Which of the following combination will form an electrovalent bond ?

• P and Cl

• NH₃ and BF₃

• H and Ca

• H and S

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

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

• SO₂

• OH₂

• SH₂

• NH₃

The molecule which does not exhibit dipole moment is:

• NH₃

• CHCl₃

• H₂O

• CCl₄

Which of the following is isoelectronic with CO₂?

• NO₂

• NO

• N₂O

• N₂O₄

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

• methyl chloride

• iodoform

• chloroform

• carbon tetrachloride

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

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

• Acetone

• Acetic acid

• Acetonitrile

• Acetamide

The bond order of N${}_2^{+}$ is

• 1.5

• 3.0

• 2.5

• 2.0

320.

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

• SiF₄ and SF₄

• IO${}_3^{-}$ and XeO₃

• BH${}_4^{-} \mathrm{and} {\mathrm{NH}}_4^{+}$

• PF${}_6^{-}$ and SF₆