The difference in oxidation state of chromium in chromate and dichromate salts is ___________.

In the cobalt-carbonyl complex : [Co₂(CO)₈], number of Co-Co bonds is "X" and terminal CO ligands is "Y". X + Y = ___________.

A 0.166 g sample of an organic compound was digested with conc. H₂SO₄ and then distilled with NaOH. The ammonia gas evolved was passed through 50.0 mL of 0.5 N H₂SO₄. The used acid required 30.0 mL of 0.25 N NaOH for complete neutralization. The mass percentage of nitrogen in the organic compound is ____________.

Number of electrophilic centres in the given compound is _______________.