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GATE 2016 ME (ME3) – Question 27

Thermodynamics · Thermodynamic systems and processes, properties of pure substances · 1 mark · Multiple choice

The INCORRECT statement about the characteristics of critical point of a pure substance is that

  1. there is no constant temperature vaporization process
  2. it has point of inflection with zero slope
  3. the ice directly converts from solid phase to vapor phase
  4. saturated liquid and saturated vapor states are identical

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Show answer and explanation

Correct answer: (C) the ice directly converts from solid phase to vapor phase

Explanation

At a liquid–vapour critical point, the distinction between liquid and vapour disappears. Conversion of solid ice directly to vapour is sublimation, not a critical-point phenomenon. Therefore the incorrect statement is **C**. The phase path must be distinguished from the endpoint of liquid–vapour coexistence.