In an octahedral structure, the pair of d orbitals involved in d²sp³-hybridisation is:

1. $d_{x^2-y^2},<mspace\; width="1em"></mspace>d_{z^2}$

2. $d_{xy},<mspace\; width="1em"></mspace>d_{x^2\mathit{-}{y}^{\mathit{2}}}$

3. $d_{{\mathrm{z}}^2},<mspace\; width="1em"></mspace>d_{xz}$

4. $d_{xy},<mspace\; width="1em"></mspace>d_{yz}$

The number of sigma bonds in P₄O₁₀ is 

1. 6

2. 16

3. 20

4. 7

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules?

1. Cl₂ > Br₂ > F₂ > I₂

2. Br₂ > I₂ > F₂ > Cl₂

3. F₂ > Cl₂ > Br₂ > I₂

4. I₂ > Br₂ > Cl₂ > F₂

Which one of the following molecules contain no $\mathrm{\pi }$ -bond?

1. CO₂

2. H₂O

3. SO₂

4. NO₂

The correct order of increasing bond length of 

C-H, C-O, C-C and C=C is:

1. C-C<C=C<C-O<C-H

2. C-O<C-H<C-C<C=C

3. C-H<C-O<C-C<C=C

4. C-H<C=C<C-O<C-C