a. Find the point e in Figure 13.29 and locate its corresponding location on Figure 13.30.
b. What phase(s) is (are) present at point e ?
c. Apply the Gibbs equilibrium phase rule to the system at this point.
d. What phase(s) is (are) present at point b in Figure 13.30?
e. If the temperature is raised slightly at point b , what phases will be present?
f. Apply the Gibbs equilibrium phase rule to the system at this slightly higher temperature.
a.
b. Ag_{(S)}, Ag_{2}O_{(S)} , O_2.
c. In Figure 13.29, the pressure is fixed. There is one reaction relating the three phases:
Ag_{(S)}+O_{2(G)}\leftrightarrow Ag_2O_{(S)}.
Thus,
F = C – R +1 – Φ
F = 3 – 1+1 – 3 = 0
The point e lies on an invariant temperature.
d. Ag_{(L)}, Ag_{2}O_{(S)} , O_{2(G)}
e. Ag_{(L)}, and O_{2(G)}.
f. F = C – R + 1 – Φ̣ = 3 – 1 + 1 – 2 = 1 (the temperature can change or the partial pressure of O_{2} can change and the state remains Ag_{(L)} and O_{2(G)}.
