Organic Families (Cambridge (CIE) IGCSE Chemistry)

Exam Questions

9 hours62 questions
1a2 marks

The alkanes are a family of saturated hydrocarbons. Their reactions include combustion, cracking and substitution.

 i) What is meant by the term hydrocarbon?

 [1]

 ii) What is meant by the term saturated?

 [1]

1b3 marks

i) What is the general formula for the homologous series of alkanes?

 [1]

 ii) Calculate the mass of one mole of an alkane with 14 carbon atoms.

 [2]

1c4 marks

Cracking is used to obtain short-chain alkanes, alkenes and hydrogen from long-chain alkanes.

 i) Give a use for each of the three products listed above.

 short-chain alkanes ..................................................

 alkenes ..................................................

 hydrogen ..................................................

 [3]

 ii) Write an equation for the cracking of decane, C10H22, which produces two different alkenes and hydrogen as the only products.

 [1]

1d2 marks

Separate: Chemistry and Extended Only

Chlorine reacts with propane in a substitution reaction to form 1-chloropropane.

 CH3–CH2–CH3 + Cl2 → CH3–CH2–CH2–Cl + HCl

 

i) What is the essential condition for the above reaction?

 [1]

 ii) There is more than one possible substitution reaction between chlorine and propane.

 Suggest the structural formula of a different product.

 [1]

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2a
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4 marks

Separate: Chemistry and Extended Only

A compound X contains 82.76% of carbon by mass and 17.24% of hydrogen by mass.

i) Calculate the empirical formula of compound X.

[2]

ii) Compound X has a relative molecular mass of 58.

Deduce the molecular formula of compound X.

[2]

2b2 marks

Separate: Chemistry Only

Alkenes are unsaturated hydrocarbons.

i) State the general formula of alkenes.

[1]

ii) State the empirical formula of alkenes.

[1]

2c2 marks

What is meant by the term unsaturated hydrocarbon?

unsaturated

hydrocarbon 

2d3 marks

Describe a test that would distinguish between saturated and unsaturated hydrocarbons.

Reagent: 

Observation (saturated hydrocarbon):

Observation (unsaturated hydrocarbon):

2e4 marks

Extended Only

Addition polymers can be made from alkenes. The diagram shows part of an addition polymer.

polymer-polybutene

i) Draw a circle on the diagram to show one repeat unit in this polymer.

[1]

ii) Give the structure and the name of the monomer used to make this polymer.

[2]

iii) Give the structure of an isomer of the alkene in (e)(ii).

[1]

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3a4 marks

Natural gas, which is mainly methane, is a fossil fuel.

 i) What is meant by the term fuel?

 [1]

 ii) Name two other fossil fuels.

 [2] 

iii) Name a solid fuel which is not a fossil fuel.

 [1]

3b4 marks

Fossil fuels are formed by the anaerobic decomposition of organic matter. Anaerobic means in the absence of oxygen.

 i) The organic matter contains hydrogen and carbon. Suggest the products that would be formed if the decomposition occurred in the presence of oxygen.

 [2]

 ii) What are the two main disadvantages in the widespread use of fossil fuels?

 [2]

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4a7 marks

Separate: Chemistry and Extended Only

Esters, polyesters and fats all contain the ester linkage.

Esters can be made from alcohols and carboxylic acids. For example, the ester ethyl ethanoate can be made by the following reaction.

CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O

i) Name the carboxylic acid and the alcohol from which the following ester could be made.

ethyl-ethanoate

[2]

ii) 6.0 g of ethanoic acid, M= 60, was reacted with 5.5 g of ethanol, Mr = 46.  Determine which is the limiting reagent and the maximum yield of ethyl ethanoate, Mr = 88.

Number of moles of ethanoic acid =

[1]

Number of moles of ethanol =

[1]

The limiting reagent is

[1]

Number of moles of ethyl ethanoate formed =

[1]

Maximum yield of ethyl ethanoate =

[1]

4b3 marks

Separate: Chemistry and Extended Only

The following two monomers can form a polyester.

diol-and-dioic-acid

       Draw the structural formula of this polyester. Include two ester linkages.

4c5 marks

Fats and vegetable oils are esters. The formulae of two examples of natural esters are given below.

natural-esters

i) One ester is saturated, the other is unsaturated. Describe a test to distinguish between them. Test: Result with unsaturated ester: Result with saturated ester:

[3]

ii) Deduce which one of the above esters is unsaturated. Give a reason for your choice.

[2]

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5a2 marks

A major source of energy is the combustion of fossil fuels.

i) Name a solid fossil fuel.

 [1]

 ii) Name a gaseous fossil fuel.

 [1]

5b5 marks

Petroleum is separated into more useful fractions by fractional distillation.

 i) Name two liquid fuels obtained from petroleum.

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

[2]

 ii) Name two other useful products obtained from petroleum that are not used as fuels.

 

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

 

[2]

 iii) Give another mixture of liquids that is separated on an industrial scale by fractional distillation.

 [1]

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6a1 mark

Large hydrocarbons can be cracked to form smaller hydrocarbons. Complete the chemical equation for cracking tridecane, C13H28, to form an alkene and one other hydrocarbon.

C13H28 → C3H6 + ..............

6b1 mark

Separate: Chemistry and Extended Only

Ethene is an alkene.

Draw the structure of ethene showing all of the atoms and all of the bonds.

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7a1 mark

The properties of five alkenes at room temperature are shown in the table.

alkene

number of carbon atoms in a molecule

state at room temperature

density in g / cm3

boiling point / °C

ethene

2

gas

0.0012

–104

propene

3

gas

0.0018

–47

butene

4

gas

0.0024

 

pentene

5

liquid

0.64

30

hexene

6

liquid

0.67

63

Answer these questions using only the information in the table.

Describe the general trend in the density of the alkenes.

 

7b1 mark

Predict the boiling point of butene.

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8a5 marks

Islay is an island off the west coast of Scotland. The main industry on the island is making ethanol from barley.

Barley contains the complex carbohydrate, starch. Enzymes catalyse the hydrolysis of starch to a solution of glucose.

Yeast cells are added to the aqueous glucose. Fermentation produces a solution containing up to 10% of ethanol.

 i) Complete the word equation for the fermentation of glucose.

 glucose → .......................... + ..........................

 [1]

 ii) Explain why is it necessary to add yeast and suggest why the amount of yeast in the mixture increases.

 [2]

 iii) Fermentation is carried out at 35°C. For many reactions a higher temperature would give a faster reaction. Why is a higher temperature not used in this process?

 [2]

8b3 marks

The organic waste, the residue of the barley and yeast, is disposed of through a pipeline into the sea. In the future this waste will be converted into biogas by the anaerobic respiration of bacteria. Biogas, which is mainly methane, will supply most of the island’s energy.

 

i) Anaerobic means in the absence of oxygen. Suggest an explanation why oxygen must be absent.

 [1]

 ii) The obvious advantage of converting the waste into methane is economic.

 Suggest two other advantages.

 [2]

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1a4 marks

Propane reacts with chlorine to form a mixture of chloropropanes. This is a photochemical reaction.

i) What is meant by the phrase photochemical reaction?

[1]

ii) The products of this reaction include two isomers, one of which has the following structural formula.

1-chloropropane

   Draw the structural formula of the other isomer.

[1]

iii) Explain why these two different compounds are isomers.

[2]

1b
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3 marks

Bond breaking is an endothermic change and bond forming is an exothermic change.  Bond energy is the amount of energy in kJ / mol needed to break one mole of the specified bond.

propane--cl2

Use the following bond energies to determine whether this reaction is exothermic or endothermic. You must show your reasoning.

Bond

Bond energies in kJ / mol

C-Cl

338

C-H

412

Cl-Cl

242

H-Cl

431

C-C

348

1c5 marks

i) Chloropropane can be hydrolysed to propanol, CH3CH2CH2OH, by sodium hydroxide. Write the equation for this reaction.

[2]

ii) Propanol can be dehydrated. It loses a water molecule to form a hydrocarbon.

Give the name and structural formula of this hydrocarbon.

[2]

iii) Propanol is oxidised to a carboxylic acid by acidified potassium manganate(VII).

Deduce the name of this acid.

[1]

1d
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5 marks

Propanol reacts with methanoic acid to form the ester propyl methanoate.

CH3CH2CH2OH + HCOOH → HCOOCH2CH2CH3 + H2O

4.0 g of methanoic acid was reacted with 6.0 g of propanol.

i) Calculate the Mr of methanoic acid.

[1]

ii) Calculate the Mof propanol.

[1]

iii) Determine which one is the limiting reagent. Show your reasoning.

[2]

iv) Calculate the maximum yield in grams of propyl methanoate, Mr = 88.

[1]

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2 marks

The alkenes are a series of unsaturated hydrocarbons. They have the general molecular formula CnH2n.

Deduce the molecular formula of an alkene which has a relative molecular mass of 126.

Show your working.

2b
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8 marks

The structural formula of propene is drawn below.  

propene

 

i) Draw a diagram showing the arrangement of the valency electrons in one molecule of this covalent compound.

 Use x to represent an electron from an atom of carbon.

Use o to represent an electron from an atom of hydrogen.

 [3]

 ii) Draw the structure of the polymer formed from propene

 [2]

 iii) Bond energy is the amount of energy, in kJ, which must be supplied to break one mole of the bond. 

bond

bond energies in kJ / mol

H-H

+436

C=C

+610

C-C

+346

C-H

+415

 Use the data in the table to show that the following reaction is exothermic.

 

cie-igcse-hydrogenation-of-propene

 

[3]

2c4 marks

This question is concerned with some of the addition reactions of but-1-ene.

 i) Name the product formed when but-1-ene reacts with water.

 [1]

 ii) Complete the equation.

 CH3–CH2–CH=CH2 + Br2 → .....................................................................

 [2]

 iii) Deduce the formula of the compound which reacts with but-1-ene to form 1-iodobutane.

 [1] 

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3a
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6 marks

The alcohols form a homologous series.

i) Give three characteristics which all members of a homologous series share.

[3]

ii) Give the name of the third member of this series.

[1]

iii) Deduce the molecular formula of the alcohol whose Mr = 158. Show your working.

[2]

3b2 marks

Explain why the following two alcohols are isomers.

alcohol-isomers
3c5 marks

This question is based on typical reactions of butan-1-ol.

i) When butan-1-ol, CH3–CH2–CH2–CH2–OH, is passed over the catalyst silicon(IV) oxide, water is lost. Deduce the name and the structural formula of the organic product in this reaction.

[2]

ii) Suggest the name of the ester formed from butanol and ethanoic acid.

[1]

iii) Butan-1-ol is oxidised by acidified potassium manganate(VII).

Deduce the name and the structural formula of the organic product in this reaction.

[2]

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4a2 marks

Alcohols can be made by fermentation or from petroleum.

Ethanol can be made by the fermentation of glucose.

C6H12O6 (aq) rightwards arrow with yeast on top2C2H5OH (aq) + 2CO2 (g)       exothermic reaction

Yeast are living single-cell fungi which ferment glucose by anaerobic respiration. This reaction is catalysed by enzymes from the yeast.

i) What are enzymes?

[1]

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

[1]

4b4 marks

The following observations were noted.

  • When a small amount of yeast was added to the aqueous glucose the reaction started and the solution went slightly cloudy.

  • The reaction rate increased and the solution became cloudier and warmer.

  • After a while, the reaction rate decreased and eventually stopped, leaving a 14% solution of ethanol in water.

i) Why did the reaction rate increase?

[1]

ii) Suggest an explanation for the increase in cloudiness of the solution.

[1]

iii) Give two reasons why the fermentation stopped.

[2]

4c2 marks

One use of ethanol is in alcoholic drinks.

Give two other uses of ethanol.

4d5 marks

Alcohols can be made from petroleum by the following sequence of reactions.

alkanes from petroleum → alkene → alcohol

Describe the manufacture of ethanol from hexane, C6H14. Include in your description an equation and type of reaction for each step.

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5a2 marks

The ester linkage showing all the bonds is drawn as

ester-linkage

or more simply it can be written as –COO–.

i) Give the structural formula of the ester ethyl ethanoate.

[1]

ii) Deduce the name of the ester formed from methanoic acid and butanol.

[1]

5b3 marks

Draw the structural formula of the polyester formed from the following monomers.

HOOCC6H4COOH and HOCH2CH2OH

You are advised to use the simpler form of the ester linkage.

5c5 marks

Esters can be used as solvents in chromatography. The following shows a chromatogram of plant acids.

chromatogram-of-plant-acid

An ester was used as the solvent and the chromatogram was sprayed with bromothymol blue.

i) Suggest why it was necessary to spray the chromatogram.

[2]

ii) Explain what is meant by the Rf value of a sample.

[1]

iii) Calculate the Rf values of the two samples and use the data in the table to identify the plant acids.

Plant acid

Rf value

tartaric acid

0.22

citric acid

0.30

oxalic acid

0.36

malic acid

0.46

succinic acid

0.60

[2]

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6a6 marks

The alcohols form a homologous series. The first member of this series is methanol, CH3OH.

i) Give the general formula of the alcohols.

[1]

ii) The mass of one mole of an alcohol is 116 g. What is its formula? Show your reasoning.

[2]

ii) Draw a diagram showing the arrangement of the outer (valency) electrons in one molecule of methanol.

Use x to represent an electron from a carbon atom.
Use o to represent an electron from a hydrogen atom.
Use ● to represent an electron from an oxygen atom.

[3]

6b5 marks

Methanol is manufactured using the following method.

CH4 (g) + H2O (g) → CO (g) + 3H2 (g)   reaction 1 CO (g) + 2H2 (g) rightwards harpoon over leftwards harpoon CH3OH (g)    reaction 2

The conditions for reaction 2 are:

pressure

100 atmospheres

catalyst

a mixture of copper, zinc oxide and aluminium oxide

temperature

250°C

The forward reaction is exothermic.

i) Why is high pressure used in reaction 2?

[2]

ii) Explain why using a catalyst at 250 °C is preferred to using a higher temperature of 350°C and no catalyst.

[3]

6c3 marks

Methanol is oxidised by atmospheric oxygen. This reaction is catalysed by platinum.

i) The products of this reaction include a carboxylic acid. Give its name and structural formula.

[2]

ii) Deduce the name of the ester formed by the reaction of methanol with the carboxylic acid named in (i).

[1]

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7a4 marks

Propenoic acid is an unsaturated carboxylic acid. The structural formula of propenoic acid is given below.

propanoic-acid

i) Describe how you could show that propenoic acid is an unsaturated compound. 

Test:

Result:

[2]

ii) Without using an indicator, describe how you could show that a compound is an acid.

Test:

Result:

[2]

7b3 marks

Propenoic acid reacts with ethanol to form an ester. Deduce the name of this ester. Draw its structural formula.

Name of ester:

Structural formula showing all bonds:

7c5 marks

An organic compound has a molecular formula C6H8O4. It is an unsaturated carboxylic acid. One mole of the compound reacts with two moles of sodium hydroxide.

i) Explain the phrase molecular formula.

[2]

ii) One mole of this carboxylic acid reacts with two moles of sodium hydroxide. How many moles of –COOH groups are there in one mole of this compound?

[1]

iii) What is the formula of another functional group in this compound?

[1]

iv) Deduce a structural formula of this compound.

[1]

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8a3 marks

Alkanes and alkenes are both series of hydrocarbons.

i) Explain the term hydrocarbon.

[1]

ii) What is the difference between these two series of hydrocarbons?

[2]

8b1 mark

Alkenes and simpler alkanes are made from long-chain alkanes by cracking.

Complete the following equation for the cracking of the alkane C20H42.

C20H42  → 2C4H8 + 2C2H4 + ...............

8c7 marks

Alkenes such as butene and ethene are more reactive than alkanes.

Alkenes are used in the petrochemical industry to make a range of products, which includes polymers and alcohols.

i) Dibromoethane is used as a pesticide. Complete the equation for its preparation from ethene.

ethene-bromination

[1]

ii) The structural formula of a poly(alkene) is given below.

Deduce the structural formula of its monomer.

polybut-2-ene-q-image

[2]

iii) How is butanol made from butene, CH3 –CH2 –CH=CH2? Include an equation in your answer.

[2]

iv) Cracking changes alkanes into alkenes. How could an alkene be converted into an alkane?

Include an equation in your answer.

[2]

8d4 marks

20 cm3 of a hydrocarbon was burnt in 175 cm3 of oxygen. After cooling, the volume of the remaining gases was

125 cm3. The addition of aqueous sodium hydroxide removed carbon dioxide leaving 25 cm3 of unreacted oxygen.

Volume of oxygen used = .......... cm3

[1]

Volume of carbon dioxide formed = .......... cm3

[1]

Deduce the formula of the hydrocarbon and the balanced equation for the reaction.

[2]

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9a6 marks

The structural formula of a butanol is given below.

CH3—CH2—CH2—CH2—OH

Butanol can be made from petroleum and also by fermentation.

i) Describe the chemistry of making butanol from petroleum by the following route.

petroleum → butene → butanol

[3]

ii) Explain, in general terms, what is meant by fermentation.

[3]

9b2 marks

Butanol can be oxidised to a carboxylic acid by heating with acidified potassium manganate(VII). Give the name and structural formula of the carboxylic acid.

9c4 marks

Butanol reacts with ethanoic acid to form a liquid, X, which has the sweet smell of bananas. Its empirical formula is C3H6O and its Mr is 116.

i) What type of compound is liquid X?

[1]

ii) Give the molecular formula of liquid X.

[1]

iii) Draw the structural formula of X. Show all the individual bonds.

[2]

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10a6 marks

But-1-ene is a typical alkene. It has the structural formula shown below.

CH3–CH2–CH=CH2

The structural formula of cyclobutane is given below.

cyclobutane-displayed-black

These two hydrocarbons are isomers.

 i) Define the term isomer.

 [2]

 ii) Draw the structural formula of another isomer of but-1-ene.

 [1]

 iii) Describe a test which would distinguish between but-1-ene and cyclobutane.

 reagent ..................................................

 result with but-1-ene ..................................................

 result with cyclobutane ..................................................

 [3]

10b2 marks

Describe how alkenes, such as but-1-ene, can be made from alkanes.

10c3 marks

Name the product formed when but-1-ene reacts with:

 bromine, ..........................................................................................................

[1]

 hydrogen, ..........................................................................................................

[1]

 steam. ..........................................................................................................

[1]

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11a3 marks

The alcohols form an homologous series.

Give three characteristics of a homologous series.

11b3 marks

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

 

CH3—CH2—CH2—CH2—OH and (CH3)2CH—CH2OH

i) Explain why they are isomers.

[2]

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

[1]

11c3 marks

Copper(II) oxide can oxidise butan-1-ol to liquid X whose pH is 4.

 

cie-igcse-sq-11-2-practical

i) Name another reagent which can oxidise butan-1-ol.

[1]

ii) What type of compound is liquid X and what is its formula?

[2]

11d6 marks

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.

cie-igcse-sq-11-2-graph

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

[2]

ii) Why does the rate increase initially?

[1]

iii) Suggest two reasons why the rate eventually decreases.

[2]

iv) Why is fermentation carried out in the absence of air?

[1]

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12a3 marks

The alcohols form a homologous series. Two characteristics of a homologous series are that the physical properties of the members vary in a predictable way and they have similar chemical properties.

Complete the table.

name

formula

mass of one mole / g

boiling point / oC

methanol

CH3 –OH

32

64

ethanol

CH3 –CH2 –OH

46

78

propan-1-ol

CH3 –CH2 –CH2 –OH

60

98

butan-1-ol

CH3 –CH2 –CH2 –CH2 –OH

74

118

pentan-1-ol

 

 

138

hexan-1-ol

CH3 –CH2 –CH2 –CH2 –CH2 –CH2 –OH

102

 

12b2 marks

Give two other characteristics of a homologous series.

12c3 marks

Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound methanol.

Use x to represent an electron from a carbon atom.
Use ● to represent an electron from an oxygen atom.
Use o to represent an electron from a hydrogen atom.

12d3 marks

Alcohols can be oxidised to carboxylic acids by heating with acidic potassium manganate(VII).

i) Draw the structural formula of the carboxylic acid formed by the oxidation of propan-1-ol. Show all the bonds.

[1]

ii) Describe how ethanol could be oxidised to ethanoic acid by fermentation.

[2]

12e2 marks

Propan-1-ol and ethanoic acid react together to form an ester. Give its name and structural formula.

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13a4 marks

The alkenes are a homologous series of unsaturated hydrocarbons.

The table below gives the names, formulae and boiling points of the first members of the series.

Name

Formula

Boiling point  / oC

 ethene

C2H4

-103.7

 propene

C3H6

-47.6

 butene

C4H8

-6.3

 pentene

C5H10

30

 hexene

 

 

i) Complete the table by giving the formula of hexene and by predicting its boiling point.

[2]

ii) Deduce the formula of the alkene which has a relative molecular mass of 168. Show your working.

[2]

13b3 marks

Describe a test that will distinguish between the two isomers, but-2-ene and cyclobutane.

test ..........................................................................................................

result with but-2-ene  ..........................................................................................................

result with cyclobutane  ..........................................................................................................

13c3 marks

Alkenes undergo addition reactions.

i) What class of organic compound is formed when an alkene reacts with water?

[1]

ii) Draw the structure of the polymer formed from but-2-ene.

[2]

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14a7 marks

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]

14b5 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]

14c2 marks

Hydrocarbons burn in excess oxygen to form carbon dioxide and water. 20 cm3 of a gaseous hydrocarbon burned in an excess of oxygen, 200 cm3. After cooling, the volume of the residual gas at r.t.p. was 150 cm3, 50 cm3 of which was oxygen.

i) Determine the volume of the oxygen used.

[1]

ii) Determine the volume of the carbon dioxide formed.

[1]

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15a3 marks

The fractional distillation of crude oil usually produces large quantities of the heavier fractions. The market demand is for the lighter fractions and for the more reactive alkenes. The heavier fractions are cracked to form smaller alkanes and alkenes as in the following example.

C8H18 → C4H10 +      C4H8

octane butane  butene

i) Write a different equation for the cracking of octane.

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

 [1]

 ii) The cracking of octane can produce isomers with the molecular formula C4H8.

 Draw the structural formulae of two of these isomers.

 [2]

15b4 marks

i) Give the essential condition for the reaction between chlorine and butane.

[1]

ii) What type of reaction is this?

[1]

iii) This reaction produces a mixture of products. Give the names of two products that contain four carbon atoms per molecule.

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

[2]

15c2 marks

Alkenes are more reactive than alkanes and are used to make a range of organic chemicals. Propene, CH3–CH=CH2, is made by cracking. Give the structural formula of the addition product when propene reacts with the following.

 i) water

 [1]

 ii) bromine

 [1]

15d
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4 marks

Propene reacts with hydrogen iodide to form 2-iodopropane.

CH3−CH=CH2 + HI → CH3−CHI−CH3

1.4 g of propene produced 4.05 g of 2-iodopropane.

Calculate the percentage yield.

moles of CH3–CH=CH2 reacted = ..................................................

maximum moles of CH3–CHI–CH3 that could be formed = ..................................................

mass of one mole of CH3–CHI–CH3 = 170 g

maximum mass of 2- iodopropane that could be formed = ..................................................

percentage yield .................................................. %

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16a
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9 marks

The alcohols form a homologous series. The first four members are methanol, ethanol, propan-1-ol and butan-1-ol.

One characteristic of a homologous series is that the physical properties vary in a predictable way. The table below gives the heats of combustion of the first three alcohols.

Alcohol

Formula

Heat of combustion in kJ / mol

methanol

CH3OH

-730

ethanol

CH3-CH2-OH

-1370

propan-1-ol

CH3-CH2-CH2-OH

-2020

butan-1-ol

CH3-CH2-CH2-CH2-OH

 

i) The minus sign indicates that there is less chemical energy in the products than in the reactants. What form of energy is given out by the reaction?

[1]

ii) Is the reaction exothermic or endothermic?

[1]

iii) Complete the equation for the complete combustion of ethanol.

[2]

iv) Determine the heat of combustion of butan-1-ol by plotting the heats of combustion of the first three alcohols against the number of carbon atoms per molecule.

graph-heat-of-combustion

[3]

v) Describe two other characteristics of homologous series.

[2]

16b2 marks

Give the name and structural formula of an isomer of propan-1-ol.

16c6 marks

Methanol is made from carbon monoxide.

CO (g) + 2H2(g)rightwards harpoon over leftwards harpoon CH3OH (g) the forward reaction is exothermic

i) Describe how hydrogen is obtained from alkanes.

[2]

ii) Suggest a method of making carbon monoxide from methane.

[2]

iii) Which condition, high or low pressure, would give the maximum yield of methanol? Give a reason for your choice.

[2]

16d3 marks

For each of the following predict the name of the organic product.

i) reaction between methanol and ethanoic acid

[1]

ii) oxidation of propan-1-ol by potassium dichromate(VI)

[1]

iii) removal of H2O from ethanol (dehydration)

[1]

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17a6 marks

A hydrocarbon has the following structural formula.

hydrocarbon

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]

17b3 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]

17c5 marks

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.

sfVPdcYZ_but-2-ene

[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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18a3 marks

The fractional distillation of crude oil usually produces large quantities of the heavier fractions.

The market demand is for the lighter fractions and for the more reactive alkenes. The heavier fractions are cracked to form smaller alkanes and alkenes as in the following example.

C8H18

→ 

 C4H10

+

C4H8

octane 

 

 butane 

 

butene

 i) Write a different equation for the cracking of octane.

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

[1]

ii) The cracking of octane can produce isomers with the molecular formula C4H8. Draw the structural formulae of two of these isomers.

[2]

18b4 marks

i) Give the essential condition for the reaction between chlorine and butane.

[1]

ii) What type of reaction is this?

[1]

iii) This reaction produces a mixture of products. Give the names of two products that contain four carbon atoms per molecule.

[2]

18c2 marks

Alkenes are more reactive than alkanes and are used to make a range of organic chemicals. Propene, CH3–CH=CH2, is made by cracking. Give the structural formula of the addition product when propene reacts with the following.

 i) water

[1]

 ii) bromine

[1]

18d
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4 marks

Propene reacts with hydrogen iodide to form 2-iodopropane.

CH3−CH=CH2 + HI →  CH3−CHI−CH3

1.4 g of propene produced 4.0 g of 2-iodopropane. Calculate the percentage yield.

moles of CH3–CH=CH2 reacted = .........................................

maximum moles of CH3–CHI–CH3 that could be formed = .........................................

mass of one mole of CH3–CHI–CH3 = 170 g

maximum mass of 2- iodopropane that could be formed = .........................................

percentage yield ......................................... %

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1a3 marks

The alkenes are unsaturated hydrocarbons. They form a homologous series, the members of which have the same chemical properties.

They undergo addition reactions and are easily oxidised.

The following hydrocarbons are isomers.

hydrocarbon-isomers

i) Explain why these two hydrocarbons are isomers.

[2]

ii) Give the structural formula of another hydrocarbon which is isomeric with the above.

[1]

1b6 marks

Give the structural formula and name of each of the products of the following addition reactions.

i) ethene and bromine structural formula of product

name of product ................................................................................................... 

[2]

ii) propene and hydrogen structural formula of product

name of product ................................................................................................... 

[2]

iii) but-1-ene and water structural formula of product

name of product ................................................................................................... 

[2]

1c4 marks

Alkenes can be oxidised to carboxylic acids.

i) For example, propene, CH3 –CH=CH2, would produce ethanoic acid, CH3 –COOH, and methanoic acid, H–COOH.

Deduce the formulae of the alkenes which would form the following carboxylic acids when oxidised.

ethanoic acid and propanoic acid

only ethanoic acid

[2]

 ii) escribe the colour change you would observe when an alkene is oxidised with acidified potassium manganate(VII).

[2]

1d2 marks

Alkenes polymerise to form addition polymers.

Draw the structural formula of poly(cyanoethene), include at least two monomer units.

The structural formula of the monomer, cyanoethene, is given below.

polycyanoethane

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2a2 marks

The alkenes are unsaturated hydrocarbons. They form a homologous series, the members of which have similar chemical properties

  •  easily oxidised    

  • addition reactions    

  • polymerisation    

  • combustion.

All the alkenes have the same empirical formula.

i) State their empirical formula.

[1]

ii) Why is the empirical formula the same for all alkenes?

[1]

2b3 marks

Alkenes can be oxidised to carboxylic acids by boiling with aqueous potassium manganate(VII).

i) Pent-2-ene, CH3–CH2–CH=CH–CH3, oxidises to CH3–CH2–COOH and CH3COOH.

Name these two acids.

CH3–CH2–COOH .......................................................................................................

CH3COOH ..........................................................................................................

[2]

ii) Most alkenes oxidise to two carboxylic acids. Deduce the formula of an alkene which forms only one carboxylic acid.

[1]

2c2 marks

Complete the following equations for the addition reactions of propene.

CH3–CH=CH2 + Br2 → .................................... 

CH3–CH=CH2 + H2O → ....................................

2d2 marks

Draw the structural formula of poly(propene).

2e4 marks

0.01 moles of an alkene needed 2.4 g of oxygen for complete combustion. 2.2 g of carbon dioxide were formed.

Determine the following mole ratio.

moles of alkene : moles of O2 : moles of CO2

From this ratio determine the formula of the alkene.

[3]

Write an equation for the complete combustion of this alkene.

[1]

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3a5 marks

Many organic compounds which contain a halogen have chloro, bromo or iodo in their name.

The following diagram shows the structure of 1-chloropropane.

cie-igcse-sq-11-3-1-chloropropane-3a

i) Draw the structure of an isomer of this compound.

[1]

ii) Describe how 1-chloropropane could be made from propane.

[2]

iii) Suggest an explanation why the method you have described in (ii) does not produce a pure sample of 1-chloropropane.

[2]

3b3 marks

Organic halides react with water to form an alcohol and a halide ion.

CH3–CH2–I + H2O → CH3–CH2–OH + I

i) Describe how you could show that the reaction mixture contained an iodide ion.

[2]

ii) Name the alcohol formed when 1-chloropropane reacts with water.

[1]

3c7 marks

The speed (rate) of reaction between an organic halide and water can be measured by the following method.

A mixture of 10 cm3 of aqueous silver nitrate and 10 cm3 of ethanol is warmed to 60 °C.

Drops of the organic halide are added and the time taken for a precipitate to form is measured.

Silver ions react with the halide ions to form a precipitate of the silver halide.

Ag+ (aq) + X- (aq) → AgX (s)

Typical results for four experiments, A, B, C and D, are given in the table.

experiment

organic halide

number of drops

time/min

A

bromobutane

4

6

B

bromobutane

8

3

C

chlorobutane

4

80

D

iodobutane

4

0.1

i) Explain why it takes longer to produce a precipitate in experiment A than in B.

[2]

ii) How does the order of reactivity of the organic halides compare with the order of reactivity of the halogens?

[2]

iii) Explain why the time taken to produce a precipitate would increase if the experiments were repeated at 50 °C.

[3]

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4a2 marks

Petroleum is a source of many important chemicals.

Name two industrial processes which must take place to produce alkenes from petroleum.

4b4 marks

Ethene, CH2=CH2, and propene, CH2=CHCH3, can both be converted into polymers.

 i) What type of polymerisation takes place when ethene forms a polymer?

[1]

ii) What is the empirical formula of the polymer formed from ethene?

[1]

iii) Propene has the structural formula CH2=CHCH3.

Draw two repeat units of the polymer made from propene.

[2]

4c2 marks

Ethene will react with steam to form ethanol.

Propene will react with steam to form two isomers, both of which are alcohols.

Suggest the structures of these alcohols.

4d5 marks

Esters are organic chemicals noted for their characteristic smells. Ethanoic acid and methanol will react to form an ester.

i) Name the catalyst needed to form an ester from ethanoic acid and methanol.

[1]

ii) Name the ester formed when ethanoic acid reacts with methanol.

[1]

iii) Draw the structure of the ester formed when ethanoic acid reacts with methanol. Show all bonds.

[2]

iv) Give the name of a polyester.

[1]

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5a5 marks

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

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

 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]

5b3 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]

5c3 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]

5d7 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 temperatur

cie-igcse-sq-11-2-table

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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6a4 marks

Plants can make complex molecules from simple starting materials, such as water, carbon dioxide and nitrates. Substances produced by plants include sugars, more complex carbohydrates, esters, proteins, vegetable oils and fats.

i) Describe how you could decide from its molecular formula whether a compound is a carbohydrate.

 [2]

 ii) Plants can change the sugar, glucose, into starch which is a more complex carbohydrate. What type of reaction is this?

 [2]

6b5 marks

The fermentation of glucose can be carried out in the apparatus shown below. After a few days the reaction stops. A 12% aqueous solution of ethanol has been produced.

fermentation-of-glucose

 i) The enzyme, zymase, catalyses the anaerobic respiration of the yeast.

 Explain the term respiration.

 [2]

 ii) Complete the equation.

C6H12O6

......................... +

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

glucose

 

     carbon dioxide

 [2]

 iii) Why must air be kept out of the flask?

 [1]

6c2 marks

The ester methyl butanoate is found in apples. It can be made from butanoic acid and methanol. Their structural formulae are given below.

butanoic-acid
methanol

butanoic acid 

methanol

 Use the information given above to deduce the structural formula of methyl butanoate showing all the bonds.

6d3 marks

Proteins are natural macromolecules. Draw the structural formula of a typical protein. Include three monomer units. You may represent amino acids by formulae of the type drawn below.

amino-acid-representations

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7a6 marks

Methanol can be made from a mixture of carbon monoxide and hydrogen.

CO (g) + 2H2 (g) rightwards harpoon over leftwards harpoon CH3OH (g)

The forward reaction is exothermic.

i) Explain why the concentration of methanol at equilibrium does not change.

[2]

ii) Suggest conditions, in terms of temperature and pressure, which would give a high yield of methanol.

[2]

iii) How would the conditions used in practice compare with those given in (ii)? Give an explanation of any differences.

[2]

7b4 marks

Petroleum-based diesel is a mixture of hydrocarbons, such as octane and octene.

i) ‘Oct’ means eight carbon atoms per molecule. Draw a structural formula of an octene molecule.

[1]

ii) Describe a test which would distinguish between octane and octene. Test: Result with octane: Result with octene:

[3]

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8a2 marks

Structural formulae are an essential part of Organic Chemistry.

Draw the structural formula of each of the following. Show all the bonds in the structure.

i) ethanoic acid

[1]

ii) ethanol

[1]

8b6 marks

Ethanoic acid and ethanol react to form an ester.

i) What is the name of this ester?

[1]

ii) The same linkage is found in polyesters. Draw the structure of the polyester which can be formed from the monomers shown below.

HOOC—C6H4—COOH and HO—CH2—CH2—OH

[3]

iii) Describe the pollution problems caused by non-biodegradable polymers.

[2]

8c2 marks

Two macromolecules have the same amide linkage. Nylon, a synthetic polymer, has the following structure.

nylon

Protein, a natural macromolecule, has the following structure.

protein

How are they different?

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9a5 marks

Carboxylic acids contain the group

-cooh

Ethanoic acid is a typical carboxylic acid. It forms ethanoates.

i) Complete the following equations.

Mg + ......CH3COOH → ............................... + ...............................

[2]

sodium hydroxide + ethanoic acid → ........................  ........................ + ........................

[1]

ii) Ethanoic acid reacts with ethanol to form an ester. Give the name of the ester and draw its structural formula. Show all of the bonds.

[2]

9b
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8 marks

Maleic acid is an unsaturated acid. 5.8 g of this acid contained 2.4 g of carbon, 0.2 g of hydrogen and 3.2 g of oxygen.

i) How do you know that the acid contained only carbon, hydrogen and oxygen?

[1]

ii) Calculate the empirical formula of maleic acid.

Number of moles of carbon atoms = ................................

Number of moles of hydrogen atoms = ................................

Number of moles of oxygen atoms = ................................

The empirical formula is .................................................

[3]

iii) The mass of one mole of maleic acid is 116 g. What is its molecular formula?

[2]

iv) Maleic acid is dibasic. One mole of acid produces two moles of H+. Deduce its structural formula.

[2]

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10a4 marks

Alkenes are unsaturated hydrocarbons. They undergo addition reactions.

Two of the methods of making alkenes are cracking and the thermal decomposition of chloroalkanes.

i) Complete an equation for the cracking of the alkane, decane.

C10H22

 →

 .....................

+

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

decane

 

 

 

 

[2]

ii) Propene can be made by the thermal decomposition of chloropropane.

Describe how chloropropane can be made from propane.

reagents:  propane and ..............................

conditions ...................................................

[2]

10b4 marks

The following alkenes are isomers.

alkene-isomers

i) Explain why they are isomers.

[2]

ii) Give the name and structural formula of another hydrocarbon that is isomeric with the above.

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

structural formula

[2]

10c3 marks

Give the name of the product when but-1-ene reacts with each of the following.

steam .........................................................
hydrogen ....................................................
bromine ......................................................

10d7 marks

Alkenes can polymerise.

i) Deduce the name and structural formula of the monomer from the structure of the polymer.

polypropene-repeat-unit

 name of monomer .......................................................     structural formula

[2]

ii) Draw the structure of the polymer formed from the following monomer.

unknown-monomer

[2]

iii) Describe the pollution problems caused by the disposal of polymers in landfill sites and by burning.

landfill sites ..........................................................................................................

[2]

burning ..........................................................................................................

[1]

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11a5 marks

Butan-1-ol is used as a solvent for paints and varnishes, to make esters and as a fuel. Butan-1-ol can be manufactured from but-1-ene, which is made from petroleum.

Biobutanol is a fuel of the future. It can be made by the fermentation of almost any form of biomass - grain, straw, leaves etc.

But-1-ene can be obtained from alkanes such as decane, C10H22, by cracking.

i) Give the reaction conditions.

[2]

ii) Complete an equation for the cracking of decane, C10H22, to give but-1-ene.

C10H22

[2]

iii) Name the reagent that reacts with but-1-ene to form butan-1-ol.

[1]

11b4 marks

i) Balance the equation for the complete combustion of butan-1-ol.

...... C4H9OH + ...... O2 → ...... CO2 + ...... H2O

[2]

ii) Write a word equation for the preparation of the ester butyl methanoate.

[2]

11c3 marks

The fermentation of biomass by bacteria produces a mixture of products which include biobutanol, propanol, hydrogen and propanoic acid.

i) Draw the structural formula of propanol and of propanoic acid. Show all the bonds.

[2]

ii) Why is it important to develop these fuels, such as biobutanol, as alternatives to petroleum?

[1]

11d1 mark

How could you show that butanol made from petroleum and biobutanol are the same chemical?

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12a
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4 marks

The alkanes are generally unreactive. Their reactions include combustion, substitution and cracking.

The complete combustion of an alkane gives carbon dioxide and water.

 i) 10 cm3 of butane is mixed with 100 cm3 of oxygen, which is an excess. The mixture is ignited. What is the volume of unreacted oxygen left and what is the volume of carbon dioxide formed?

 C4H10 (g) + 6.5O2 (g) → 4CO2 (g) + 5H2O (l)

 Volume of oxygen left = .................................................. cm3

 Volume of carbon dioxide formed = ................................. cm3

 [2]

ii) Why is the incomplete combustion of any alkane dangerous, particularly in an enclosed space?

 [2]

12b3 marks

The equation for a substitution reaction of butane is given below.

 CH3−CH2−CH2−CH3 + Cl2 → CH3−CH2−CH2−CH2−Cl + HCl

i) Name the organic product.

[1]

ii) This reaction does not need increased temperature or pressure.

 What is the essential reaction condition?

[1]

 iii) Write a different equation for a substitution reaction between butane and chlorine.

[1]

12c5 marks

Alkenes are more reactive and industrially more useful than alkanes.

They are made by cracking alkanes.

C7H16

CH3−CH=CH2

CH3−CH2−CH=CH2 + H2

heptane

propene

but−1−ene

i) Draw the structural formula of the polymer poly(propene).

 [2]

 ii) Give the structural formula and name of the alcohol formed when but-1-ene reacts with steam.

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

 [1]

 structural formula

 [1]

 iii) Deduce the structural formula of the product formed when propene reacts with hydrogen chloride.

 [1]

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13a4 marks

Esters, fats and polyesters all contain the ester linkage.

The structural formula of an ester is given below.

I4iZm0aV_butyl-ethanoate

Name two chemicals that could be used to make this ester and draw their structural formulae. Show all bonds.

 names ................................ and ..............................

[2]

   structural formulae

[2]

13b3 marks

i) Draw the structural formula of a polyester such as Terylene.

[2]

ii) Suggest a use for this polymer.

[1]

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