CBSE Class 12 Chemistry Alcohols Phenols And Ethers Worksheet Set 03

Assertion and Reason

Note: Read the Assertion (A) and Reason (R) carefully to mark the correct option out of the options given below:
a. If both assertion and reason are true and the reason is the correct explanation of the assertion.
b. If both assertion and reason are true but reason is not the correct explanation of the assertion.
c. If assertion is true but reason is false.
d. If the assertion and reason both are false.
e. If assertion is false but reason is true.

Question. Assertion: Lucas reagent is a mixture of anhydrous ZnCl₂ and concentrate HCl.
Reason: Primary alcohol produce ppt. with Lucas reagents.
Answer : C

Question. Assertion: Resorcinol turns FeCl₂ solution purple.
Reason: Resorcinol have phenolic group.
Answer : A

Question. Assertion: Phenol is more reactive than benzene towards electrophilic substitution reaction.
Reason: In the case of phenol, the intermediate carbocation is more resonance stabilized.
Answer : A

Question. Assertion: The ease of dehydration of alcohols follows the order. Primary > Secondary > Tertiary.
Reason: Dehydration proceeds through the formation of oxonium ions.
Answer : C

Question. Assertion: The major products formed by heating C₆H₂CH₂OCH₃ with HI are C₆H₅CH, I and CH₃OH.
Reason: Benzyl cation is more stable than methyl cation.
Answer : A

Question. Assertion: The pka of acetic acid is lower than that of phenol.
Reason: Phenoxide ion is more resonance stabilized.
Answer : C

Question. Assertion: Reimer-Tiemann reaction of phenol with CCl₄ in
NaOH at 340 K gives salicylic acis as the major product.
Reason: The reaction occurs through intermediate formation of dichlorocarbene.
Answer : C

Question. Assertion: Acid catalysed dehydration of t-butanol is slower than n-butanol.
Reason: Dehydration involves formation of the protonated alcohol, ROH₂⁺
Answer : C

Question. Assertion: Phenol undergo Kolbe reaction, ethanol does not.
Reason: Phenoxide ion is more basic than ethoxide ion.
Answer : C

Question. Assertion: Alcoholic fermentation involves conversion of sugar into ethyl alcohol by yeast.
Reason: Fermentation involves the slow decomposition of complex organic.
Answer : A

Question. Assertion: Tertiary alcohols give turbidity immediately with Lucas reagent.
Reason: A mixture of conc. HI + anhydrous ZnCl₂ is called Lucas reagent.
Answer : C

Question. Assertion: Both symmetrical and unsymmetrical ethers can be prepared by Williamson’s synthesis.
Reason: Williamson’s synthesis is an example of nucleophilic substitution reaction.
Answer : B

Question. Assertion: Phenol reacts with acyl halides in presence of pyridine to form phenyl acetate.
Reason: Benzoylation of phenol is carried out in the presence of NH₄OH.
Answer : C

Question. Assertion: Treatment of phenol with nitrous acid yields pbenzoquinone monoxime.
Reason: p-nitrosophenol and p-benzoquinone monoxime are tautomers.
Answer : B

Question. Assertion: (CH₃)₃ − Br and CH₃CH₂ ONa react to form (CH₃)₃ C −O−CH₂CH₃ .
Reason: Good yields of ethers are obtained when tertalkyl halides are treated with alkoxides.
Answer : D

Comprehension Based

Paragraph –I

The dehydration of alcohols and the conversion of alcohols to alkyl halides by treatment of hydrogen halides are similar in two important ways suggesting the formation of carbocation as key intermediate.
(a) Both reactions are protonated by acids.
(b) The reactivity of alcohols decrease in the order, tertiary > secondary>primary due to the formation of stable carbocations, which is stabilized by hyperconjugation and +I effect. The dehydration of alcohol follows three steps mechanism for acidbase catalysed dehydration of least stable tertiary butyl alcohol,

In step I, protonation (acid catalysed) of tert-butyl alcohol takes place. In step II, dissociation of tert-butyloxenium ion takes place followed by formation of carbocation. Alkene is formed in step III by deprotonation (base catalysed) of tert-butyl cation

Another important reaction of alcohols is iodoform reaction given by ethanol (in primary alcohols) and are secondary alcohols having 2-ol nature. Such alcohols give yellow ppt. of CHI₃ with NaOH and I₂ solution.

Question. Why dehydration of vinyl alcohol is not difficult?
a. Due to high enthalpy of vinylic —C—OH bond
b. Due to unstable nature of = C—OH bond by tautomerism
c. Carbocation never forms in case of vinyl alcohol
d. Both (a) and (b) are correct
Answer : D

Question. Which carbocation will not form an intermediate?

Answer : C

Question. Which will give iodoform test?
a. 2-methylpropan-2-ol
b. Ethyl acetoacetate
c. 2-methylbutan-2-ol
d. 3-methylpentant-2-ol
Answer : D

Question. The reagent used to distinguish 1-cycloethanol and 2-cycloethanol is:
a. soda lime
b. NaOH + H₂O
c. acidified KMnO₄
d. (aq.)FeCl₃
Answer : B

Question. An alcohol on iodoform reaction give iodoform and sodium salt of unsaturated acid containing 3 carbon atoms. The alcohol is:
a. but-3-en-2-ol
b. prop-2-en-2-ol
c. pent-3-en-2-ol
d. 3-methyl-but-3-en-2-ol
Answer : A

Match the Column

Question. Match the column

a.A→1; B→2; C→3; D→4; E→5
b. A→2; B→5; C→4; D→1; E→3
c. A→3; B→2; C→1; D→5; E→4
d. A→2; B→1; C→4; D→3; E→5
Answer : B

Question. Match the column.

a.A→1; B→2; C→3; D→5; E→4
b. A→4; B→3; C→2; D→1; E→5
c. A→3; B→2; C→1; D→4; E→5
d. A→2; B→3; C→4; D→5; E→1
Answer : D

Question. Match the column.

a.A→1; B→2; C→3; D→4; E→5
b. A→4; B→3; C→5; D→1; E→2
c. A→2; B→4; C→1; D→3; E→5
d. A→2; B→1; C→4; D→3; E→5
Answer : C

Integer

Question. The vapour density of C₂H₅OHis?
Answer : 23

Question. 10 gm of a mixture of hexane and ethanol reacts with sodium to give 200 ml. of H₂ at 27°C and 760 mm pressure.
The percentage of ethanol is?
Answer : 10

Question. Number of metamers represented by molecular formula C₄H₁₀O is:
Answer : 3

Question. What amount of bromine will be required to convert 2 g of phenol into 2, 4, 6-tribromophenol?
Answer : 10.22

Question. One mole of phenol reacts with bromine to form tribromophenol. How much bromine is used?
Answer : 3

Please click on below link to download CBSE Class 12 Chemistry Alcohols Phenols And Ethers Worksheet Set C