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JEE Main levelSingle correct optionDifficulty 2 of 3rg040

Which statement about the critical point of a pure substance is correct?

  1. AAt the critical point the densities of liquid and gas phases become equal
  2. BAt the critical point the surface tension of the liquid is maximum
  3. CAbove the critical point distinct liquid and gas phases coexist
  4. DAt the critical point is positive

Answer: A

At the critical point the meniscus between liquid and vapour disappears because the two phases become identical in density and all other properties. Surface tension falls to zero there, no two phases coexist above , and the isotherm has a horizontal inflection with .
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