Alcohol Chemistry Questions

In organic chemistry, an alcohol is an organic molecule with at least one hydroxyl group attached to a carbon atom that is saturated. It is frequently abbreviated as ROH. Alcohols are considered organic derivatives of water molecules in which an alkyl group has replaced one of the hydrogen atoms.

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Alcohol Chemistry Questions with Solutions

Q1. Lucas reagent is the solution of

1. Anhydrous zinc chloride and concentrated hydrochloric acid
2. Anhydrous copper chloride and concentrated hydrochloric acid
3. Anhydrous zinc chloride and dilute hydrochloric acid
4. Anhydrous copper chloride and dilute hydrochloric acid

Answer: (a), Lucas reagent is the solution of anhydrous zinc chloride and concentrated hydrochloric acid. It is used to differentiate primary, secondary and tertiary alcohols.

Q2. Converting sugar into alcohol is known as

1. Homogenisation
2. Fermentation
3. Pasteurisation
4. None of the above

Answer: (b), The process of converting sugar into alcohol is known as fermentation.

Q3. Dehydration of alcohol is an example of

1. Substitution Reaction
2. Addition Reaction
3. Elimination Reaction
4. Redox Reaction

Answer: ( c ) , Dehydration of alcohol is an example of an elimination reaction. Elimination is an organic reaction in which several atoms are removed from a molecule.

Q4. Which of the following alcohol will not give a Lucas reagent test?

1. N-butanol
2. Isobutyl alcohol
3. Tert-butyl alcohol
4. sec-butyl alcohol

Answer: (a), Isobutyl alcohol does not give a Lucas reagent test. Lucas reagent is a solution of anhydrous zinc chloride and concentrated hydrochloric acid solution. It is used to differentiate primary, secondary and tertiary alcohols.

Q5. Which of the following is formed when glycerol is heated with oxalic acid at 503K?

1. Allyl alcohol
2. Benzyl alcohol
3. Phenol
4. None of the above

Answer: (a), Allyl alcohol is formed when glycerol is heated with oxalic acid at 503K.

Q6. Draw the structure of glycerol and write its IUPAC name?

Answer: Structure of glycerol:

The IUPAC name of glycerol is trihydric alcohol.

Q7. Name a reagent that can be used to convert ethanol to ethanoic acid.

Answer: Strong reagents like acidified KMnO₄ and K₂Cr₂O₇ can be used to convert ethanol to ethanoic acid.

Q8. Why do alcohol and ether of relative molecular mass have different boiling points?

Answer: The difference in the boiling point of alcohol and ether of relative molecular mass is because ether is less polar and does not have intermolecular hydrogen bonding.

Q9. Why is 2-chloro ethanol more acidic than ethanol?

Answer: Because chlorine is an electron-withdrawing group, 2-chloro ethanol is more acidic than ethanol. It reduces the electron density above O-H. Consequently destabilizing it. Ethanol, on the other hand, contains an alkyl group that donates electrons; this decreases the electron density over the O-H, so stabilizing it. Therefore, 2-chloro ethanol has a higher acidity than ethanol.

Q10. Name a reagent that can be used to convert ethanol to ethanal.

Answer: Pyridinium chlorochromate (PCC) can be used to convert ethanol to ethanal.

Q11. Draw the structures of the isomers of alcohols with the molecular formula C₄H₁₀O. Which of these will exhibit optical activity?

Answer: There are four isomers of alcohols with the molecular formula C₄H₁₀O.

• Butanol
• 2- Methyl propanol
• 2-methyl propan-2-ol
• Butan-2-ol

Out of the four isomers mentioned above, Butan-2-ol will show optical activity and exist in two optically active forms.

Q12. Alcohols are more soluble in water than the hydrocarbons of relative molecular masses. Explain Why?

Answer: Alcohols are more soluble in water than hydrocarbons with equal molecular weights because alcohols create hydrogen bonds with water molecules and disrupt the existing hydrogen bonds between water molecules. Thus, they are water-soluble. Hydrocarbon, on the other hand, cannot establish hydrogen bonds with water molecules. Therefore, they are water-insoluble.

Q13. Give a chemical test used in distinguishing 2-propanol and 2-methyl-2-propanol.

Answer: Using the iodoform test, we can identify between 2-propanol and 2-methyl-2-propanol. 2-Propanol is an alcohol of secondary structure. It interacts with iodine and sodium hydroxide to produce a yellow iodoform precipitate. 2-methyl-2 propanol, in contrast, does not respond to this test. Using the iodoform test, we can distinguish between 2-propanol and 2-methyl-2-propanol rapidly.

Q14. What is Luca’s reagent?

Answer: Luca’s reagent is the solution of anhydrous zinc chloride and concentrated hydrochloric acid. It is used to differentiate primary, secondary and tertiary alcohols.

Q15. Differentiate between alcohol and phenol.

Answer:

S. No.	Alcohol	Phenol
1.	It has at least one OH group attached to a carbon atom.	It has at least one OH group linked to aromatic hydrocarbons.
2.	They are less acidic than phenol.	They are more acidic than alcohol.
3.	They are predominantly colourless liquids.	They are primarily colourless solids that exist as a crystal at STP.
4.	They don’t turn blue litmus paper red.	They turn blue litmus paper red.
5.	They are primarily used in the ink and pharmaceutical industries.	They are mainly used in medicinal products as antiseptic agents.