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

The structures of six organic compounds are shown.

Give the name of F.

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

Give the general formula of this homologous series.

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

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

Which two compounds are isomers of each other?

Explain why they are isomers.

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

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

Explain why B is an unsaturated hydrocarbon.

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

Compound A forms an addition polymer.

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

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]

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]

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]

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

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]

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]

The alcohols form a homologous series.

Give three characteristics of a homologous series.

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]

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]

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]

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]

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

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

Give two other characteristics of members of a homologous series.

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 ........................ 

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

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

Propane reacts with chlorine in a photochemical reaction as shown.

$C_3{H}_8+C{l}_2\to C_3{H}_{7}Cl+HCl$

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

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.

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\to {\mathrm{C}}_2{\mathrm{H}}_4+\mathrm{X}$

Draw the structure of a molecule of ethanol. 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

Choose from the following compounds to answer the questions.

Each compound may be used once, more than once or not at all.

State which compound:

i) has a molecule with only 14 atoms

[1]

ii) can be oxidised to form propanoic acid

[1]

iii) is an isomer of butane

[1]

iv) reacts with steam to make an alcohol

[1]

v) can be polymerised to make a polyester.

[1]

State which two compounds in aqueous solution turn blue litmus red.

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]

An ester has the molecular formula C₃H₆O₂.

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

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

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]

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 products formed when pentan-1-ol reacts with an excess of oxygen.

[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)

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.

Three compounds, P, Q and R, are members of the same homologous series.

Their molecular formulae are shown in the table.

The structural formula of P is CH₃COOH.

Identify the functional group present in P.

Deduce the general formula of this homologous series.

R is not the last member of this homologous series.

Deduce the molecular formula of the member of this series that comes immediately after R.

Draw the displayed formula of Q.

Show all of the atoms and all of the bonds.

State what is meant by the term structural isomers.

C₄H₁₀ has two structural isomers.

Give the structural formula of each of these two isomers.

The structural formula of compound X is CH₃CH₂OH.

Give the molecular formula of X.

Draw the displayed formula of X.

Show all of the atoms and all of the bonds.

The structural formula of compound Y is CH₂=CH₂.

State why Y is an unsaturated compound.

A molecule of X and a molecule of Y each contain two carbon atoms.

State why X and Y are not members of the same homologous series.

State why a displayed formula gives more information about a molecule than a molecular formula does.