Alcohols Haloalkanes and Analysis Practice Quiz (22 questions)

1. Which structural feature defines an alcohol in organic chemistry?

A. A carbon chain containing a carbonyl group

B. A carbon chain bonded to an –OH group

C. A carbon chain joined to an amino group

D. A carbon chain bonded to a halogen atom

Answer: (B)

Explanation

Alcohols are defined by the presence of a hydroxyl group, written as –OH, and commonly have the formula $\mathrm{C_nH_{2n+1}OH}$. A haloalkane instead contains a carbon–halogen bond, while carbonyl and amino groups define different functional classes.

2. How is an alcohol classified as primary, secondary, or tertiary?

A. By the number of oxygen atoms present in the molecule

B. By the number of hydrogen atoms bonded to oxygen

C. By the number of carbon atoms bonded to the carbon carrying –OH

D. By the position of the longest carbon chain

Answer: (C)

Explanation

Alcohol classification depends on how many carbon atoms are attached to the carbon bearing the hydroxyl group. The total oxygen content, chain length, and hydrogen count do not determine whether an alcohol is primary, secondary, or tertiary.

3. Why can many alcohols dissolve in water?

A. Their carbon chains form ionic bonds with water

B. Their oxygen atom can form hydrogen bonds with water

C. Their hydrogen atoms attract water through metallic bonding

D. Their molecules contain no nonpolar regions

Answer: (B)

Explanation

Alcohols are polar because oxygen is electronegative, allowing their hydroxyl groups to hydrogen-bond with water molecules. Alkanes lack this hydrogen-bonding interaction, so their water solubility is much lower.

4. What are the main products when an alcohol undergoes complete combustion in air?

A. Carbon dioxide and water, with substantial energy released

B. A haloalkane and hydrogen, with substantial energy absorbed

C. An alkene and water, with substantial energy released

D. An aldehyde and oxygen, with substantial energy absorbed

Answer: (A)

Explanation

Complete alcohol combustion produces carbon dioxide and water while releasing substantial energy. Formation of an alkene and water is associated with dehydration rather than combustion.

5. What happens during nucleophilic substitution of an alcohol with a halogenating agent?

A. The hydroxyl group is oxidised to form a carboxylic acid

B. A hydrogen atom is replaced by oxygen to form an aldehyde

C. The hydroxyl group is replaced by a halogen to form a haloalkane

D. Water is removed from the alcohol to form an alkene

Answer: (C)

Explanation

In this substitution reaction, the alcohol’s –OH group is replaced by a halogen, producing a haloalkane. Removing water to produce an alkene is an elimination or dehydration process, not nucleophilic substitution.

6. Which oxidation sequence correctly describes primary, secondary, and tertiary alcohols?

A. Primary alcohols form ketones then acids; secondary alcohols form aldehydes; tertiary alcohols oxidise readily

B. Primary alcohols form aldehydes then acids; secondary alcohols form ketones; tertiary alcohols oxidise with difficulty

C. Primary alcohols form alkenes; secondary alcohols form acids; tertiary alcohols form aldehydes

D. Primary alcohols form acids directly; secondary alcohols form alkenes; tertiary alcohols form ketones

Answer: (B)

Explanation

Primary alcohols oxidise first to aldehydes and then to carboxylic acids, whereas secondary alcohols form ketones. Tertiary alcohols are not easily oxidised under typical conditions, so the other sequences misassign the oxidation products.

7. What structural feature characterises a haloalkane?

A. A hydrogen-bonded carbon–oxygen group

B. A carbon–carbon double bond

C. A polar carbon–halogen bond

D. A carbon–nitrogen triple bond

Answer: (C)

Explanation

Haloalkanes contain polar carbon–halogen bonds because halogens are more electronegative than carbon. An alcohol contains a carbon–oxygen hydroxyl group, while the other choices describe different structural features.

8. Why does haloalkane reactivity generally increase down the halogen group?

A. The carbon–halogen bond becomes stronger as halogen relative molecular mass increases

B. The carbon atom becomes more electronegative than the halogen

C. The carbon–halogen bond becomes weaker as halogen relative molecular mass increases

D. The haloalkane becomes less polar as its carbon chain shortens

Answer: (C)

Explanation

Reactivity increases down the group because increasing halogen size and relative molecular mass are associated with lower carbon–halogen bond enthalpy. The weaker bond is therefore easier to break during reaction.

9. What products are formed when a haloalkane reacts with aqueous hydroxide compared with ethanolic potassium hydroxide?

A. Aqueous hydroxide forms an alkene, whereas ethanolic potassium hydroxide forms an alcohol

B. Both conditions form an alcohol through identical substitution pathways

C. Aqueous hydroxide forms an alcohol, whereas ethanolic potassium hydroxide forms an alkene

D. Both conditions form an alkene through identical elimination pathways

Answer: (C)

Explanation

Aqueous sodium or potassium hydroxide promotes nucleophilic substitution, replacing the halogen with hydroxyl to form an alcohol. Ethanolic potassium hydroxide promotes elimination, removing elements of water and producing an alkene.

10. During a nucleophilic substitution, what happens at the carbon attached to the halogen?

A. A nucleophile accepts an electron pair while the carbon–halogen bond forms

B. A base removes a proton while a carbon–hydrogen bond breaks

C. A halogen donates an electron pair while the carbon–oxygen bond breaks

D. A nucleophile donates an electron pair while the carbon–halogen bond breaks

Answer: (D)

Explanation

The nucleophile attacks the electron-deficient carbon by donating an electron pair, and the carbon–halogen bond breaks. A base removing a proton describes the contrasting role of a base in elimination rather than the nucleophilic substitution step.

11. What precipitate is expected when iodide ions are tested with silver nitrate?

A. A white precipitate of silver chloride

B. A pale blue precipitate of silver iodide

C. A cream precipitate of silver bromide

D. A yellow precipitate of silver iodide

Answer: (D)

Explanation

Iodide produces yellow silver iodide in the silver nitrate hydrolysis test. Chloride instead forms a white precipitate, while bromide forms a cream precipitate.

12. How do CFCs catalyse the breakdown of ozone in the atmosphere?

A. Visible light releases oxygen radicals that permanently consume chlorine compounds

B. Water vapour releases bromine ions that convert ozone directly into hydrogen peroxide

C. UV radiation releases chlorine radicals that repeatedly promote ozone decomposition

D. Heat releases carbon radicals that prevent oxygen molecules from recombining

Answer: (C)

Explanation

UV photolysis of CFCs forms chlorine radicals, which catalyse ozone breakdown and are regenerated during the process. The chlorine radical therefore acts catalytically rather than being permanently consumed in one reaction.

13. Why is reflux used when an organic reaction must be heated for an extended period?

A. The condenser removes the lowest-boiling product so that it can be collected separately

B. The condenser returns vapours to the flask, preventing product loss during continued heating

C. The apparatus separates immiscible liquids by allowing their layers to settle

D. The apparatus cools the reaction mixture so that oxidation stops before completion

Answer: (B)

Explanation

Reflux continuously heats the mixture while condensing vapours back into the flask, allowing prolonged reaction without losing volatile material. Removing and collecting a volatile product is the purpose of distillation, not reflux.

14. A mixture contains two liquids with different boiling points. Which principle allows distillation to separate them?

A. The more soluble liquid dissolves in the condenser, then crystallises during cooling

B. The liquid with the higher boiling point evaporates first, then remains in the flask

C. The denser liquid settles first, then is drained through a separating funnel

D. The liquid with the lower boiling point evaporates first, then condenses for collection

Answer: (D)

Explanation

Distillation separates liquids according to boiling point: the lower-boiling liquid vaporises first, condenses, and is collected. Separation based on density and immiscible layers belongs to separating-funnel techniques.

15. What best describes the sequence in a multi-stage organic synthesis?

A. A solvent is converted through purification stages into the desired reactant

B. Several products are mixed directly until one intermediate becomes the starting reactant

C. A starting reactant is converted through intermediates into the desired product

D. A desired product is decomposed through intermediates into the starting reactant

Answer: (C)

Explanation

A multi-stage synthesis proceeds from a starting reactant through one or more intermediates to the desired product. An intermediate is formed during the route, whereas the starting reactant initiates it.

16. Which pairing correctly matches an identification test with the substance it detects?

A. Bromine water tests for primary alcohols

B. Aqueous silver nitrate in ethanol tests for unsaturation

C. Tollens’ reagent tests for aldehydes

D. Acidified potassium dichromate(VI) tests for haloalkanes

Answer: (C)

Explanation

Tollens’ reagent is used to test for aldehydes. Bromine water tests for unsaturation, acidified potassium dichromate(VI) tests for primary and secondary alcohols, and aqueous silver nitrate in ethanol tests for haloalkanes.

17. What does infrared spectroscopy measure to identify functional groups?

A. Changes in boiling point caused by intermolecular forces

B. Absorption caused by vibrating covalent bonds

C. Ion mass-to-charge ratios after molecular fragmentation

D. Emission produced when electrons return to lower orbitals

Answer: (B)

Explanation

Infrared spectroscopy identifies functional groups through the absorption of infrared radiation by vibrating covalent bonds. Measuring ion mass-to-charge ratios is the principle of mass spectrometry, not infrared spectroscopy.

18. Which infrared absorption best indicates an alcohol O–H bond?

A. A sharp peak at 1680–1750 cm⁻¹

B. A broad peak at 3230–3550 cm⁻¹

C. A broad peak at 2500–3300 cm⁻¹ overlapping C–H absorption

D. A sharp peak at 1620–1680 cm⁻¹

Answer: (B)

Explanation

An alcohol O–H bond produces a broad absorption at 3230–3550 cm⁻¹. The 2500–3300 cm⁻¹ broad region that overlaps the C–H region is characteristic of a carboxylic-acid O–H bond.

19. An infrared spectrum shows a sharp absorption at 1700 cm⁻¹; which bond is most consistent with this signal?

A. A carbonyl C=O bond

B. A carboxylic-acid O–H bond

C. An alcohol O–H bond

D. An alkene C=C bond

Answer: (A)

Explanation

A sharp absorption at 1700 cm⁻¹ falls within the C=O range of 1680–1750 cm⁻¹. A C=C bond absorbs sharply at the lower range of 1620–1680 cm⁻¹, while O–H absorptions are broad.

20. What quantity does mass spectrometry measure to identify molecules and determine relative molecular mass?

A. The wavelengths absorbed by functional groups

B. The mass-to-charge ratios of ions

C. The frequencies of vibrating covalent bonds

D. The boiling points of separated molecular components

Answer: (B)

Explanation

Mass spectrometry measures ions according to their mass-to-charge ratios, allowing molecules to be identified and relative molecular masses to be determined. Vibrating-bond absorption is measured by infrared spectroscopy.

21. Which sequence correctly describes the main stages of time-of-flight mass spectrometry?

A. Acceleration, fragmentation, absorption, detection, and weighing

B. Ionisation, absorption, separation, combustion, and analysis

C. Detection, ionisation, drift, acceleration, and analysis

D. Ionisation, acceleration, drift, detection, and analysis

Answer: (D)

Explanation

Time-of-flight mass spectrometry proceeds through ionisation, acceleration, ion drift, detection, and analysis of flight times and currents. Absorption of infrared radiation is associated with infrared spectroscopy rather than this mass-spectrometric sequence.

22. How can the molecular ion peak be recognized and used in a mass spectrum?

A. It is the peak furthest right, and its m/z value gives the relative molecular mass

B. It is the peak furthest left, and its m/z value identifies the smallest fragment

C. It is the tallest peak, and its intensity gives the relative molecular mass

D. It is the first fragment peak, and its intensity gives the isotope abundance

Answer: (A)

Explanation

The molecular ion peak is furthest to the right, and its m/z value can be used to calculate the relative molecular mass. The tallest peak is not necessarily the molecular ion because fragment ions can have greater intensity.