Q. Consider the following statements regarding phase equilibrium:

1. At the boiling point, liquid and vapor phases coexist.
2. At the melting point, solid and liquid phases coexist.
3. At the triple point, solid, liquid, and vapor phases coexist simultaneously.

Which of the above statements is / are correct?
Answer: 1, 2 and 3
Notes: All three statements accurately reflect principles of phase equilibrium. At a substance’s boiling point, liquid and vapor coexist; at the melting point, solid and liquid phases coexist. The triple point uniquely allows solid, liquid, and vapor phases to exist together under specific temperature and pressure, as seen for water at 0.01°C and 0.006 atm.