The S-S bond energy is if `DeltaH_(f)^(@)(E_(t)-S-E_(t))=-147kJ//mol,DeltaH_(f)^(@)(E_(t)-S-S-E_(t))=-202kJ//mol and DeltaH_(f)^(@)S(g)=+223 kJ//mol:`

Options

A. `168`kJ
B. 126 kJ
C. 278 kJ
D. 572 kJ

Answer

C

Explanation

`C_(2)H_(5)-S-C_(2)H_(5)+S(s)toC_(2)H_(5)-S-S-C_(2)H_(5)`
`DeltaH_("reaction")=sumDeltaH_(f("products"))^(@)-sumDeltaH_(f("reactants"))^(@)`
`=(-202)-(-147)=-55kJ`
`DeltaH_("reaction")=sumDeltaH_(f("reactants"))-sum(BE)_("products")`
`-55="heat of sublimation of enthalpy of atomisation of sulphur"-BE(S-S)` ltB rgt `BE(S-S)=223+55=278kJ`
(Common bonds of reactants and products are rejected.)