Sublimations are generally performed under reduced pressure because:

Sublimations are generally performed under reduced pressure
because: a. the attractive intermolecular interactions between the
molecules in the solid get weaker as the pressure is decreased. b. solids do not have a vapor pressure at atmospheric
pressure. c. less heat needs to be supplied for the vapor pressure of the
solid to equal that of the external pressure. d. solids do not melt when heated under reduced pressure. e. it prevents the pure product getting contaminated with
impurities in the air.

Sublimation occurs when a heated solid turns directly into a
gas, without an intervening liquid stage. Used as a method of
purification because the impurities found in most reaction mixtures
will not sublime easily. Vapors are made to condense on a cold
finger (a piece of glassware packed with dry ice or with cold water
running through it). To make a solid sublime, you must either raise
the temperature at low pressure or lower the pressure at a very
cold.
Role of the reduced pressure in the process is to reduce the
sublimation point of the substance since it depends on the system
pressure.
Correct option is :
c. less heat needs to be supplied for the vapor pressure of the
solid to equal that of the external pressure.

Leave a Comment