Organic Chemistry questions

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Organic Chemistry question collection

Review Organic Chemistry questions for Chemistry, with correct answers shown and coverage across crude oil and fractional distillation; alkanes and alkenes; combustion and cracking.

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Question 1

What do organic compounds always contain?
  1. Carbon
  2. Only oxygen
  3. Only metals
  4. No hydrogen

Question 2

Crude oil is best described as?
  1. A mixture of hydrocarbons
  2. A pure compound of carbon dioxide
  3. A single alkane only
  4. A mixture of metal salts

Question 3

Which atoms are present in a hydrocarbon?
  1. Hydrogen and carbon
  2. Hydrogen and oxygen only
  3. Carbon and oxygen only
  4. Hydrogen, oxygen and nitrogen only

Question 4

Which is an alkane?
  1. Methane (CH4)
  2. Ethene (C2H4)
  3. Water (H2O)
  4. Carbon dioxide (CO2)

Question 5

Which formula is propane?
  1. C3H8
  2. C3H6
  3. C2H6
  4. CH4

Question 6

What is the general formula for alkanes?
  1. CnH2n+2
  2. CnH2n
  3. CnHn
  4. CnH2n-2

Question 7

What are the products of complete combustion of methane?
  1. Carbon dioxide and water
  2. Carbon monoxide and water only
  3. Carbon and hydrogen
  4. Only carbon dioxide

Question 8

Which equation shows complete combustion of methane?
  1. \(\mathrm{CH}_{4} + 2\mathrm{O}_{2} \to \mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O}\)
  2. \(\mathrm{CH}_{4} + \mathrm{O}_{2} \to \mathrm{CO} + \mathrm{H}_{2}\mathrm{O}\)
  3. \(2\mathrm{CH}_{4} + \mathrm{O}_{2} \to 2\mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O}\)
  4. \(\mathrm{CH}_{4} \to \mathrm{C} + 2\mathrm{H}_{2}\)

Question 9

When is incomplete combustion more likely?
  1. Not enough oxygen
  2. Excess oxygen
  3. A catalyst only
  4. Very low pressure only

Question 10

Which harmful gas can form during incomplete combustion?
  1. Carbon monoxide
  2. Oxygen
  3. Nitrogen
  4. Hydrogen

Question 11

Why is carbon monoxide dangerous?
  1. It reduces the blood's ability to carry oxygen
  2. It always explodes in air at room temperature
  3. It turns into pure oxygen in lungs
  4. It is harmless in enclosed spaces

Question 12

How are fractions separated from crude oil?
  1. By fractional distillation
  2. By filtration through paper
  3. By chromatography only
  4. By neutralisation with alkali

Question 13

Fractions are separated in a distillation column mainly because they have different?
  1. Boiling points
  2. Densities only
  3. Colors
  4. Numbers of neutrons

Question 14

In a fractional distillation column, which fractions leave near the bottom?
  1. Fractions with higher boiling points
  2. Fractions with lower boiling points
  3. Only gases
  4. Only the shortest-chain hydrocarbons

Question 15

What does cracking do to long-chain hydrocarbons?
  1. Breaks them into shorter alkanes and alkenes
  2. Combines them into polymers directly
  3. Adds oxygen to form acids only
  4. Removes all carbon atoms

Question 16

An alkene differs from an alkane because an alkene has?
  1. At least one C=C double bond
  2. No carbon atoms
  3. Only single C-C bonds
  4. A metal atom in every molecule

Question 17

Which formula is ethene?
  1. C2H4
  2. C2H6
  3. C3H8
  4. CH4

Question 18

What happens to orange bromine water when added to an alkene?
  1. It is decolorized (turns colorless)
  2. It turns purple
  3. It turns cloudy white only
  4. There is never any color change

Question 19

What is a polymer?
  1. A large molecule made from many repeating monomer units
  2. A mixture of gases from crude oil
  3. A metal with delocalized electrons
  4. A substance made only of ionic bonds

Question 20

Why is burning fossil fuels a concern for climate?
  1. It increases carbon dioxide in the atmosphere
  2. It removes all greenhouse gases
  3. It decreases global temperature in every region
  4. It has no effect on atmospheric composition

Question 21

Crude oil is best described as?
  1. A finite mixture of hydrocarbons
  2. A pure alkane
  3. A renewable biofuel
  4. A compound made only of carbon

Question 22

What is a hydrocarbon?
  1. A compound containing hydrogen and carbon
  2. A compound containing hydrogen and oxygen only
  3. Any compound containing carbon dioxide
  4. Any fuel containing nitrogen

Question 23

What is the general formula for alkanes?
  1. CnH2n+2
  2. CnH2n
  3. CnHn
  4. CnH2n-2

Question 24

Which formula is hexane?
  1. C6H14
  2. C6H12
  3. C6H6
  4. C6H16

Question 25

What type of carbon-carbon bonds are found in a saturated hydrocarbon?
  1. Single carbon-carbon bonds
  2. At least one carbon-carbon double bond
  3. At least one carbon-carbon triple bond
  4. No carbon-hydrogen bonds

Question 26

What are the products of complete combustion of an alkane?
  1. Carbon dioxide and water
  2. Carbon monoxide and hydrogen only
  3. Carbon and oxygen only
  4. Hydrogen and oxygen only

Question 27

When is incomplete combustion more likely?
  1. A limited supply of oxygen
  2. An excess of oxygen
  3. A catalyst only
  4. Low pressure nitrogen only

Question 28

Why is carbon monoxide dangerous?
  1. It binds strongly to haemoglobin, reducing oxygen transport
  2. It makes blood carry more oxygen
  3. It is harmless because it is odorless
  4. It turns instantly into oxygen in lungs

Question 29

How does boiling point usually change as alkane chain length increases?
  1. Increases
  2. Decreases
  3. Stays constant
  4. Alternates up and down regularly

Question 30

Why do longer-chain hydrocarbons have higher boiling points?
  1. They have stronger intermolecular forces between molecules
  2. They have ionic bonds between molecules
  3. Their covalent bonds are easier to break
  4. They contain more oxygen atoms

Question 31

Fractional distillation separates crude oil fractions mainly by differences in what property?
  1. Boiling point
  2. Color
  3. pH
  4. Density only

Question 32

In a fractionating column, low boiling point fractions are collected?
  1. Near the top
  2. Near the bottom
  3. Only in the middle
  4. Outside the column only

Question 33

Why is cracking used in the petrochemical industry?
  1. To convert less useful long-chain hydrocarbons into more useful smaller molecules
  2. To remove all hydrogen from fuels
  3. To increase sulfur content of fuels
  4. To purify oxygen from crude oil

Question 34

What is a key condition needed for cracking?
  1. Vaporised hydrocarbons passed over a hot catalyst
  2. Cold hydrocarbons dissolved in water
  3. High pressure chlorine gas only
  4. Aqueous electrolysis at room temperature

Question 35

What is the general formula of alkenes?
  1. CnH2n
  2. CnH2n+2
  3. CnHn
  4. CnH2n-2

Question 36

What is the test for an alkene?
  1. Orange bromine water is decolorized
  2. Limewater turns milky
  3. A glowing splint relights
  4. Damp red litmus turns blue

Question 37

What product forms when ethene is hydrated?
  1. Ethanol
  2. Ethanoic acid
  3. Methanol
  4. Propane

Question 38

Ethanol can be produced by fermentation using?
  1. Yeast under anaerobic conditions
  2. Oxygen-rich electrolysis only
  3. Catalytic cracking of water
  4. Reaction of methane with chlorine

Question 39

Carboxylic acids in water are generally?
  1. Weak acids
  2. Strong alkalis
  3. Neutral salts
  4. Insoluble bases only

Question 40

Which equation represents complete combustion of ethene?
  1. \(\mathrm{C}_{2}\mathrm{H}_{4} + 3\mathrm{O}_{2} \to 2\mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O}\)
  2. \(\mathrm{C}_{2}\mathrm{H}_{4} + \mathrm{O}_{2} \to 2\mathrm{CO} + 2\mathrm{H}_{2}\)
  3. \(\mathrm{C}_{2}\mathrm{H}_{4} + 2\mathrm{O}_{2} \to 2\mathrm{CO}_{2} + 2\mathrm{H}_{2}\)
  4. \(2\mathrm{C}_{2}\mathrm{H}_{4} + \mathrm{O}_{2} \to 4\mathrm{CO}_{2} + 2\mathrm{H}_{2}\mathrm{O}\)

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Review Organic Chemistry questions for Chemistry, with correct answers shown and coverage across crude oil and fractional distillation; alkanes and alkenes; combustion and cracking.

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