Solved Exercise, Chem-12, Ch-11


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)

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)

Q.03: Multiple choice questions.

(i) Which compound shows hydrogen bonding?                

(a) C2H6                                          

(b) C2H5Cl

(c) CH3-O-CH3                                

(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

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

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

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


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

(a) Diastase                                     

(b) Zymase

(c) Urease                                       

(d) Invertase

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

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

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%

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

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

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