The correct order of the spin-only magnetic moments of the following complexes is :
(I) [Cr(H₂O)₆]Br₂
(II) Na₄[Fe(CN)₆]
(III) Na₃[Fe(C₂O₄)₃] ($$\Delta $$₀ $$>$$ P)
(IV) (Et₄N)₂[CoCl₄]

10.30 mg of O₂ is dissolved into a liter of sea water of density 1.03 g/mL. The concentration of O₂ in ppm is__________.

The sum of the total number of bonds between chromium and oxygen atoms in chromate and dichromate ions is ____________.

The number of sp² hybrid orbitals in a molecule of benzene is :