Before revision: Evidently, at this temperature, the two-component system has become a one-component system because both solid and liquid phases contains only the compound AB.Elements of Physical Chemistry, Puri-Sharma-PathaniaAtkins' Physical Chemistry 8th edition by Peter Atkins and Julio De Paula Phase Diagram for the Formation of a compound with congruent Melting PointCongruent melting point represents a definite temperature just like the melting points of pure components.
After revision: Evidently, at this temperature, the two-component system has become a one-component system because both solid and liquid phases contains only the compound AB.Elements of Physical Chemistry, Puri-Sharma-PathaniaAtkins' Physical Chemistry 8th edition by Peter Atkins and Julio De Paula Congruent melting point represents a definite temperature just like the melting points of pure components.