Solved Exercise, Chem-12, Ch-11

ALCOHOLS, PHENOLS & ETHERS

FILL IN THE BLANKS

Q.01: Fill in the blanks:

(i) Primary, secondary and tertiary alcohols can be identified by _______ test. (Lucas)

(ii) Oxidation of ________ alcohols give ketones. (secondary)

(iii) Alcohols on heating with ________ give alkenes at high temperature. (H₂SO₄)

(iv) Alcohols have ________ boiling points than ethers due to stronger hydrogen bonding. (high)

(v) Williamsons synthesis is used to prepare _______. (ether)

(vi) ________is also called wood spirit. (methanol)

(vii) Carbolic acid is the other name of ________. (phenol)

(viii) Primary, secondary and tertiary alcohols can be prepared by reacting Grignard reagent with ________, ________ and ________. (formaldehyde, acetaldehyde & acetone)

(ix) Alcohols and ________ react to produce esters. (carboxylic acids)

(x) ________ is used as anti-freezing agent in automobile radiator. (glycol)

(xi) The process of conversion of starch into alcohol with the help of microorganisms is called _______. (fermentation)

(xii) Ketones on reduction give ________ alcohols. (secondary)

TRUE/FALSE

Q.02: Indicate True or False:

(i) Methylated spirit contains 95% methyl alcohol and 5% ethyl alcohol. (FALSE)

CORRECT: Methylated spirit contains 10% methyl alcohol and 90% ethyl alcohol.

(ii) Ethyl alcohol is a very good anti-freezing agent. (FALSE)

CORRECT: Methyl alcohol is a very good anti-freezing agent.

(iii) Methanol is also called wood spirit. (TRUE)

(iv) Only 14% ethyl alcohol can be prepared by fermentation. (TRUE)

(v) Ethers do not show hydrogen bonding. (TRUE)

(vi) Alcohols are more acidic than phenols. (FALSE)

CORRECT: Alcohols are less acidic than phenols.

(vii) Phenol is more soluble in water than lower alcohols. (FALSE)

CORRECT: Phenol is less soluble in water than lower alcohols.

(viii) Alcohols are more basic than ethers. (FALSE)

CORRECT: Alcohols are less basic than ethers.

(ix) Ethers have higher boiling points than alcohols and phenols. (FALSE)

CORRECT: Ethers have lower boiling points than alcohols and phenols.

(x) Methanol and ethanol can be distinguished by iodoform test. (TRUE)

MCQs

Q.03: Multiple choice questions.

(i) Which compound shows hydrogen bonding?                

(a) C₂H₆                                          

(b) C₂H₅Cl

(c) CH₃-O-CH₃                                

(d) C₂H₅OH

ANSWER: (d) C₂H₅OH

EXPLANATION: Ethanol has highly partial positive H-atom attached with strongly partial negative O-atom, having two lone pair of electrons. That’s why it has hydrogen bonding among its molecules.

(ii) Which compound shows maximum hydrogen bonding with water?                   

(a) CH₃OH                                      

(b) C₂H₅OH

(c) CH₃-O-CH₃                                

(d) C₆H₅OH

ANSWER: (a) CH₃OH

EXPLANATION: The oxygen-hydrogen bond in methanol is more polar due to smaller methyl group, leading to stronger hydrogen bonding as compared to ethanol.

(iii) Which compound is more soluble in water?                    

(a) C₂H₅OH                                     

(b) C₆H₅OH

(c) CH₃COCH₃                                

(d) n-Hexanol

ANSWER: (a) C₂H₅OH

EXPLANATION: Ethanol is more soluble in water due to greater extent of H-bonding as compared other molecules given in the options.

(iv) Which compound will have the maximum repulsion with H₂O?         

(a) C₆H₆                                          

(b) C₂H₅OH

(c) CH₃CH₂CH₂OH                          

(d) CH₃-O-CH₃

ANSWER: (a) C₆H₆

EXPLANATION: Being non-polar, benzene will have maximum repulsion with water which is a polar solvent.

(v) Ethanol can be converted into ethanoic acid by:

(a) Hydrogenation                            

(b) Hydration

(c) Oxidation                                  

(d) Fermentation

ANSWER: (c) Oxidation

EXPLANATION: C₂H₅OH + [O] ⟶ CH₃CHO + H₂O // CH₃CHO + [O] ⟶ CH₃COOH

(vi) Which enzyme is not involved in fermentation of starch? 

(a) Diastase                                     

(b) Zymase

(c) Urease                                       

(d) Invertase

ANSWER: (c) Urease

EXPLANATION: Urease is an enzyme that catalyzes the hydrolysis (breakdown) of urea into ammonia and carbon dioxide.

(vii) Which compound is called universal solvent?

(a) H₂O                                          

(b) CH₃OH

(c) C₂H₅OH                                     

(d) CH₃-O-CH₃

ANSWER: (a) H₂O

EXPLANATION: Water is regarded as the universal solvent because it can dissolve most of the ionic compounds as well as polar covalent compounds.

(viii) Methyl alcohol is not used:

(a) As a solvent

(b) As an anti-freezing agent

(c) As a substitute for petrol        

(d) For denaturing of ethyl alcohol

ANSWER: (c) As a substitute for petrol

EXPLANATION: Methyl alcohol is highly flammable, so it can be used as substitute for petrol or gasoline.

(ix) Rectified spirit contains alcohol about:    

(a) 80 %                       

(b) 85%                  

(c) 90%                  

(d) 95%

ANSWER: (d) 95%

EXPLANATION: Ethanol obtained by fermentation of molasses or starches is only upto 14% in water. It is then rectified or concentrated by distilling again and to reach 95% ethanol in 5% water. This 95% alcohol is called rectified spirit.

(x) According to Lewis concept ethers behave as:

(a) Acid                                          

(b) Base

(c) Acid as well as base                    

(d) None of them

ANSWER: (b) Base

EXPLANATION: Ethers behave as bases because they have lone pairs on O-atom, which can be donated to a proton or H⁺.