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91.

( +2) 2-methylbutan-1-ol (-) 2-methylbutan -1- ol have different values for which property?

  • Boiling point

  • Relative density

  • Refractive index

  • Specific rotation


D.

Specific rotation

( +) 2-methyl butan-1-ol and (-) 2-methyl butan-1-ol are enantiomer. Enantiomers are non-superimposable mirror images of each other hence, are optically active.

The optical activity of a compound can be confirmed by the value of specific rotation. It is defined as the rotation produced by solution of 10 cm length and unit concentration (1 g/ mL) for the given λ of light at the given temperature.


92.

375 mg of an alcohol reacts with required amount of methyl magnesium bromide and releases 140 mL of methane gas at STP. The alcohol is

  • ethanol

  • n-butanol

  • methanol

  • n-propanol


D.

n-propanol

The required reaction is

ROH375 mg + CH3MgBr  CH4140 mL at STP + Mg (OR)(Br)

Moles of CH4(n) at STP = 14022400 = 0.00625 moles

Here, -CH3 of CH3MgBr combines with H-atom of R-OH to give CH4.

 n(CH4) = n(R-OH)

Also, n = CnH2n+1.OH

Thus, 12n + 2n + 1 + 17 = 60  ( OH = 16 + 1 = 17)

 14n = 60 - 18 = 42

        n = 3

Hence, alcohol is n-propanol (C3H7OH).


93.

Phenol is a highly corrosive substance, but it 0.2 percent solution is used as

  • Antibiotic

  • Antiseptic

  • Disinfectant

  • Antihistamine


B.

Antiseptic

0.2% phenol solution is used as an antiseptic solution.


94.

The compound that would produce a nauseating smell/ odour with a hot mixture of chloroform and ethanolic potassium hydroxide is

  • PhCONH2

  • PhNHCH3

  • PhNH2

  • PhOH


C.

PhNH2

When primary amine reacts with chloroform and ethanolic potassium hydroxide, they produce isocyamides as main product. The reaction is also known as carbylamine reaction.

Ph-NH2 KOH (ethanolic)CHCl3(Nauseating smell) Ph.N → C


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95.

Reduction of the lactol S  OH with sodium borohydride gives


C.

The reaction occurs as follows:


96.

The main product (P) is

  • C6H5OC2H5

  • C2H5OC2H5

  • C6H5OC6H5

  • C6H5.I


B.

C2H5OC2H5

Since, C6H5O- is a weaker nucelophile than C2H5O-, therefore, the stronger nucleophile, i.e. C2H5O- will attack on C2H5I to give diethyl ether.

(i) C6H5OH + C2H5O- → C6H5O- + C2H5OH

(ii) C2H5O- + CH3.CH2.I → CH3CH2-O-CH2CH3


97.

Name of the following reaction is

  • Reimer-Tiemann

  • Kolbe-Schmitt

  • Cannizzaro

  • Gattermann


B.

Kolbe-Schmitt

The given reaction is known as Kolbe-Schmidt reaction. It is used to get salicylic acid.


98.

The order of reactivity of the following alcohols is

  • 1 > 2 > 3 > 4

  • 1 > 3 > 2 > 4

  • 4 > 3 > 2 > 1

  • 4 > 3 > 1 > 2


C.

4 > 3 > 2 > 1

The order of reactivity depends on the stability of the carbo cations of the respective species. The carbocations formed are

F.CH2.C+H.CH3, FCH2.CH2C+H.CH3

CH3.C+H.CHand Ph.C+H2

The stability order of carb-cation is 

PhC+H2 > CH3.C+H.CH3 > F.CH2.CH2.C+H.CH3 > F.CH2.CH2.C+H.CH3 > FCH2C+H.CH3

Hence, order of reactivity follows the order (4) > (3) > (2) > (1)


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99.

Which of the following compound (s) will give butanone on oxidation with alkaline KMnO4 solution?

  • Butan-1-ol

  • Butan-2-ol

  • Both (a) and (b)

  • None of the above


B.

Butan-2-ol

Alkaline KMnO4 is a strong oxidising agent. It oxidises primary alcohols to aldehyde and secondary alochols to ketones.

(i) CH3CH2CH2CH2(1°)-OH KMnO4 (alkl.)[O] CH3CH2CH2CH3Butanol

(ii) CH3CH2(2°)CH|OHCH3 KMnO4(alk.)[O] CH3CH2C||OCH3Butanone


100.

What are the organic products formed in the following reaction?

C6H5-COO-CH3 (ii)H2O(i) LiAlH4

  • C6H5-COOH and CH4

  • C6H5-CH2-OH and CH4

  • C6H5-CH3 and CH3-OH

  • C6H5-CH2-OH and CH3-OH


D.

C6H5-CH2-OH and CH3-OH


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