Among the following molecules / ions, $$C_2^{2 - },N_2^{2 - },O_2^{2 - },{O_2}$$ which one is diamagnetic and has the shortest bond length?

Which one of the following alkenes when treated with HCl yields majorly an anti Markovnikov product?

The ion that has sp³d² hybridization for the central atom, is :

For a reaction scheme $$A\buildrel {{k_1}} \over \longrightarrow B\buildrel {{k_2}} \over \longrightarrow C$$,

if the rate of formation of B is set to be zero then the concentration of B is given by :