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 Multiple Choice QuestionsMultiple Choice Questions

21.

When ethyl alcohol is heated with conc. H2SO4, the product obtained is

  • CH3COOC2H5

  • C2H2

  • C2H6

  • C2H4


D.

C2H4

When ethyl alcohol is heated with conc H2SO4 at 160°- 170°C, the product obtained is ethylene (C2H4).

CH3-CH2OH + H2SO4  CH3CH2HSO4 + H2ethyl hydrogen sulphateOCH3CH2HSO4 160- 170 °C CH2=CH2ethylene + H2SO4 but at lower temperature ether is formed. 


22.

Williamson's synthesis involves

  • SN1 mechanism

  • nucleophilic addition

  • SN2 mechanism

  • SE mechanism


C.

SN2 mechanism

When sodium or potassium alkoxide is heated with an alkyl halide to give ether, this reaction is known as Williamson's synthesis.

 RONa + R'X  R-O-R' + NaX

This is an example of nucleophilic substitution and follow SN2 mechanism.


23.

In the reaction

2A + drysilver oxide  ether + 2AgX     A is a/an

  • primary alcohol

  • acid

  • alkyl halide

  • alcohol


C.

alkyl halide

An alkyl halide on heating with dry silver oxide gives ether.

2R-Xalkylhalide + Ag2O dry R - O- R ether+ 2AgX


24.

  is the anhydride of 

  • 1, 2-butane diol

  • 2, 2-butane diol

  • 2, 3-butane diol

  • 1, 1-butane diol


C.

2, 3-butane diol

Hence,  is the anhydride of 2, 3-butane diol.


25.

Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid,gives 

  • 2,4,6-trinitrobenzene

  • o-nitrophenol

  • p-nitrophenol

  • p-nitrophenol


B.

o-nitrophenol

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26.

1-chlorobutane on reaction with alcholic potash gives

  • but-1-ene

  • butan-1-ol

  • but-2-ene

  • butan-2-ol


A.

but-1-ene

CH3-CH2-CH2-CH2-Cl1-chlorobutane  alco, KOH CH3-CH2-CH=CH2butene-1 +HCl


27.

Following reaction

(CH3)3CBr + H2O  (CH3)3C-OH + HBr is an example of

  • elimination reaction

  • free radical substitution

  • nucleophilic substitution

  • electrophilic substitution


C.

nucleophilic substitution

(CH3)3CBr + H2O  (CH3)3C-OH + HBr

Br is substituted by OH- (nucleophile).
SN1 (unimolecular substitution reaction).


28.

Hydroboration oxidation of 4-methyl octene would give

  • 4-methyl octanol

  • 2-methyl decane

  • 4-methyl heptanol

  • 4-methyl-2-octanone


A.

4-methyl octanol

Terminal alkenes react rapidly with diborane to form primary trialkyl boranes which on oxidation gives primary alcohols.

               

(In general hydroboration oxidation involve the addition of water according to anti-Markownikoff's rule).

 


29.

The number of isomeric ethers with molecular formula C4H10O is / are

  • one

  • two

  • three

  • four


A.

one

C.

three

Isomers of C4H10O are follows

(i) H3C-CH2-CH2-OHbutanol-1(ii) H3C-CHOH-CH2-CH3butanol-2(iii) CH3-CH(CH3)-CH2-OH2-methyl propanol-1

(iv) 

(v) H3C-CH2-O-CH2-CH3diethyl ether(vi) H3C-O-CH<CH3CH3methyl isopropyl ether

(vii)

Hence, three isomeric ethers are possible.


30.

Anisole is the product obtained from phenol by the reaction known as

  • coupling

  • etherification

  • oxidation

  • esterification


B.

etherification

In presence of NaOH or KOH, phenol reacts with alkyl halide and gives phenolic ether (C6H5OR).

C6H5OH + NaOH -H2O C6H5O- Na -NaXRX C6H5 -O-RVapour of C6H5OH  and CH3OH, with red hot ThO2(thoria) give anisole (phenolic ether).C6H5OH + CH3OH ThO2 C6H5OCH3 + H2O