In which of the following molecules/ions BF₃, NO$$_2^ - $$, NH$$_2^ - $$ and H₂O, the central atom is sp² hybridised?

The values of $$\Delta $$H and $$\Delta $$S for the reaction,

C_(graphite) + CO₂(g) $$ \to $$  2CO_(g)

are 170 kJ and 170 J K^$$-$$1, respectively. This reaction will be spontaneous at

From the following bond energies :
H $$-$$ H bond energy   : 431.37 kJ mol^$$-$$1
C $$=$$ C bond energy   : 606.10 kJ mol^$$-$$1
C $$-$$ C bond energy   : 336.49 kJ mol^$$-$$1
C $$-$$ H bond energy   : 410.50 kJ mol^$$-$$1
Enthalpy for the reaction,

will be

The dissociation constants for acetic acid and HCN at 25^oC are 1.5 $$ \times $$ 10^$$-$$5 and 4.5 $$ \times $$ 10^$$-$$10 respectively. The equilibrium constant for the equilibrium
CN^$$-$$ + CH₃COOH $$\rightleftharpoons$$ HCN + CH₃COO^$$-$$ would be