The species in which the central atom uses sp² hybrid orbitals in its bonding is

Arrange the following :

N₂, O₂, F₂, Cl₂ in increasing order of bond dissociation energy

Write down the balanced equation for the reaction when:
Carbon dioxide is passed through a concentrated aqueous solution of sodium chloride saturated with ammonia.

The value of the expression $$\sqrt 3 \,\cos \,ec\,{20^0} - \sec \,{20^0}$$ is equal to