The tendency of BF3, BCl3 and BBr3 to behave as Lewis acid decre

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 Multiple Choice QuestionsMultiple Choice Questions

291.

The alloy used in the contruction of aircrafts is :

  • Mg-Al

  • Mg-Mn

  • Mg-Zn

  • Mg-Sn


292.

Which of the following structure is similar to graphite? 

  • BN

  • B

  • B4

  • B4

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293.

The basic structural unit of silicates is 

  • SiO-

  • SiO24-

  • SiO32-

  • SiO32-

2598 Views

294.

Which of the following is electron deficient

  • (CH3)2

  • (SiH3)2

  • (BH3)2

  • (BH3)2

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295.

Name the type of the structure of silicates in which one oxygen atom of [SiO4]4- is shared?

  • Sheet silicate

  • Pyrosilicate

  • Three-dimensional silicate

  • Three-dimensional silicate

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296.

The tendency of BF3, BCl3 and BBr3 to behave as Lewis acid decreases in the sequence

  • BCl3 > BF3 > BBr3

  • BBr3 > BCl2 > BF3

  • BBr3 > BF3 > BCl3

  • BBr3 > BF3 > BCl3


B.

BBr3 > BCl2 > BF3

As the size of halogen atom increases, the acidic strength of boron halides increases. Thus, BF3 is the weakest Lewis acid. This is because of the pπ - pπ back bonding between the fully-filled unutilised 2p orbitals of F and vacant 2p orbitals of boron which makes BF3 less electron deficient. Such back donation is not possible in case of BCl3 or BBr3 due to the larger energy difference between their orbitals. Thus, these are more electron deficient. Since on moving are more electron deficient. Since on moving down the group the energy difference increases, Thus, the tendency to behave as Lewis acid follows the order

BBr3 > BCl3 > BF3

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297.

The correct regarding the electronegativity of hybrid orbitals of carbon is: 

  • sp> sp2<sp3

  • sp> sp2 > sp3

  • sp< sp2 > sp3

  • sp< sp2 > sp3

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298.

The correct order of atomic radii in group 13 elements is

  • B < Al < In < Ga < Tl

  • B < Al < Ga < In < Tl

  • B < Ga < Al < In < Tl

  • B < Ga < Al < Tl < In


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299.

In which of the following, the oxidation number of oxygen has been arranged in increasing order?

  • BaO2 < KO2 < O3 < OF2

  • OF2 < KO2 < BaO2 <O3

  • BaO2 < O3 < OF2 < KO2

  • KO2 < OF2 < O3 < BaO2


300.

The magnitude of screening effect depends upon the number of

  • inner electrons

  • outer electrons

  • bond order

  • Both (a) and (b)


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