Among the following, the pair in which the two species are not is

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 Multiple Choice QuestionsMultiple Choice Questions

311.

Which of the following combination will form an electrovalent bond ?

  • P and Cl

  • NH3 and BF3

  • H and Ca

  • H and S


312.

C-H bond energy is about 101 kcal/ mol for methane, ethane and other alkanes but is only 77 kcal/ mol for C-H bond of CH3 in toluene. This is because :

  • of inductive effect due to -CH3 in toluene

  • of the presence of benzene ring in toluene

  • of resonance among the structures of benzyl radical in toluene

  • aromaticity of toluene


313.

Which one of the following compounds has the smallest bond angle in its molecule ?

  • SO2

  • OH2

  • SH2

  • NH3


314.

The molecule which does not exhibit dipole moment is:

  • NH3

  • CHCl3

  • H2O

  • CCl4


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315.

Which of the following is isoelectronic with CO2?

  • NO2

  • NO

  • N2O

  • N2O4


316.

All bond angles are exactly equal to 109° 28' in:

  • methyl chloride

  • iodoform

  • chloroform

  • carbon tetrachloride


317.

The molecular shapes of SF4, CF4 and XeF4 are

  • different with 1, 0 and 2 lone pairs of electrons on the central atom, respectively

  • different with 0, 1 and 2 lone pairs of electrons on the central atom, respectively

  • the same with 1, 1 and 1 lone pair of electrons on the central atoms, respectively

  • the same with 2, 0 and 1 lone pairs of electrons on the central atom, respectively


318.

Which one of the following does not have sp2 hybridised carbon ?

  • Acetone

  • Acetic acid

  • Acetonitrile

  • Acetamide


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319.

The bond order of N2+ is

  • 1.5

  • 3.0

  • 2.5

  • 2.0


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320.

Among the following, the pair in which the two species are not isostructural, is

  • SiF4 and SF4

  • IO3- and XeO3

  • BH4- and NH4+

  • PF6- and SF6


A.

SiF4 and SF4

SiF4 and SF4 are not isostructural because SiF4 is tetrahedral due to sp3-hybridisation of Si.

14Si = 1s2, 2s2, 2p6, 3s2 3p2 (In ground state)

14Si = 1s2, 2s2, 2p6, 3s1 3p3 (In excited state)

Hence, four equivalent sp3-hybrid orbitals are obtained and they are overlapped by four
p-orbitals of four fluorine atoms on their axes. Thus, it shows following structure:

While SF4 is not tetrahedral but it is distorted tetrahedral because in it S is sp3d hybrid and has a lone pair of electron.

16S = 1s2, 2s2 2p6, 3s23px23py13pz1 (In ground state)

     = 1s2, 2s2 2p63s23px13py13pz1, 3dxy1sp3d hybridisation (In first excitation state)

Hence, sp3d hybrid orbitals are obtained. One orbital is already paired and rest four are overlapped with four p-orbitals of four fluorine atoms on their axes in trigonal bipyramidal form. This structure is distorted from trigonal bi-pyramidal to tetrahedral due to involvement of repulsion between lone pair and bond pair. 


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