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Which molecular formula and name are correctly paired for an unbranched alkene with one C=C bond?
- C₃H₆ — propene
- C₃H₈ — propene
- C₂H₆ — ethene
- C₂H₄ — propene
What does polyunsaturated mean when describing a food oil molecule?
- It contains more than one carbon-carbon double bond in its hydrocarbon chains.
- It contains many separate water molecules.
- Every carbon-carbon bond is single but the oil contains many molecules.
- It contains one double bond in the entire food sample.
Why is thin poly(ethene) useful as clingfilm but unsuitable for direct contact with a very hot heating element?
- It forms flexible, water-resistant films but softens or melts when heated strongly.
- It is useful only because it is a giant ionic lattice.
- It becomes stronger without limit as temperature rises.
- It reacts explosively with all food at room temperature.
Which name is the alkane with 3 carbon atoms?
- Propane
- Propene
- Propanol
- Propanoic acid
What chemical change helps convert liquid unsaturated vegetable oil into more solid margarine?
- Hydrogen adds across some C=C bonds, decreasing unsaturation and increasing the melting range.
- Oxygen removes every carbon atom from the oil.
- Water hydrolyses all molecules into methane gas.
- Hydrogen creates extra C=C bonds and increases unsaturation.
Which reagent named in the curriculum can oxidise ethanol to ethanoic acid?
- Aqueous sodium chloride
- Acidified potassium manganate(VII)
- Bromine water
- Aqueous silver nitrate
Which statement is most correct about alkanes as fuels?
- They release energy on combustion, so they are useful fuels
- They do not burn in oxygen
- They produce only water when burned
- They are non-flammable
Complete combustion of ethanol produces:
- $\ce{CO}$ and $\ce{H2O}$
- $\ce{CO2}$ and $\ce{H2O}$
- $\ce{C}$ and $\ce{H2}$
- $\ce{CO2}$ only
Ethanoic acid and propanoic acid are successive homologues. What structural difference is expected?
- Propanoic acid has one additional CH₂ unit while retaining the –CO₂H group.
- Propanoic acid replaces –CO₂H with –OH.
- Propanoic acid has one fewer carbon and two fewer hydrogens.
- Their structures must be identical because their chemical properties are similar.
Which pair correctly distinguishes two plastic-recycling routes?
- Mechanical recycling sorts, cleans and remoulds plastic; chemical recycling can crack it into smaller fuel or feedstock molecules.
- Mechanical recycling burns plastic; chemical recycling only washes it.
- Both methods require dumping mixed waste directly into the sea.
- Neither route can recover any useful material or energy resource.
A council considers expanding plastic recycling. Which evaluation includes social, economic and environmental factors?
- Compare public participation and jobs, collection and processing costs, and avoided raw-material use, landfill and emissions.
- Consider only the colour of collection bins.
- Assume recycling has zero cost and zero environmental impact in every system.
- Count landfill space only and ignore people, cost, energy and material recovery.
Which statement about bioethanol is appropriately cautious?
- It is non-renewable because every fuel must come from crude oil
- It is renewable, but farming, processing and transport can add life-cycle emissions
- It is automatically carbon neutral under all production methods
- It cannot release carbon dioxide when burned
What is the general formula for alcohols?
- $\ce{C_nH_{2n}}$
- $\ce{C_nH_{2n+1}OH}$
- $\ce{C_nH_{2n+2}}$
- $\ce{C_nH_{2n+1}COOH}$
Why can careless disposal of non-biodegradable plastic cause long-term pollution?
- It persists, accumulates in habitats and can fragment into smaller pieces without truly biodegrading.
- It disappears immediately because non-biodegradable means water-soluble.
- It always changes completely into harmless oxygen in sunlight.
- It can affect only factories and never ecosystems.
What does saturated mean for an alkane?
- It has no carbon-carbon double or triple bonds and has the maximum hydrogen count for its acyclic carbon skeleton.
- It contains as much liquid hydrocarbon as a container can hold.
- It contains at least one carbon-carbon double bond.
- It cannot contain any hydrogen atoms.
Which statement best describes an alkene?
- A saturated hydrocarbon with only $\ce{C-C}$ single bonds
- An unsaturated hydrocarbon containing at least one $\ce{C=C}$ double bond
- An organic compound containing $\ce{-OH}$
- A mixture of hydrocarbons
Which is the best reason alkenes are used to make polymers?
- They contain a $\ce{C=C}$ bond that can open and link many monomers together
- They are always acidic
- They dissolve in water easily
- They have ionic bonds
Cracking is best described as:
- Separating crude oil into fractions by boiling points
- Breaking long-chain alkanes into shorter alkanes and alkenes using heat and a catalyst
- Adding bromine across a double bond
- A test for unsaturation
Which statement about addition polymers is most correct at O-Level?
- They are formed from monomers containing $\ce{C=C}$ bonds and no small molecule is produced
- They are formed from alcohol and carboxylic acid monomers and always produce water
- They contain ionic bonds
- They are always biodegradable
What happens when propene is shaken with bromine water?
- A squeaky pop is produced
- The bromine water stays orange because propene is saturated
- A white precipitate forms because propene contains chloride ions
- The orange bromine water is decolourised
Why can crude oil be separated by fractional distillation?
- Its hydrocarbons have different boiling ranges
- Each fraction has a different proton number for carbon
- Crude oil is one compound that decomposes into elements
- Its hydrocarbons all boil at exactly the same temperature
Why do boiling points generally rise from ethane to propane to butane within the alkane homologous series?
- Larger molecules have stronger intermolecular attractions, so more energy is needed to separate them.
- Covalent bonds inside each molecule become ionic as the chain length grows.
- Smaller molecules have the strongest intermolecular forces because they move faster.
- Boiling breaks every carbon-carbon bond, so longer chains need fewer bonds broken.
Why can bioethanol made by fermenting plant sugars be described as renewable?
- The plant sugars can be produced again by growing new crops
- Fermentation produces ethanol without any carbon atoms
- The ethanol cannot burn, so it is never used up
- The process turns crude oil back into plants
Which conditions are suitable for fermentation?
- Strong heating to boiling with abundant oxygen
- Ultraviolet light and chlorine gas
- Cold, dry sugar crystals without yeast
- Yeast, aqueous sugar, warm conditions and little or no oxygen
In fermentation, glucose is converted into:
- Ethanol and oxygen
- Ethanol and carbon dioxide
- Ethene and steam
- Ethanoic acid and hydrogen
Which test confirms carbon dioxide produced during fermentation?
- A lighted splint gives a squeaky pop
- Turns limewater milky
- Glowing splint relights
- Damp red litmus turns blue
Bioethanol is commonly produced from glucose by:
- Neutralisation
- Electrolysis
- Fermentation using yeast
- Thermal decomposition
Which products are formed in complete combustion of methane?
- $\ce{CO2}$ and $\ce{H2O}$
- $\ce{CO}$ and $\ce{H2O}$
- $\ce{C}$ and $\ce{H2O}$
- $\ce{CO2}$ and $\ce{H2}$
What condition is needed for alkanes to react with chlorine in a substitution reaction?
- Sunlight/UV light
- Aqueous solution
- High pressure only
- Catalyst $\ce{Fe}$