Among the following, the energy of 2s orbital is lowest in :

The coordination numbers of Co and Al in [Co(Cl)(en)₂]Cl and K₃[Al(C₂O₄)₃], respectively, are : (en = ethane-1, 2-diamine)

25 g of an unknown hydrocarbon upon burning produces 88 g of CO₂ and 9 g of H₂O. This unknown hydrocarbon contains :

Thermal decomposition of a Mn compound (X) at 513 K results in compound Y, MnO₂ and gaseous product. MnO₂ reacts with NaCl and concentrated H₂O₄ to give a pungent gas Z. X, Y and Z, respectively, are :