Page 55 - Chemical equilibria Volume 4

the condition [2.17] is always satisfied because the molar fraction is always
less than 1. Properties of States of Physico-Chemical Equilibrium 31
On the other hand, if:

i ∑
ν < ν j [2.19]
j
The system evolves in the direction of consumption of the product added
only if condition [2.14] is satisfied. On the other hand, if condition [2.14] is
not fulfilled, the system reacts in the opposite direction, meaning that it
produces the component added.

This case is encountered during the synthesis of ammonia by the reaction:
N + 3H = 2NH 3 [2R.1]
2
2
because in this case, we have:
∑ ν =− 2
j
j
If we add hydrogen, the equilibrium always shifts to the right. However,
if we add nitrogen, the equilibrium shifts to the right only in the case where,
in the initial equilibrium state, according to relation [2.14], we have a molar
fraction of nitrogen less than 0.5.

Third case: if we have:
∑ ν > 0 [2.20]
j
j
– if the component added is a reagent, its algebraic stoichiometric number
is negative, and relation [2.14] leads to ℜ> if:
'0
ν
i < ∑ ν [2.21]
x k
i k
This condition is always satisfied because we have:

ν < 0 , x > and ∑ ν > 0
0
j
i
i
j