491.

The AsF₅ molecule is trigonal bipyramidal. The hybrid orbitals used by the As atoms for bonding are

• d_x²-y², d_z², s, p_x, p_y

• d_xy, s, p_x, p_y, p_z

• d_x²-y², s, p_x, p_y

• s, p_x, p_y, p_z, d_z²

Hydride of boron occurs as B₂H₆ but B₂Cl₆ does not exist. This is because

• p$\mathrm{\pi }$ - d$\mathrm{\pi }$ back bonding is possible in B₂H₆ but not in B₂Cl₆

• boron and hydrogen have almost equal values of electronegativity

• boron and chlorine have almost equal atomic sizes

• small hydrogen atoms can easily fit in between boron atoms but large chlorine atoms do not.

Assertion : trans-Pent-2-ene is polar but trans- but-2-ene is non-polar.

Reason : The polarity of cis-isomer is more than trans-isomer, which are either non-polar or less polar.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false

Assertion : The number of tetrahedral voids is double the number of octahedral voids.

Reason : The size of the tetrahedral voids is half of that of the octahedral void.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion : [Fe(CN)₆]^3- has d²sp³ type hybridisation.

Reason: [Fe(CN)₆]^3- ion shows magnetic moment corresponding to two unpaired electrons.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion: Both $\mathrm{\pi }$(2p_x) and $\mathrm{\pi }$^*(2p_x) MO's have one nodal plane.

Reason : All MO's formed by side way overlapping of 2p- orbitals have one nodal plane.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

Which of the following molecules has more than one lone pair ?

• SO₂

• XeF₂

• SiF₄

• CH₄

Each NH₃ molecule has six other NH₃ molecules as nearest neighbours in solid state ; $∆$H of sublimation of NH₃ molecule at the m.p. is 30.8 kJ mol^-1 and in the absence of H-bonding estimated Ml of sublimation is 14.4 kJ mol^-1 .Hence , strength of H-bond in solid NH₃ is :

• 5.47 kJ mol^-1

• 10.93 kJ mol^-1

• 16.40 kJ mol^-1

• - 16.40 kJ mol^-1

Four diatomic species are listed below in different sequences. Which of these represents the correct order of their increasing bond order?

• ${\mathrm{C}}_2^{2-}$ < ${\mathrm{He}}_2^{+}$ < NO < ${\mathrm{O}}_2^{-}$

• ${\mathrm{He}}_2^{+}$ < ${\mathrm{O}}_2^{-}$ < NO < ${\mathrm{C}}_2^{2-}$

• ${\mathrm{O}}_2^{-}$ < NO < ${\mathrm{C}}_2^{2-}$ < ${\mathrm{He}}_2^{+}$

• NO < ${\mathrm{C}}_2^{2-}$ < ${\mathrm{O}}_2^{-}$ < ${\mathrm{He}}_2^{+}$

Which one ofthe following is not tetrahedral in shape ?

• SiCl₄

• N${\mathrm{H}}_4^{+}$

• CH₄

• SF₄