Physical and Chemical Properties of Alcohols - UNSOLVED PRACTICE SET
Chapter: Alcohols Phenols and Ethers | Topic: Physical and Chemical Properties of Alcohols
PHYSICAL AND CHEMICAL PROPERTIES OF ALCOHOLS - UNSOLVED PRACTICE SET
Topic: Physical and Chemical Properties of Alcohols
Multiple Choice Questions
Q1. The boiling point of alcohols is higher than corresponding alkanes because of:
- Higher molecular mass
- Hydrogen bonding
- Dipole-dipole interactions
- All of the above
Q2. The solubility of alcohols in water decreases as the alkyl chain length increases because:
- The -OH group becomes less polar
- The hydrophobic alkyl group dominates
- Hydrogen bonding decreases
- The molecular mass decreases
Q3. Alcohols react with sodium to give:
- Sodium alkoxide and hydrogen
- Sodium alkoxide and water
- Alkene and hydrogen
- No reaction
Q4. The acidic strength of alcohols compared to water is:
- Greater than water
- Less than water
- Equal to water
- Variable
Q5. Which of the following is the strongest acid?
- CH₃OH
- C₂H₅OH
- (CH₃)₃COH
- C₆H₅OH
Q6. The reaction of alcohol with carboxylic acid in presence of H₂SO₄ is called:
- Dehydration
- Esterification
- Oxidation
- Reduction
Short Answer Questions
Q7. Explain why ethanol is soluble in water in all proportions while butanol is only partially soluble.
Q8. Why do alcohols have higher boiling points than ethers of comparable molecular mass?
Q9. Write the reaction of ethanol with sodium metal. Why is this reaction slower than the reaction of sodium with water?
Q10. Arrange the following in order of increasing acidic strength: methanol, ethanol, tert-butanol, phenol. Give reason.
Q11. What is the Lucas test? How does it distinguish between primary, secondary, and tertiary alcohols?
Q12. Your mother uses ethanol-based hand sanitizer. Why is ethanol effective in killing germs? What property of alcohols is utilized here?
Long Answer Questions
Q13. (a) Discuss the physical properties of alcohols with respect to:
(i) Boiling points
(ii) Solubility in water
(iii) Viscosity
Explain each property in terms of intermolecular forces.
Q14. (a) Discuss the chemical properties of alcohols with respect to:
(i) Reaction with metals (Na, K, Al)
(ii) Reaction with hydrogen halides
(iii) Reaction with PCl₅, PCl₃, SOCl₂
(iv) Dehydration
(v) Oxidation
Write one reaction for each.
Q15. (a) Explain why alcohols are weaker acids than water but stronger acids than alkanes.
(b) Arrange the following in order of increasing acidic strength and explain:
H₂O, CH₃OH, C₂H₅OH, (CH₃)₃COH, C₆H₅OH
(c) How does the acidic strength of alcohols change with:
(i) Increase in alkyl group size?
(ii) Presence of electron-withdrawing groups?
Numerical / Application-Based Problems
Q16. The following table gives boiling point data for some compounds:
| Compound | Molecular Mass (g/mol) | Boiling Point (°C) |
|---|---|---|
| CH₃OH | 32 | 65 |
| CH₃CH₃ | 30 | -89 |
| CH₃F | 34 | -78 |
| CH₃NH₂ | 31 | -6 |
| C₂H₅OH | 46 | 78 |
| C₂H₅CH₃ | 44 | -42 |
| CH₃OCH₃ | 46 | -24 |
(a) Compare the boiling points of CH₃OH and CH₃CH₃ despite similar molecular masses. Explain the difference.
(b) Compare the boiling points of C₂H₅OH and CH₃OCH₃ despite having the same molecular mass. Explain.
(c) Plot a graph of boiling point vs. molecular mass for CH₃OH, C₂H₅OH, and predict the boiling point of C₃H₇OH.
(d) Calculate the difference in boiling points between each alcohol and its corresponding alkane. What trend do you observe?
(e) A student claims that hydrogen bonding is the only factor determining boiling points. Use the data to evaluate this claim.
Q17. The following data relates to the solubility of alcohols in water:
| Alcohol | Solubility (g/100 mL water at 20°C) |
|---|---|
| Methanol | Miscible |
| Ethanol | Miscible |
| Propan-1-ol | Miscible |
| Butan-1-ol | 7.9 |
| Pentan-1-ol | 2.7 |
| Hexan-1-ol | 0.6 |
| Heptan-1-ol | 0.2 |
(a) Explain why solubility decreases as the carbon chain length increases.
(b) Calculate the number of carbon atoms at which the alcohol becomes practically insoluble in water.
(c) Octan-1-ol has a solubility of 0.05 g/100 mL. Predict the solubility of decan-1-ol.
(d) Branched alcohols are more soluble than straight-chain alcohols with the same number of carbons. Explain why.
(e) A perfume manufacturer wants to use an alcohol as a solvent that is partially soluble in water but soluble in oils. Which alcohol from the table would be most suitable? Why?
Q18. In a school science project, students investigate the properties of alcohols in everyday life.
(a) A student finds that her father's aftershave contains ethanol. Why is ethanol used in aftershave? (Consider volatility, cooling effect, and antiseptic properties.)
(b) Another student learns that glycerol (propane-1,2,3-triol) is used in moisturizers. Why is glycerol effective as a moisturizer? (Consider hydrogen bonding with water.)
(c) A third student discovers that methanol is added to ethanol to make it unfit for drinking (denatured alcohol). Why is methanol dangerous if consumed? (Consider metabolic products.)
(d) The students test the viscosity of different alcohols: methanol, ethanol, propan-1-ol, and glycerol. Arrange them in order of increasing viscosity and explain.
(e) The teacher asks: "If you were designing a hand sanitizer, what concentration of ethanol would you choose and why? What other ingredients would you add?" Give your answer with reasoning.