The molal freezing point depression constant for benzene (C6H6) i

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 Multiple Choice QuestionsMultiple Choice Questions

221.

The major product P will be


222.

The product P of the given reaction is 

 


223.

In the reaction 

C7H3Cl2/  X Br2/ Fe Y Zn/ HCl Z

Z is

  • o-bromotoluene

  • m-bromotoluene

  • p-bromotoluene

  • 3-bromo-2, 2, 6- trichlorotoluene


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224.

The molal freezing point depression constant for benzene (C6H6) is 4.90 K Kg mol-1. Selenium exists as a polymer of the type Sex. When 3.26 g of selenium is dissolved in 226 g of benzene, the observed freezing point is 0.112°C lower than that of pure benzene. The molecular formula of selenium is (atomic mass of Se = 78.8 g mol-1).

  • Se8

  • Se6

  • Se4

  • Se2


A.

Se8

To calculate the molar mass of Selenium (Se)

MB = Kf ×WBTf × WA

Mass of Selenium (WB) = 3.26 gm

Mass of Benzene (WA) = 226 gm = 0.226 kg

Depression in freezing point (Tf) = 0.112°C

Molar depression constant (Kf) = 4.9K kg mol-1

MB = (4.9 kg mol-1) (3.26 gm)(0.112 K) (0.226 kg) = 631.08 g mol-1

Given, gram atomic mass of selenium = 78.8 g/mol

For Sex (78.8 g mol-1) = 631.08 g mol-1

or, x = 631.08 g mol-178.8 g mol-1 = 8

Thus, molecular formula of selenium = Se8


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225.

X, Y and Z respectively are


226.

Choose the correct alkyne and reagents for the preparation of

 


227.

For carbanion

Stability order will be

  • P > Q > S > R

  • P > R > Q > S

  • Q > R > S > R

  • S > R > Q > P


228.

Which one of the following acts as a nucleophile?

  • (CH3)3N

  • BF3

  • N+O2

  • CH3 - C+ = O


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229.

Which of the following compounds have highest melting point?

  • Only I

  • Only II

  • I and II

  • II and III


230.

Identify the major product 'X' obtained in the following reaction.

2, 3-dimethyl butan-2-ol conc. H2SO4 X


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