The S - S bond energy is if Δ H f o E t - S - E t = - 147 kJ/mol; Δ H f o E t - S - S - E t = - 202 kJ/mol and Δ H f o S g = + 223 kJ/mol

Step-by-step solution

C 2 H 5 - S - C 2 H 5 + S s → C 2 H 5 - S - S - C 2 H 5 Δ H r e a c t i o n = Σ Δ H f p r o d u c t s o - Σ Δ H f reactants o = - 202 - - 147 = - 55 kJ Δ H reaction = Σ ( B E ) r e a c t i o n - Σ ( B E ) p r o d u c t s - 55 = Heat of sublimation or enthalpy of atomisation of sulphur - B E S - S - 55 = 223 - B E S - S B E ( S - S ) = 223 + 55 = 278 kJ