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

Exam Questions

4 hours42 questions
11 mark

The diagrams show part of the structures of five substances, A, B, C, D and E.

dFPHIipH_q1-0620_s19_qp_32

Which one of these structures, A, B, C, D or E is an alcohol?

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21 mark

The structure of nerol is shown below:

q7_0620-s20-qp-32_cie-igcse-chemistry

Draw a circle around the alcohol functional group in nerol.

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3a1 mark

One of the organic acids present in milk is lactic acid.

The displayed formula of lactic acid is shown in Fig. 2.2.

q2c_specimen-paper-0620-03-cie-igcse-chemistry

Fig. 2.2

Draw a circle around the carboxylic acid functional group on the structure. 

3b1 mark

Deduce the molecular formula of lactic acid.

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41 mark

The structure of nerol is shown.

i5ablJmz_q7_0620-s20-qp-32_cie-igcse-chemistry

What feature of the nerol molecule shows that it is an unsaturated compound?

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51 mark

Sulfur dioxide, SO2, is used in the manufacture of sulfuric acid.

When propan-1-ol is heated with concentrated sulfuric acid as a catalyst an unsaturated hydrocarbon of relative molecular mass 42 is formed and one other product.

What is meant by the term unsaturated?

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6a1 mark

Coal gas is made by heating coal in the absence of air. The list shows the main gases present in coal gas.

carbon dioxide
carbon monoxide
ethene
hydrogen
methane
nitrogen

Which one of these gases is an alkane?

6b1 mark

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

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7a1 mark

Methane, ethane and ethene are hydrocarbons.

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

7b1 mark

Which one of these compounds belongs to the same homologous series as methane?

Draw a circle around the correct answer.

butane                    methanoic acid                    methanol              propene

7c1 mark

The structure of a monomer used to make a polymer is shown.

q5f-0620_s19_qp_32

What structural feature of this molecule shows that it is unsaturated?

7d2 marks

Describe a test to show that this compound is unsaturated. test                     .................................................... observations     ....................................................

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1a1 mark

The structures of six organic compounds are shown.

6-compounds-cie-igcse

Give the name of F.

1b2 marks

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

1c3 marks

Separate: Chemistry and Extended Only

Which two compounds are isomers of each other?

Explain why they are isomers.

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

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

1d2 marks

Explain why B is an unsaturated hydrocarbon.

1e3 marks

Extended Only

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

1f2 marks

Extended Only

Compound A forms an addition polymer.

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

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2a6 marks

Separate: Chemistry and Extended Only

A hydrocarbon has the following structural formula.

 

cyclobutane-displayed-black

 

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]

2b3 marks

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]

2c5 marks

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.

 

but-2-ene-exam-q-structure

 

[3]

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

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

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

 [2]

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3a3 marks

Extended Only

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

 

alcohol

formula

heat of combustion in kJ / mol

methanol 

CH3OH 

730

ethanol 

CH3–CH2–OH 

1380

propan-1-ol

 

 

butan-1-ol 

CH3–CH2–CH2–CH2–OH

2680

pentan-1-ol 

CH3–CH2–CH2–CH2–CH2–OH

3350

 

i) Complete the table. 

[2]

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

 

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

 [1]

3b3 marks

Extended Only

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

3c3 marks

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]

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6 marks

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]

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4a3 marks

Extended Only

The alcohols form a homologous series.

Give three characteristics of a homologous series.

4b3 marks

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]

4c3 marks

Separate: Chemistry and Extended Only

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

 

oxidation-of-butanol-equipment

 

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]

4d5 marks

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.

 

rate-graph

 

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]

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5a2 marks

Extended Only

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

Give two general characteristics of a homologous series.

5b4 marks

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]

5c3 marks

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]

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6a7 marks

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]

6b5 marks

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]

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7a2 marks

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.

7b6 marks

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.

 

petrol-pump

 

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]

7c2 marks

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.

7d3 marks

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.

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8a2 marks

Extended Only

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

Give two general characteristics of a homologous series.

8b5 marks

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]

8c3 marks

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]

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9a2 marks

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

formula

straight C subscript 2 straight H subscript 2

straight C subscript 3 straight H subscript 4

 

structure

straight H minus straight C identical to straight C minus CH subscript 3

straight H minus straight C identical to straight C minus CH subscript 2 minus CH subscript 3

names

ethyne

 

but-1-yne

9b2 marks

Extended Only

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

Give two other characteristics of members of a homologous series.

9c1 mark

Separate: Chemistry Only

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

9d2 marks

Alkynes are unsaturated.

Describe a test for unsaturation.

test   ........................

result ........................ 

9e2 marks

Separate: Chemistry and Extended Only

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

9f2 marks

Extended Only

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

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10a2 marks

Separate: Chemistry and Extended Only

Propane reacts with chlorine in a photochemical reaction as shown.

straight C subscript 3 straight H subscript 8 space plus Cl space rightwards arrow straight C subscript 3 straight H subscript 7 Cl space plus space HCl

Draw two structural isomers of compounds with the formula C3H7Cl.

Show all of the atoms and all of the bonds.

 

 

 

10b3 marks

There are three functional groups in compound A.

q6c-0620-s20-qp-42

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

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

10c2 marks

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.

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11a1 mark

The structure of compound S is shown.

qp5qASid_q5-0620_s19_qp_33

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

11b1 mark

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

11c1 mark

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

straight C subscript 2 straight H subscript 5 OH space rightwards arrow space straight C subscript 2 straight H subscript 4 space plus straight X

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

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12a1 mark

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

q5-0620_s19_qp_41

What is the general formula of alkenes?

12b2 marks

Extended Only

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

q5f-0620_s19_qp_41

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

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13a1 mark

The structure of myrcene is shown.

q7_0620-s20-qp-31_cie-igcse-chemistry

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

13b3 marks

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

13c1 mark

Butane is a saturated hydrocarbon.

To which homologous series does butane belong?

Draw a circle around the correct answer.

alcohol                    alkane                   alkene                   carboxylic acid

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1a3 marks

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]

1b
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4 marks

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]

1c4 marks

Extended Only

An ester has the molecular formula C3H6O2.

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

Name of ester

 

 

Structural formula

 

 

1d1 mark

Separate: Chemistry and Extended Only

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

1e4 marks

Separate: Chemistry and Extended Only

A polyester is represented by the structure shown.

polyester-structure

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.

polyester-monomers

[2]

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2a5 marks

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]

2b3 marks

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]

2c3 marks

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]

2d7 marks

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.

 

experiment

acid

concentration in mol / dm3 

temperature / oC

time / minutes

A

propanoic

1.0

20

5

B

propanoic

1.0

30

3

C

propanoic

0.5

20

8

D

hydrochloric

1.0

20

1

 

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]

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3a
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4 marks

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

CH3–OH
methanol

CH3–CH2–CH2–CH2–OH butanol

i) Give two general characteristics of a homologous series.

 [2]

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

 [2]

3b2 marks

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

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

 [1]

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

 [1]

3c4 marks

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]

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4a9 marks

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]

4b3 marks

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]

4c2 marks

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]

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5a2 marks

Butane is an alkane. It has the following structural formula

Butane Displayed 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

5b5 marks

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]

5c5 marks

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]

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6a2 marks

The table shows some information about aldehydes.

Complete the table.

name

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

ethanal

propanal

butanal

molecular formula

CH2O

C2H4O

C3H6O

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

6b1 mark

Deduce the general formula of aldehydes.

6c1 mark

The structural formula of ethanal is shown.

Zm7YJV~p_q5e_0620-s20-qp-41_cie-igcse-chemistry

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?

6d1 mark

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?

6e2 marks

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

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