CH1012
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CRITICAL POINT
Critical point : if a substance in
a closed vessel is above its critical temperature (Tc) then it cannot be
liquefied by increasing p.
• At high p above Tc the substance exists as a supercritical fluid. (100’s atms).
This resembles a liquid but it has very different polarities to the
normal liquid phase.
eg. H2O(S.F.) non-polar solvent.
eg.
normally CO2 can be liquefied
easily by applying pressure .
easily by applying pressure .
above Tc = 310C this does not occur
& a supercritical fluid exists at > 75 atm.
& a supercritical fluid exists at > 75 atm.
CO2 (S.F.) is used to decaffinate coffee.
