Structure and uses of ethyl alcohol MCQs With Answer

Ethanol, commonly called ethyl alcohol, is a small polar molecule (C2H5OH) widely studied in pharmaceutical sciences for its structure, physical properties, reactions and practical uses. This concise guide focuses on the structure of ethanol, hydrogen bonding, acidity, methods of preparation (fermentation, ethylene hydration), major chemical reactions (oxidation, esterification, dehydration) and pharmaceutical applications such as solvent, preservative, disinfectant, excipient and tincture base. Designed for B.Pharm students, the content links molecular features to clinical and formulation roles, regulatory forms (absolute, denatured, USP) and safety/toxicology considerations. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the molecular formula of ethyl alcohol?

• C2H6O
• CH3OH
• C3H8O
• H2O

Correct Answer: C2H6O

Q2. What is the IUPAC name of ethyl alcohol?

• Methanol
• Ethanol
• Propanol
• Ethylene glycol

Correct Answer: Ethanol

Q3. Which functional group is present in ethyl alcohol?

• Aldehyde
• Ether
• Hydroxyl (alcohol)
• Carboxyl

Correct Answer: Hydroxyl (alcohol)

Q4. Which structural formula correctly represents ethanol?

• CH3–CH2–OH
• CH3–O–CH3
• CH3–CH=O
• CH3–CH2–NH2

Correct Answer: CH3–CH2–OH

Q5. Ethanol is classified as which type of alcohol?

• Primary alcohol
• Secondary alcohol
• Tertiary alcohol
• Aromatic alcohol

Correct Answer: Primary alcohol

Q6. Which intermolecular force is mainly responsible for ethanol’s relatively high boiling point?

• London dispersion forces only
• Hydrogen bonding
• Ion-dipole interactions
• Permanent dipole-dipole only

Correct Answer: Hydrogen bonding

Q7. Ethanol is miscible with water because of:

• Similar molecular weights
• Hydrogen bonding and polarity
• Nonpolar character
• Ionic dissociation

Correct Answer: Hydrogen bonding and polarity

Q8. The pKa of ethanol is approximately:

• –1
• 0.5
• 16
• 25

Correct Answer: 16

Q9. Which method is NOT commonly used for industrial production of ethanol?

• Fermentation of sugars
• Hydration of ethylene
• Direct oxidation of methane
• Biotechnological fermentation using yeast

Correct Answer: Direct oxidation of methane

Q10. What is “absolute alcohol”?

• 95% ethanol with water
• Anhydrous ethanol (nearly 100%)
• Denatured ethanol
• Ethanol mixed with methanol

Correct Answer: Anhydrous ethanol (nearly 100%)

Q11. The common azeotrope between ethanol and water boils at approximately:

• 78.4 °C
• 95.6 °C
• 78.1 °C
• 100 °C

Correct Answer: 78.1 °C

Q12. Denatured alcohol is primarily used in pharmaceuticals to:

• Improve taste for oral dosing
• Prevent consumption and avoid beverage taxes
• Increase viscosity
• Sterilize parenteral solutions

Correct Answer: Prevent consumption and avoid beverage taxes

Q13. Which enzyme catalyzes the primary metabolism of ethanol in the liver?

• Catalase
• Alcohol dehydrogenase (ADH)
• Aldehyde oxidase
• Acetyl-CoA synthetase

Correct Answer: Alcohol dehydrogenase (ADH)

Q14. The immediate product of ethanol oxidation by ADH is:

• Acetic acid
• Acetaldehyde
• Acetone
• Ethylene

Correct Answer: Acetaldehyde

Q15. Which reaction converts ethanol to ethene (ethylene)?

• Oxidation
• Dehydration
• Hydrogenation
• Saponification

Correct Answer: Dehydration

Q16. Ethanol reacts with carboxylic acids in presence of acid catalyst to form:

• Esters
• Amines
• Amides
• Peroxides

Correct Answer: Esters

Q17. Which of the following is a pharmaceutical use of ethanol?

• Antifungal tablet binder only
• Solvent, preservative, disinfectant and tincture base
• Only as an injectable anesthetic
• Only as an effervescent agent

Correct Answer: Solvent, preservative, disinfectant and tincture base

Q18. Ethanol acts as a cosolvent in formulations to:

• Decrease solubility of drugs
• Increase solubility of poorly water-soluble drugs
• Alter drug molecular weight
• Neutralize acidic drugs

Correct Answer: Increase solubility of poorly water-soluble drugs

Q19. In topical formulations ethanol primarily functions as a:

• Bulking agent
• Permeation enhancer and antiseptic
• Thickening agent
• Colorant

Correct Answer: Permeation enhancer and antiseptic

Q20. Which statement about ethanol’s vapor pressure vs water is correct at room temperature?

• Ethanol has lower vapor pressure than water
• Ethanol has higher vapor pressure than water
• Ethanol and water have identical vapor pressures
• Vapor pressure cannot be compared

Correct Answer: Ethanol has higher vapor pressure than water

Q21. The density of ethanol at 20 °C is approximately:

• 0.789 g/mL
• 1.00 g/mL
• 0.654 g/mL
• 1.25 g/mL

Correct Answer: 0.789 g/mL

Q22. Ethanol is used as a preservative in pharmaceutical tinctures because it:

• Promotes bacterial growth
• Denatures proteins and inhibits microbes
• Reduces shelf life
• Acts as a buffer

Correct Answer: Denatures proteins and inhibits microbes

Q23. Which physical property of ethanol most contributes to its use as a solvent for both polar and some nonpolar drugs?

• High viscosity
• Intermediate polarity and hydrogen-bonding ability
• Strong ionic character
• Very large molecular size

Correct Answer: Intermediate polarity and hydrogen-bonding ability

Q24. What is denatured alcohol?

• Ethanol purified to pharmaceutical grade
• Ethanol rendered unfit for drinking by additives
• Aqueous ethanol used in food products
• An ethanol–water azeotrope used in labs

Correct Answer: Ethanol rendered unfit for drinking by additives

Q25. Which reagent oxidizes ethanol to acetic acid under mild conditions?

• Sodium borohydride (NaBH4)
• PCC (pyridinium chlorochromate)
• Chromic acid (H2CrO4)
• Hydrogen gas with Pt

Correct Answer: Chromic acid (H2CrO4)

Q26. Ethanol forms hydrogen bonds with which part of a protein to exert antiseptic effects?

• Hydrophobic alkyl chains only
• Peptide backbone and side-chain polar groups
• Metal cofactors exclusively
• Disulfide bonds only

Correct Answer: Peptide backbone and side-chain polar groups

Q27. Which gas is commonly used to dehydrate ethanol to produce anhydrous ethanol industrially?

• Nitrogen
• Hydrogen
• Ethylene (as starting material for hydration), not a dehydrating gas
• Drying agents like molecular sieves (not a gas)

Correct Answer: Drying agents like molecular sieves (not a gas)

Q28. A major disadvantage of using ethanol as an excipient in oral medicines is:

• Complete lack of solubilizing ability
• Potential CNS effects and contraindications in some patients
• Inability to sterilize products
• It always precipitates active drugs

Correct Answer: Potential CNS effects and contraindications in some patients

Q29. Ethanol’s role in hand sanitizers is primarily due to:

• Enzymatic activity against bacteria
• Protein denaturation and membrane disruption
• Long-term residual activity on skin
• Emulsifying properties

Correct Answer: Protein denaturation and membrane disruption

Q30. Which is true about ethanol and cell membranes?

• Ethanol strengthens lipid bilayers
• Ethanol increases membrane fluidity and permeability
• Ethanol permanently crystallizes membranes
• Ethanol has no effect on membranes

Correct Answer: Ethanol increases membrane fluidity and permeability

Q31. Which form of ethanol is specified for pharmaceutical use in monographs like USP?

• Technical ethanol
• USP ethanol (pharmaceutical grade)
• Fuel ethanol
• Denatured industrial alcohol

Correct Answer: USP ethanol (pharmaceutical grade)

Q32. Ethanol acts as a cosolvent with water to enhance solubility of which drug type?

• Highly ionic salts only
• Hydrophobic (lipophilic) drugs with limited water solubility
• Gaseous drugs exclusively
• Proteins that denature in ethanol

Correct Answer: Hydrophobic (lipophilic) drugs with limited water solubility

Q33. Which test can distinguish ethanol from methanol in a formulation?

• Flame test only
• Gas chromatography analysis
• pH paper
• Density measurement only

Correct Answer: Gas chromatography analysis

Q34. Ethanol is often used in vaccine formulations as:

• Primary immunogen
• Preservative or solvent for stabilizers
• Adjuvant to enhance immune response
• Primary active antigen

Correct Answer: Preservative or solvent for stabilizers

Q35. Which byproduct is of toxicological concern when ethanol is metabolized?

• Ethylene oxide
• Acetaldehyde
• Formaldehyde
• Carbon monoxide

Correct Answer: Acetaldehyde

Q36. Ethanol can be used to precipitate which biological macromolecule from aqueous solution?

• Lipids only
• Proteins and nucleic acids (e.g., DNA precipitation)
• Inorganic salts only
• Simple sugars only

Correct Answer: Proteins and nucleic acids (e.g., DNA precipitation)

Q37. Standard proof system measures ethanol content; 100 proof corresponds to what % v/v ethanol?

• 100% v/v
• 50% v/v
• 40% v/v
• 75% v/v

Correct Answer: 50% v/v

Q38. Which is correct regarding ethanol’s flammability?

• Ethanol is non-flammable
• Ethanol is highly flammable; storage requires precautions
• Ethanol only ignites above 200 °C
• Ethanol will not burn in presence of oxygen

Correct Answer: Ethanol is highly flammable; storage requires precautions

Q39. In formulations, ethanol can interact with packaging materials; which is a common issue?

• It causes glass to melt
• It can extract plasticizers from polymer containers
• It polymerizes container surfaces
• It converts metals to salts

Correct Answer: It can extract plasticizers from polymer containers

Q40. Which analytical technique is commonly used to quantify ethanol concentration in biological samples?

• NMR only
• Gas chromatography with flame ionization detection (GC-FID)
• UV-Vis spectroscopy at 600 nm
• Titration with sodium hydroxide

Correct Answer: Gas chromatography with flame ionization detection (GC-FID)

Q41. Which statement about ethanol volatility in formulations is true?

• Ethanol is non-volatile and remains indefinitely
• Ethanol is volatile and may evaporate, affecting concentration
• Ethanol spontaneously polymerizes on exposure
• Ethanol becomes solid at room temperature

Correct Answer: Ethanol is volatile and may evaporate, affecting concentration

Q42. What is a common denaturant added to ethanol to make it unsuitable for drinking?

• Glycerin
• Denatonium benzoate or methanol (varies regionally)
• Pure water
• USP-grade saline

Correct Answer: Denatonium benzoate or methanol (varies regionally)

Q43. Which pathway becomes more significant for ethanol metabolism at high chronic intake?

• Glycolysis
• Microsomal ethanol-oxidizing system (MEOS; CYP2E1)
• Fatty acid beta-oxidation
• Urea cycle

Correct Answer: Microsomal ethanol-oxidizing system (MEOS; CYP2E1)

Q44. Ethanol’s boiling point (pure) is approximately:

• 100 °C
• 78 °C
• 50 °C
• 120 °C

Correct Answer: 78 °C

Q45. Which safety measure is important when handling concentrated ethanol in the lab?

• Ignition sources must be controlled due to flammability
• It is safe to use near open flames
• No ventilation is necessary
• Storage with oxidizers is recommended

Correct Answer: Ignition sources must be controlled due to flammability

Q46. Ethanol can denature proteins by:

• Enhancing ionic bonding only
• Disrupting hydrophobic interactions and hydrogen bonds
• Forming covalent crosslinks
• Increasing pH dramatically

Correct Answer: Disrupting hydrophobic interactions and hydrogen bonds

Q47. Which pharmaceutical formulation commonly contains ethanol as solvent?

• Intravenous saline only
• Tinctures, elixirs and some topical solutions
• All solid tablets exclusively
• Gasoline-based inhalers

Correct Answer: Tinctures, elixirs and some topical solutions

Q48. Which property of ethanol explains its ability to dissolve both polar and some nonpolar compounds?

• Completely nonpolar nature
• Amphipathic character with both polar hydroxyl and nonpolar ethyl group
• Highly ionic structure
• Large aromatic ring

Correct Answer: Amphipathic character with both polar hydroxyl and nonpolar ethyl group

Q49. Which reaction yields ethyl chloride from ethanol?

• Oxidation with PCC
• Treatment with thionyl chloride (SOCl2) or HCl/ZnCl2 (Lucas-type)
• Dehydration to ethene only
• Hydrogenation with H2/Pd

Correct Answer: Treatment with thionyl chloride (SOCl2) or HCl/ZnCl2 (Lucas-type)

Q50. In formulation labeling, ethanol concentration is often expressed as:

• ppm only
• % v/v or % w/w depending on context
• Molarity only
• Proof only (no percent)

Correct Answer: % v/v or % w/w depending on context

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