521.

Which of the following has the highest bond order?

• N₂

• O₂

• He₂

• H₂

During the formation of a chemical bond

• electron-electron repulsion becomes more than the nucleus-electron attraction.

• energy of the system does not change.

• energy increases

• energy decreases

Which of the following is diamagnetic?

• H${}_2^{+}$

• O₂

• Li₂

• He${}_2^{+}$

In acetylene molecule, between the carbon atoms there are

• three pi bonds

• one sigma and two pi bonds

• two sigma and one pi bonds

• three sigma bonds

The number of nodal planes present in σ^* antibonding orbitals is

• 1

• 2

• 0

• 3

The overlapping of orbitals in benzene is of the type

• sp-sp

• p-p

• sp²-sp²

• sp³-sp³

The calculated bond order of superoxide ion ${\mathrm{O}}_2^{-} \mathrm{is}$

• 2.5

• 2

• 1.5

• 1

In the ionic equation

-BiO${}_3^{-}$ + 6H⁺ + xe^- → Bi³⁺ + 3H₂O , the value of x is

• 6

• 2

• 4

• 3

Mesomeric effect involves delocalisation of

• pi electrons

• sigma electron

• protons

• None of these

Angle strain in cyclopropane is

• 24°44'

• 9°44'

• 44'

• -5°16'