Change in H for
CO2 -->C+02?

−26.4 kcal

Explanation:

According to Hess's law, the total heat changes occuring during a chemical reaction are independent of path.

2CO(g)+O

2

(g)⟶2CO

2

(g)N ,

ΔH=−135.2 kcal

The above reaction is reversed and halved, we get-

CO

2

(g)⟶CO+

2

1

O

2

(g)

ΔH=

2

135.2

kcal (i)

C+O

2

(g)⟶CO

2

(g)

ΔH= -94 kcal ...(ii)

Required equation

C(s)+

2

1

O

2

(g)⟶CO(g);

Adding Eqs. (i) and (ii), we get

C(s)+

2

1

O

2

(g)⟶CO(g),

ΔH =

2

135.2

−94=−26.4 kcal