is given off and the mixture becomes warm, as the reaction is exothermic. The graph shows how the rate of reaction varies over several days.

i) Suggest a method of measuring the rate of this reaction.

 [2]

 ii) Why does the rate initially increase?

 [1]

iii) Suggest two reasons why the rate eventually decreases.

 [2]

Extended Only

Methanoic acid is the first member of the homologous series of carboxylic acids.

Give two general characteristics of a homologous series.

Extended Only

In some areas when water is boiled, the inside of kettles become coated with a layer of calcium carbonate. This can be removed by adding methanoic acid.

 i) Complete the equation.

 ............ HCOOH + CaCO₃ → Ca(HCOO)₂ + ................. + .................

 [2]

 ii) Methanoic acid reacts with most metals above hydrogen in the reactivity series.

 Complete the word equation.

 zinc + methanoic acid → ................................. + ..................................

 [2]

Separate: Chemistry and Extended Only

Give the name, molecular formula and empirical formula of the fourth acid in this series.

name ..................................................

 [1]

 molecular formula ..................................................

 [1]

 empirical formula ..................................................

 [1]

Extended Only

Two homologous series of hydrocarbons are the alkanes and the alkenes.

One general characteristic of a homologous series is that the physical properties vary in a predictable way.

i) State three other general characteristics of a homologous series.

 [3]

 ii) How can the molecular formula of a hydrocarbon show whether it is an alkane or an alkene?

 [2]

 iii) How do alkanes and alkenes differ in their molecular structures?

 [2]

Cracking is the thermal decomposition of alkanes into smaller hydrocarbons and possibly hydrogen.

 i) State two conditions required for the cracking of an alkane.

 [2]

 ii) One type of cracking produces an alkane and an alkene.

 Complete an equation for the cracking of heptane into an alkane and an alkene.

 C₇H₁₆ → ................ + ................

 [1]

 iii) Complete an equation for the cracking of heptane into hydrogen and two other products.

 C₇H₁₆ → ................ + ................ + H₂

 [1]

 iv) Suggest one reason why cracking is important.

 [1]

Petrol is a mixture of hydrocarbons and additives. The combustion of petrol in car engines is a major source of air pollution. This is reduced by catalytic converters.

Petrol is obtained from the gasoline fraction, boiling point range 40 °C to 100 °C, from the distillation of petroleum.

Explain the term fraction.

Extended Only

In many countries, a lead compound of the type Pb(C₂H₅)_n used to be added to petrol to improve its combustion. After combustion, lead oxide was formed.

i) Octane is a constituent of petrol. Write the equation for the complete combustion of octane.

 C₈H₁₈ + .......... O₂ → .......... + ..........

[2]

 ii) Dibromoethane was added to petrol to remove the lead oxide from inside the engine. Lead bromide was formed which escaped into the environment through the exhaust. Leaded petrol cannot be used with a catalytic converter.

 Give another reason why leaded petrol is no longer used.

 [1]

 iii) What does each of the following tell you about the structure of dibromoethane?

 dibromo ..........................................................................................................

 eth ..........................................................................................................

 ane ..........................................................................................................

 [2]

 iv) What additional information is needed to draw the structural formula of dibromoethane?

 [1]

Extended Only

An analysis of the compound, Pb(C₂H₅)_n, showed that 0.026 moles of Pb was combined with 0.104 moles of C₂H₅ groups.

What is the value of n? Show how you arrived at your answer.

Extended Only

Some of the pollutants emitted by vehicle exhausts are carbon monoxide, oxides of nitrogen and unburnt hydrocarbons. Explain how the emission of these gases is reduced by a catalytic converter.

Extended Only

Methanoic acid is the first member of the homologous series of carboxylic acids.

Give two general characteristics of a homologous series.

Extended Only

In some areas when water is boiled, the inside of kettles become coated with a layer of calcium carbonate. This can be removed by adding methanoic acid.

i) Complete the equation.

............ HCOOH + CaCO₃ → Ca(HCOO)₂ + ................. + .................

[2]

ii) Methanoic acid reacts with most metals above hydrogen in the reactivity series. Complete the word equation.

zinc + methanoic acid → ............................................ + ............................................

[2]

iii) Aluminium is also above hydrogen in the reactivity series.

Why does methanoic acid not react with an aluminium kettle?

[1]

Separate: Chemistry and Extended Only

Give the name, molecular formula and empirical formula of the fourth acid in this series.

name ..........................................................................................................

[1]

molecular formula .......................................................................................................

[1]

empirical formula ........................................................................................................

[1]

Alkynes and alkenes are homologous series of unsaturated hydrocarbons. All alkynes contain a C≡C triple bond.

Complete Table 10.1 showing information about the first three alkynes.

Table 10.1

Extended Only

Compounds in the same homologous series have the same general formula.

Give two other characteristics of members of a homologous series.

Separate: Chemistry Only

Deduce the general formula of alkynes. Use the information from Table 10.1 to help you.

Alkynes are unsaturated.

Describe a test for unsaturation.

test   ........................

result ........................ 

Separate: Chemistry and Extended Only

Ethene and but-2-ene are alkenes. Draw the displayed formula of but-2-ene.

Extended Only

Draw a dot-and-cross diagram to show a molecule of ethene, CH₂=CH₂. Show outer shell electrons only.

Separate: Chemistry and Extended Only

Propane reacts with chlorine in a photochemical reaction as shown.

Draw two structural isomers of compounds with the formula C₃H₇Cl.

Show all of the atoms and all of the bonds.

There are three functional groups in compound A.

Name the homologous series of compounds that contains the following structures.

C=C       ...............................
–OH       ..............................
–COOH ...............................

Extended Only

Compound A can be used as a single monomer to produce two different polymers.

Draw one repeat unit of the addition polymer formed from compound A.

The structure of compound S is shown.

Draw a circle around the carboxylic acid functional group in this structure.

How many different types of atom are shown in this structure?

Ethanol can be converted into ethene by passing ethanol vapour over a catalyst of aluminium oxide.

Draw the structure of a molecule of ethanol. Show all of the atoms and all of the bonds.

The structures of five alkenes, A, B, C, D and E, are shown.

What is the general formula of alkenes?

Extended Only

Two different alcohols can be produced from alkene B by an addition reaction.

Draw the structures of the two alcohols. Show all of the atoms and all of the bonds.

The structure of myrcene is shown.

Deduce the formula of myrcene to show the number of atoms of carbon and hydrogen.

Myrcene is an unsaturated hydrocarbon. Describe a chemical test to distinguish between a saturated and an unsaturated hydrocarbon.

test ...................................
observations with saturated hydrocarbon .............................................
observations with unsaturated hydrocarbon .........................................

Butane is a saturated hydrocarbon.

To which homologous series does butane belong?

Draw a circle around the correct answer.

alcohol                    alkane                   alkene                   carboxylic acid

Alkanes and alkenes are examples of hydrocarbons.

i) What is meant by the term hydrocarbon?

[1]

ii) Give the general formula of straight-chain

alkanes.

alkenes. 

[2]

A compound X contains carbon, hydrogen and oxygen only.

X contains 54.54% of carbon by mass, 9.09% of hydrogen by mass and 36.37% of oxygen by mass.

i) Calculate the empirical formula of compound X.

[2]

ii) Compound X has a relative molecular mass of 88.

Deduce the molecular formula of compound X.

[2]

Extended Only

An ester has the molecular formula C₃H₆O₂.

Name and give the structural formulae of two esters with the molecular formula C₃H₆O₂.

Separate: Chemistry and Extended Only

Name the ester produced from the reaction of propanoic acid and methanol.

Separate: Chemistry and Extended Only

A polyester is represented by the structure shown.

i) What type of polymerisation is used for the production of polyesters?

[1]

ii) Which simple molecule is removed when the polyester is formed?

[1]

iii) Complete the diagrams below to show the structures of the monomers used to produce the polyester. Show all atoms and bonds.

[2]

Propanoic acid is a carboxylic acid. Its formula is CH₃–CH₂–COOH.

Propanoic acid is the third member of the homologous series of carboxylic acids.

 i) Give the name and structural formula of the fourth member of this series.

name ...............................................................

formula ...............................................................

 [2]

 ii) Members of a homologous series have very similar chemical properties.

 State three other characteristics of a homologous series.

 [3]

Carboxylic acids can be made by the oxidation of alcohols.

 i) Draw the structural formula of the alcohol which can be oxidised to propanoic acid. Show all atoms and bonds.

 [1]

 ii) Name a reagent, other than oxygen, which can oxidise alcohols to carboxylic acids.

 [2]

Complete the following equations for some of the reactions of propanoic acid.

 The salts of this acid are called propanoates.

i) zinc + propanoic acid → .................... .................... + hydrogen

 [1]

 ii) calcium oxide + propanoic acid → .................... .................... + ...........................

 [1]

 iii) LiOH + CH₃CH₂COOH → .................... + .................... 

 [1]

A piece of magnesium was added to 100 cm³ of an aqueous acid. The time taken for the metal to react completely was measured. This experiment was repeated using different aqueous acids. The same volume of acid was used in each experiment and the pieces of magnesium used were identical. In one experiment the reaction was carried out at a different temperature.

Explain the following in terms of collision rate between reacting particles.

i) Why is the rate in experiment C slower than the rate in experiment A?

 [2]

 ii) Why is the rate in experiment B faster than the rate in experiment A?

 [2]

 iii) Why is the rate in experiment D faster than the rate in experiment A?

 [3]

The alcohols form a homologous series. The first member is methanol and the fourth is butanol.

i) Give two general characteristics of a homologous series.

 [2]

 ii) Calculate the mass of one mole of the C₈ alcohol.

 [2]

Give the name and structural formula of the third member of this series.

 name ..................................................

 [1]

 structural formula ..................................................

 [1]

The structural formula of the fifth member, pentan-1-ol, is drawn below.

CH₃–CH₂–CH₂–CH₂–CH₂–OH

 i) Draw the structural formula of an isomer of this alcohol.

 [1]

 ii)Predict the names of the product(s) formed when pentan-1-ol

• reacts with an excess of oxygen,

   ....................................... and .......................................

 [1] 

• is dehydrated to form an alkene,

   ..................................................

[1] 

• is oxidised by acidified potassium dichromate(VI).

    ..................................................

 [1]

Butane is oxidised to a mixture of carboxylic acids by oxygen in the presence of a catalyst. The acids formed are methanoic acid, ethanoic acid and propanoic acid – the first three members of the carboxylic acid homologous series.

i) Give the name and structural formula of the fourth member of this series.

name ..........................................................................................................

 structural formula showing all the atoms and bonds

 [3]

ii) State three characteristics of a homologous series.

 [3]

 iii) All members of this series are weak acids.

 What is meant by the term weak acid?

 [3]

Carboxylic acids react with alcohols to form esters. Ethanol reacts with ethanoic acid to form the ester ethyl ethanoate, CH₃COOCH₂CH₃.

 i) Give the name and formula of the ester which is formed from methanol and propanoic acid.

 name ..........................................................................................................

 formula ..........................................................................................................

 [2]

 ii) What is the name of the ester which has the formula CH₃COOCH₃?

 [1]

i) Complete the equation for the oxidation of butane to propanoic acid.

 3C₄H₁₀ + .........O₂ → 4C₂H₅COOH + .......H₂O

 [1]

 ii) Name another compound which can be oxidised to propanoic acid.

 [1]

Butane is an alkane. It has the following structural formula

The equation for the complete combustion of butane is given below. Insert the two missing volumes.

 2C₄H₁₀ (g) + 13O₂ (g)  → 8CO₂ (g)  + 10H₂O (g)

volume of gas / cm³ ..........  ..........  40

Butane reacts with chlorine to form two isomers of chlorobutane.

 i) What type of reaction is this?

 [1]

 ii) Explain the term isomer.

 [2]

 iii) Draw the structural formulae of these two chlorobutanes.

 [2]

One of the chlorobutanes reacts with sodium hydroxide to form butan-1-ol. Butan-1-ol can be oxidised to a carboxylic acid.

 i) State a reagent, other than oxygen, which will oxidise butan-1-ol to a carboxylic acid.

[1]

 ii) Name the carboxylic acid formed.

 [1]

 iii) Butan-1-ol reacts with ethanoic acid to form an ester. Name this ester and give its structural formula showing all the individual bonds.

 name ..........................................................................................................

[1]

structural formula

[2]

The table shows some information about aldehydes.

Complete the table.

Deduce the general formula of aldehydes.

The structural formula of ethanal is shown.

The C=O group in aldehydes is at the end of the carbon chain. This is a reactive part of the molecule.

What is the name given to the reactive part of any organic molecule?

Propanone belongs to a homologous series called ketones. Ketones have the same C=O group as aldehydes but the C=O group is not at the end of the carbon chain. Propanone has the same molecular formula as propanal, C₃H₆O.

What term is used to describe molecules with different structures but with the same molecular formula?

Suggest the structure of propanone, C₃H₆O. Show all of the atoms and all of the bonds.