Question -
Answer -
Enthalpy change for a reaction (├ОтАЭH) is given by theexpression,
├ОтАЭH┬а= ├ОтАЭU┬а+ ├ОтАЭngRT
Where,
├ОтАЭU┬а= change in internalenergy
├ОтАЭng┬а= change in numberof moles
For the given reaction,
├ОтАЭng┬а= ├в╦ЖтАШng┬а(products) ├втВмтАЬ ├в╦ЖтАШng┬а(reactants)
= (2 ├втВмтАЬ 1.5) moles
├ОтАЭng┬а= 0.5 moles
And,
├ОтАЭU┬а= ├втВмтАЬ742.7 kJ mol├втВмтАЬ1
T┬а= 298 K
R = 8.314 ├ГтАФ 10├втВмтАЬ3┬аkJ mol├втВмтАЬ1┬аK├втВмтАЬ1
Substituting the values in the expression of├ОтАЭH:
├ОтАЭH┬а= (├втВмтАЬ742.7 kJ mol├втВмтАЬ1) + (0.5 mol) (298 K)(8.314 ├ГтАФ 10├втВмтАЬ3┬аkJ mol├втВмтАЬ1┬аK├втВмтАЬ1)
= ├втВмтАЬ742.7 + 1.2
├ОтАЭH┬а= ├втВмтАЬ741.5 kJ mol├втВмтАЬ1