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Question (21)

QN0035992

A carbon compound contains an –OH functional group. Which class does it belong to?

(A) Alcohol
(B) Ketone
(C) Aldehyde
(D) Alkene

Correct Answer: A

Explanation:

The –OH group is the functional group characteristic of alcohols.

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Question (22)

QN0035993

Four compounds have the same functional group but contain 1, 2, 3 and 4 carbon atoms respectively. Their chemical properties are expected to be:

(A) Completely unrelated
(B) Similar, while physical properties show gradual changes
(C) Identical in every property
(D) Dependent only on molecular mass

Correct Answer: B

Explanation:

Members of a homologous series have similar chemical properties because of the same functional group, while physical properties such as melting and boiling points show gradual changes.

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Question (23)

QN0035994

If the molecular mass of successive members of a homologous series increases by 14 u, which group accounts for this regular increase?

(A) CH
(B) CH₂
(C) CH₃
(D) C₂H₂

Correct Answer: B

Explanation:

Successive homologues differ by CH₂. Its mass is 12 + 2 = 14 u.

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Question (24)

QN0035995

A fuel burns with a yellow flame and produces black soot. Which condition is most likely responsible?

(A) Complete combustion with excess oxygen
(B) Incomplete combustion
(C) Absence of carbon
(D) Formation of an ionic compound

Correct Answer: B

Explanation:

Limited oxygen can cause incomplete combustion and formation of soot. Unsaturated compounds also generally produce yellow, smoky flames.

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Question (25)

QN0035996

A cooking vessel becomes blackened underneath while a gas stove is being used. What is the most reasonable inference?

(A) Fuel is burning completely.
(B) Air holes may be blocked, causing incomplete combustion.
(C) The vessel is producing carbon.
(D) The fuel contains no carbon.

Correct Answer: B

Explanation:

The chapter states that blackening indicates incomplete combustion, often because the air holes are blocked.

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Question (26)

QN0035997

Complete combustion of methane produces which combination of products?

(A) CO and H₂
(B) C and H₂O
(C) CO₂ and H₂O
(D) CH₃OH and O₂

Correct Answer: C

Explanation:

Methane burns in oxygen to produce carbon dioxide, water, heat and light.

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Question (27)

QN0035998

How many oxygen atoms are present in the products when two molecules of methane undergo complete combustion?

(A) 2
(B) 4
(C) 6
(D) 8

Correct Answer: D

Explanation:

2CH₄ + 4O₂ → 2CO₂ + 4H₂O. Products contain 4 oxygen atoms in CO₂ and 4 in H₂O, making 8 oxygen atoms.

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Question (28)

QN0035999

A student compares a saturated hydrocarbon with an unsaturated hydrocarbon under similar burning conditions. Which observation is generally expected for the unsaturated compound?

(A) Cleaner flame only
(B) Yellow flame with more black smoke
(C) No combustion
(D) Formation of an ionic solid

Correct Answer: B

Explanation:

Unsaturated carbon compounds generally burn with a yellow flame and produce black smoke/soot.

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Question (29)

QN0036000

Ethanol is oxidised to ethanoic acid using an oxidising agent. Which change best represents oxidation in this case?

(A) Removal of carbon
(B) Addition of oxygen
(C) Addition of hydrogen only
(D) Formation of a hydrocarbon

Correct Answer: B

Explanation:

Oxidising agents such as alkaline potassium permanganate and acidified potassium dichromate add oxygen during conversion of alcohols to acids.

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Question (30)

QN0036001

A reaction converts an unsaturated hydrocarbon into a saturated hydrocarbon by adding hydrogen in the presence of nickel. What type of reaction is this?

(A) Substitution
(B) Addition
(C) Neutralisation
(D) Esterification

Correct Answer: B

Explanation:

Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as nickel or palladium to form saturated hydrocarbons.

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Question (21)

A carbon compound contains an –OH functional group. Which class does it belong to?

Explanation:

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Question (22)

Four compounds have the same functional group but contain 1, 2, 3 and 4 carbon atoms respectively. Their chemical properties are expected to be:

Explanation:

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Question (23)

If the molecular mass of successive members of a homologous series increases by 14 u, which group accounts for this regular increase?

Explanation:

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Question (24)

A fuel burns with a yellow flame and produces black soot. Which condition is most likely responsible?

Explanation:

Link:

Question (25)

A cooking vessel becomes blackened underneath while a gas stove is being used. What is the most reasonable inference?

Explanation:

Link:

Question (26)

Complete combustion of methane produces which combination of products?

Explanation:

Link:

Question (27)

How many oxygen atoms are present in the products when two molecules of methane undergo complete combustion?

Explanation:

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Question (28)

A student compares a saturated hydrocarbon with an unsaturated hydrocarbon under similar burning conditions. Which observation is generally expected for the unsaturated compound?

Explanation:

Link:

Question (29)

Ethanol is oxidised to ethanoic acid using an oxidising agent. Which change best represents oxidation in this case?

Explanation:

Link:

Question (30)

A reaction converts an unsaturated hydrocarbon into a saturated hydrocarbon by adding hydrogen in the presence of nickel. What type of reaction is this?

Explanation:

Link:

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