Question 1:

The correct answer is A. CₙH₂ₙ₊₂.

Alkanes are saturated hydrocarbons with single bonds only.

• A. CₙH₂ₙ₊₂ — Correct, e.g., methane CH₄ (n=1), ethane C₂H₆ (n=2).

• B. CₙH₂ₙ — Alkenes (or cycloalkanes).

• C. CₙH₂ₙ₊₁ — Alkyl group (not a complete hydrocarbon series).

• D. CₙH₂ₙ₋₂ — Alkynes or other unsaturated hydrocarbons.

*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. a compound containing only carbon and hydrogen.

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

• A — Incorrect, as crude oil contains many other compounds, not just hydrocarbons.

• B — Incorrect, as hydrocarbons include alkynes, cycloalkanes, arenes, etc., not just alkanes or alkenes.

• C — Incorrect (incomplete and misleading), as it says "a compound containing carbon and hydrogen" but does not specify only — that would allow other elements to be present.

• D — Correct, precise definition.

*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 C. butane, propane, ethane, methane.

The question asks for the names in order of decreasing number of carbon atoms (from highest to lowest carbon count):

• Butane — 4 carbon atoms

• Propane — 3 carbon atoms

• Ethane — 2 carbon atoms

• Methane — 1 carbon atom

So the correct order is butane → propane → ethane → methane.

*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:

The correct answer is D. all of the above.

Members of a homologous series:

• A. have the same functional group — This gives them similar chemical reactions.

• B. have the same general formula — For example, alkanes: CₙH₂ₙ₊₂.

• C. have physical properties which show a gradual change — For example, boiling point increases as molecular size increases.

Therefore, all of the above are correct characteristics of a homologous series.

*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:

The correct answer is D.

For the alkene homologous series:

• General formula = CₙH₂ₙ

• Functional group = C=C (carbon-carbon double bond)

Checking the options:

• A & B have CₙH₂ₙ₊₂ (alkane formula) → incorrect.

• C has CₙH₂ₙ (correct formula) but C–H bond as functional group (incorrect; C–H is not the characteristic functional group of alkenes).

• D has CₙH₂ₙ and C=C → correct.

*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:

The correct answer is A.

• Alkanes are saturated hydrocarbons (only single C–C bonds, maximum number of hydrogen atoms).

• Alkenes are unsaturated hydrocarbons (contain at least one C=C double bond, so fewer hydrogen atoms than the corresponding alkane).

*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:

Analysis of Molecules

Based on the structures provided:

• W (Propane): An alkane (saturated hydrocarbon).
• X (Ethanol): An alcohol (saturated).
• Y (Propene): An alkene (unsaturated hydrocarbon) containing a carbon-carbon double bond.
• Z (Ethane): An alkane (saturated hydrocarbon).

Correct Answer for Q7: B. Y only

Bromine water is a test for unsaturation. The orange-brown bromine adds across the C=C double bond in an addition reaction, causing the solution to turn colourless. Only molecule Y has a double bond.

*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:

Analysis of Molecules

Based on the structures provided:

• W (Propane): An alkane (saturated hydrocarbon).
• X (Ethanol): An alcohol (saturated).
• Y (Propene): An alkene (unsaturated hydrocarbon) containing a carbon-carbon double bond.
• Z (Ethane): An alkane (saturated hydrocarbon).

8. Correct Answer for Q8: B. Y only

In organic chemistry, "unsaturated" refers to molecules containing at least one carbon-carbon double or triple bond. Molecule Y (propene) is the only structure shown with a double bond. Molecules W, X, and Z contain only single bonds.

*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 D. carbon dioxide and water.

Complete combustion of any substance containing carbon, hydrogen, and oxygen (e.g., alcohols, carbohydrates, hydrocarbons) — when burned in excess oxygen — produces only carbon dioxide (CO₂) and water (H₂O).

Any oxygen present in the original molecule simply means less oxygen is required from the air, but the products remain the same: CO₂ and H₂O.

*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:

The correct answer is D. C₂H₄ + Br₂ → C₂H₄Br₂.

This is an addition reaction of bromine to ethene (an alkene).
The double bond in ethene breaks, and each carbon atom bonds with a bromine atom, producing 1,2-dibromoethane (C₂H₄Br₂).

Checking the options:

• A — Uses ethane (C₂H₆, an alkane), which reacts with bromine by substitution (not addition), giving C₂H₅Br + HBr — incorrect for this question.

• B — Incorrect products; would require removal of hydrogen atoms, not typical here.

• C — Formula C₂H₄Br is impossible (unbalanced/unstable); also suggests substitution-like product.

• D — Correct addition product, balanced.

*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.