Q.

The bond dissociation enthalpy of X2 ΔHbond calculated from the given data is _____ kJ mol-1. (Nearest integer)

M+X-(s)M+(g)+X-(g)     ΔHlattice=800 kJ mol-1

M(s)M(g)     ΔHsub=100kJ mol-1

M(g)M+(g)+e-(g)     ΔHi=500kJ mol-1

X(g)+e-(g)X-(g)     ΔHeg=-300kJ mol-1

M(s)+12X2(g)M+X-(s)     ΔHf=-400kJ mol-1

[Given: M+X- is a pure ionic compound and X forms a diatomic molecule X2 in gaseous state]                  [2025]


Ans.

(200)

ΔHf°=ΔHsub°+12ΔHbond°+ΔHi°+ΔHeg°-ΔHlattice°

-400=100+12ΔHbond°+500-300-800

ΔHbond°=200kJ/mol