Question

In the following isobaric temperature–composition diagram, the number of common phases in all the invariant points is ________ (Answer in integer). 

Hint:

At constant pressure, invariant points in a binary system always involve 3 phases (F = 0).

Answer 1

Correct Answer: 2

Step 1: Understanding invariant points.
An invariant point is where three phase boundaries intersect under constant pressure, satisfying the phase rule \( F = C - P + 1 = 0 \).
Step 2: For binary systems (C = 2):
\( 0 = 2 - P + 1 \Rightarrow P = 3 \).
Step 3: Conclusion.
Each invariant point involves 3 phases.