Question 1:

The correct answer is D. mixture of hydrocarbons.

Crude oil (petroleum) is a naturally occurring, complex mixture of hydrocarbons (alkanes, cycloalkanes, aromatic hydrocarbons, etc.) along with small amounts of other organic compounds containing sulfur, nitrogen, and oxygen.

• A. renewable resource — False; crude oil is a non-renewable fossil fuel.

• B. complex organic compound — False; crude oil is a mixture, not a single compound.

• C. mixture of all organic compounds — False and exaggerated; it contains many, but not all, organic compounds.

• D. mixture of hydrocarbons — Correct, and the most precise description.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 2:

The correct answer is D. ...carbon and hydrogen atoms only.

A hydrocarbon is defined as a compound that contains only carbon and hydrogen atoms.

• A — Adds oxygen → not a hydrocarbon.

• B — Adds oxygen and says "only" → incorrect because oxygen is not allowed in hydrocarbons.

• C — Says "carbon and hydrogen atoms" but does not say "only" — this could allow other elements to be present, so the definition is incomplete.

• D — Correct: contains only carbon and hydrogen atoms.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 3:

The correct answer is B. fractional distillation.

Crude oil is separated into its various components (fractions) based on their different boiling points using fractional distillation in a fractionating column.

• A. filtration — Separates solids from liquids, not used for crude oil separation.

• B. fractional distillation — Correct; used to separate crude oil into fractions like petrol, kerosene, diesel, etc.

• C. cracking — A chemical process that breaks down large hydrocarbon molecules into smaller, more useful ones (done after fractional distillation).

• D. fermentation — A biological process (e.g., sugar → alcohol), unrelated to crude oil separation.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 4:

Most flammable?

→ refinery gases (These have the smallest molecules, lowest boiling points, and are the most volatile and flammable.)

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 5:

Used to surface roads?

→ bitumen (This is the thick, heavy residue left after fractional distillation; used for road surfacing and roofing.)

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 6:

Used as fuel for cars?

→ gasoline (petrol) (This is the main fuel for cars, though diesel is used for some vehicles — petrol is the more common answer for "cars" in general.)

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 7:

The correct answer is A. increases — increases.

As hydrocarbon molecules increase in size (i.e., longer carbon chains and higher molecular mass):

• Boiling point increases — because larger molecules have stronger London dispersion forces (more electrons, more surface area for intermolecular attraction), requiring more energy to overcome.

• Viscosity increases — because larger molecules have greater intermolecular forces and more entanglement, making the liquid flow more slowly.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 8:

The correct answer is C. ...smaller alkanes and alkenes.

In catalytic cracking, long-chain alkanes from crude oil are broken down (cracked) into smaller, more useful molecules. The products are a mixture of:

• Smaller alkanes (used for fuels like petrol)

• Smaller alkenes (used to make plastics and other chemicals)

This is a more accurate description than just alkanes or alkenes alone.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 9:

The correct answer is A. High (650°C) — Alumina or silica.

Catalytic cracking of long-chain hydrocarbons from crude oil typically uses:

• High temperature (around 500–650°C, sometimes higher depending on the process)

• Catalyst such as alumina (Al₂O₃) or silica (SiO₂) (often zeolites, which are aluminosilicates)

• B — Iron is not typically used as a catalyst for cracking; iron catalysts are used in processes like the Haber process (ammonia synthesis).

• C & D — Low temperature (100°C) is far too low for cracking to occur efficiently.

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.

Question 10:

Let's check the carbon balance for each option:

Starting molecule: Decane → C₁₀H₂₂

• A. C₁₀H₂₂ → C₄H₁₀ + C₂H₄
  Left: 10 C, Right: 4 + 2 = 6 C → ❌ unbalanced.

• B. C₁₀H₂₂ → 2C₄H₁₀ + C₂H₄
  Left: 10 C, Right: 8 + 2 = 10 C ✅
  Left: 22 H, Right: (2×10) + 4 = 20 + 4 = 24 H → ❌ unbalanced.

• C. C₁₀H₂₂ → C₄H₁₀ + 2C₂H₄
  Left: 10 C, Right: 4 + 4 = 8 C → ❌ unbalanced.

• D. C₁₀H₂₂ → C₄H₁₀ + 3C₂H₄
  Left: 10 C, Right: 4 + 6 = 10 C ✅
  Left: 22 H, Right: 10 + (3×4) = 10 + 12 = 22 H ✅
  Balanced.

Correct answer: D. C₁₀H₂₂ → C₄H₁₀ + 3C₂H₄

*These A.I. responses have been individually checked to ensure they match the accepted answer, but explanations may still be incorrect. Responses may give guidance but the A.I. might not be able to answer the question! This is particularly the case for questions based on diagrams, which the A.I. typically cannot interpret.
Grade Gorilla uses Gemini, Deepseek and a range of other A.I. chatbots to generate the saved responses. Some answers have had human intervention for clarity or where the A.I. has not been able to answer the question.