Organic chemistry
Exam-style questions with answers for 4.7 Organic chemistry in AQA GCSE Chemistry (spec 8462). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.
All questions and answers
Question 1 · Spec 4.7.1.1 · Crude oil
What is crude oil? [2 marks]
Answer:A finite resource found in rocks (1); formed from the remains of ancient biomass, mainly plankton, buried in mud (1).Question 2 · Spec 4.7.1.1 · Hydrocarbons
What is a hydrocarbon? [1 mark]
Answer:A compound made of hydrogen and carbon atoms only.Question 3 · Spec 4.7.1.1 · Alkanes
State the general formula of the alkanes. [1 mark]
Answer:CₙH₂ₙ₊₂.Question 4 · Spec 4.7.1.1 · Alkanes
Name the first four alkanes. [2 marks]
Answer:Methane and ethane (1); propane and butane (1).Question 5 · Spec 4.7.1.1 · Alkanes
Write the formula of propane. [1 mark]
Answer:C₃H₈.Question 6 · Spec 4.7.1.1 · Alkanes
Why are alkanes described as saturated? [1 mark]
Answer:They contain only single carbon–carbon bonds.Question 7 · Spec 4.7.1.2 · Fractional distillation
Describe how crude oil is separated by fractional distillation. [3 marks]
Answer:Crude oil is heated until it evaporates and enters the column (1); the column is hot at the bottom and cooler at the top (1); fractions condense at different heights according to their boiling points (1).Question 8 · Spec 4.7.1.2 · Fractions
Name three fuels produced from crude oil. [3 marks]
Answer:Any three from: petrol (1); diesel oil (1); kerosene (1); heavy fuel oil (1); liquefied petroleum gases (1).Question 9 · Spec 4.7.1.2 · Petrochemicals
State two useful materials made by the petrochemical industry. [2 marks]
Answer:Any two from: solvents (1); lubricants (1); polymers (1); detergents (1).Question 10 · Spec 4.7.1.3 · Properties
How does chain length affect the properties of hydrocarbons? [3 marks]
Answer:As chain length increases, boiling point increases (1); viscosity increases (1); flammability decreases (1).Question 11 · Spec 4.7.1.3 · Combustion
Write the word equation for the complete combustion of a hydrocarbon. [1 mark]
Answer:Hydrocarbon + oxygen → carbon dioxide + water.Question 12 · Spec 4.7.1.3 · Combustion
Balance the complete combustion of propane: C₃H₈ + O₂ → CO₂ + H₂O. [1 mark]
Answer:C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.Question 13 · Spec 4.7.1.4 · Cracking
What is cracking? [1 mark]
Answer:Breaking down large hydrocarbon molecules into smaller, more useful ones.Question 14 · Spec 4.7.1.4 · Cracking
Name two methods of cracking. [2 marks]
Answer:Catalytic cracking: heat the vapour and pass it over a hot catalyst (1); steam cracking: mix the vapour with steam at a very high temperature (1).Question 15 · Spec 4.7.1.4 · Cracking
Why is cracking important? [2 marks]
Answer:There is high demand for small molecules used as fuels, such as petrol (1); it also makes alkenes used to produce polymers (1).Question 16 · Spec 4.7.1.4 · Cracking
Balance: C₁₀H₂₂ → C₈H₁₈ + ? [1 mark]
Answer:C₂H₄ (ethene).Question 17 · Spec 4.7.1.4 · Alkenes
Describe the test for alkenes. [2 marks]
Answer:Add bromine water (1); it changes from orange to colourless (1).Question 18 · Spec 4.7.2.1 · Alkenes
State the general formula of the alkenes. [1 mark]
Answer:CₙH₂ₙ.Question 19 · Spec 4.7.2.1 · Alkenes
Why are alkenes described as unsaturated? [1 mark]
Answer:They contain a carbon–carbon double bond, so they have two fewer hydrogen atoms than the alkane.Question 20 · Spec 4.7.2.1 · Alkenes
Name the first four alkenes. [2 marks]
Answer:Ethene and propene (1); butene and pentene (1).Question 21 · Spec 4.7.2.2 · Alkenes
What does an alkene form when it reacts with hydrogen? [2 marks]
Answer:An alkane (1); using a catalyst (1).Question 22 · Spec 4.7.2.2 · Alkenes
What forms when ethene reacts with steam? [2 marks]
Answer:Ethanol (1); using a catalyst at high temperature (1).Question 23 · Spec 4.7.2.2 · Combustion
Why do alkenes burn with smoky flames? [1 mark]
Answer:Incomplete combustion produces carbon (soot).Question 24 · Spec 4.7.2.3 · Alcohols
What is the functional group of alcohols? [1 mark]
Answer:–OH.Question 25 · Spec 4.7.2.3 · Alcohols
Name the first four alcohols. [2 marks]
Answer:Methanol and ethanol (1); propanol and butanol (1).Question 26 · Spec 4.7.2.3 · Alcohols
State three reactions of alcohols. [3 marks]
Answer:They burn in air to make carbon dioxide and water (1); react with sodium to make hydrogen (1); are oxidised to carboxylic acids (1).Question 27 · Spec 4.7.2.3 · Fermentation
Describe how ethanol is made by fermentation. [2 marks]
Answer:Yeast is added to sugar solution at about 30–37 °C (1); with no oxygen (anaerobic), producing ethanol and carbon dioxide (1).Question 28 · Spec 4.7.2.3 · Alcohols
State two uses of alcohols. [2 marks]
Answer:Any two from: fuels (1); solvents (1); in alcoholic drinks (ethanol) (1).Question 29 · Spec 4.7.2.4 · Carboxylic acids
What is the functional group of carboxylic acids? [1 mark]
Answer:–COOH.Question 30 · Spec 4.7.2.4 · Carboxylic acids
Name the first four carboxylic acids. [2 marks]
Answer:Methanoic and ethanoic acid (1); propanoic and butanoic acid (1).Question 31 · Spec 4.7.2.4 · Carboxylic acids
What forms when ethanoic acid reacts with sodium carbonate? [2 marks]
Answer:Sodium ethanoate and water (1); and carbon dioxide (1).Question 32 · Spec 4.7.2.4 · Esters
What is made when a carboxylic acid reacts with an alcohol? [2 marks]
Answer:An ester and water (1); using an acid catalyst (1).Question 33 · Spec 4.7.2.4 · Esters
Name the ester formed from ethanol and ethanoic acid. [1 mark]
Answer:Ethyl ethanoate.Question 34 · Spec 4.7.2.4 · Carboxylic acids · Higher only
Explain why carboxylic acids are weak acids. [1 mark]
Answer:They only partially ionise in water.Question 35 · Spec 4.7.3.1 · Addition polymers
What is addition polymerisation? [2 marks]
Answer:Many small alkene molecules (monomers) join together (1); to form very large molecules (polymers), with no other product (1).Question 36 · Spec 4.7.3.1 · Addition polymers
Name the polymer made from ethene. [1 mark]
Answer:Poly(ethene).Question 37 · Spec 4.7.3.1 · Addition polymers
How is a repeating unit drawn from its monomer? [2 marks]
Answer:The C=C double bond becomes a single bond with bonds extending out either side (1); in brackets with n after them (1).Question 38 · Spec 4.7.3.2 · Condensation polymers · Higher only
What is condensation polymerisation? [2 marks]
Answer:Monomers with two functional groups join together (1); losing a small molecule, such as water, each time (1).Question 39 · Spec 4.7.3.2 · Condensation polymers · Higher only
What monomers form a polyester? [1 mark]
Answer:A diol (two –OH groups) and a dicarboxylic acid (two –COOH groups).Question 40 · Spec 4.7.3.2 · Polymers · Higher only
State two differences between addition and condensation polymerisation. [2 marks]
Answer:Any two from: addition uses one type of monomer with a C=C bond, condensation usually uses two types with two functional groups (1); addition gives only the polymer, condensation also gives a small molecule such as water (1).Question 41 · Spec 4.7.3.3 · Amino acids · Higher only
Describe the structure of an amino acid. [1 mark]
Answer:It has two different functional groups: an amine group (–NH₂) and a carboxylic acid group (–COOH).Question 42 · Spec 4.7.3.3 · Amino acids · Higher only
How do amino acids form proteins? [1 mark]
Answer:They react by condensation polymerisation to form polypeptides.Question 43 · Spec 4.7.3.4 · Natural polymers
Name three naturally occurring polymers. [3 marks]
Answer:Any three from: DNA (1); proteins (1); starch (1); cellulose (1).Question 44 · Spec 4.7.3.4 · DNA
Describe the structure of DNA. [2 marks]
Answer:Two polymer chains made from four different monomers called nucleotides (1); in the form of a double helix (1).Question 45 · Spec 4.7.3.4 · Natural polymers
What monomers make up starch and cellulose? [1 mark]
Answer:Sugars (glucose).Question 46 · Spec 4.7.1.1 · Crude oil
Why is crude oil described as finite? [1 mark]
Answer:It is being used up much faster than it forms, so it will run out.Question 47 · Spec 4.7.1.3 · Properties
Why are short-chain hydrocarbons better fuels? [2 marks]
Answer:They are more flammable (1); and less viscous, so they flow easily and ignite easily (1).Question 48 · Spec 4.7.2.3 · Alcohols
Write the formula of ethanol. [1 mark]
Answer:C₂H₅OH.Question 49 · Spec 4.7.3.1 · Addition polymers
Name the monomer used to make poly(propene). [1 mark]
Answer:Propene.Question 50 · Spec 4.7.2.2 · Alkenes
What forms when ethene reacts with bromine? [1 mark]
Answer:Dibromoethane.