For the special case when T₀ and p₀ are the same as T_ref and p_ref, will be zero. The chemical exergy of pure CO at T₀, p₀where the reaction is given by

(3.134)

(3.135)

Water is present as a vapour within the environment, but normally is a liquid at T₀, p₀. The chemical exergy of liquid water is,

H2O(l) → H2O(g)

(3.136)

(3.137)

The specific exergy of a system is

(1.138)

and the specific flow exergy is given by

(3.139)

Between two states of system a constant composition, a_ch cancels, leaving just the thermo-mechanical contribution. For example, to find the chemical exergy of liquid octane, the reaction is

C8H18(l) + 12.5O2 → 8CO2 + 9H2O(g)

(3.140)

Assume the composition of the environment (on molar basis):
N₂ 75.67%, O₂ 20.35%, H₂O 3.12%, CO₂ 0.03% others 0.83%. Then,

(3.141)

Using the values given in Table 3.4,

(3.142)