Calculate the enthalpy of formation of sulphuric acid (l) from the following data :
(i) `S(s)+O_(2)(g) to SO_(2)(g),DeltaH=-71.0"kcal"`
(ii) `SO_(2)(g)+(1)/(2)O_(2)(g) to SO_(3)(g),DeltaH=-23.5"kcal"`
(iii) `SO_(3)(g)+H_(2)O(l) to H_(2)SO_(4)(l), DeltaH=-31.2 "kcal"`
(iv) `H_(2)(g)+(1)/(2)O_(2)(g) to H_(2)O(l),DeltaH=-68.5"kcal"`

Explanation

From the above equations, we have to calculate `DeltaH` for the equation
`H_(2)(g)+S(s)+2O_(2)(g) to H_(2)SO_(4)(l),DeltaH-=?`
Applying the inspection method,
[Eqn. (i)+Eqn. (ii) + Eqn. (iii)+Eqn.(iv)], we get,
`S(s)+O_(2)(g)+SO_(2)+(1)/(2)O_(2)(g)+SO_(3)(g)+H_(2)O(l)+H_(2)(g) to (1)/(2)O_(2)(g) to SO_(2)(g)+SO_(3)(g)+H_(2)SO_(4)(l)+H_(2)O(l), DeltaH=(-71.0-23.5-31.2-68.5) kcal
or `H_(2)(g)+S(s)+2O_(2)(g) to H_(2)SO_(4)(l),DeltaH=-194.2"kcal"`