Tag: sedimentation, decantation and filtration

Sea water is a mixture. It contains water and dissolved minerals. Water and salt are compounds. Copper is element.

Sublimation is a technique that helps chemists to purify. During sublimation,upon heating, a solid substance is converted to the gas phase without passing through the liquid phase.  A solid is heated under vacuum. The solid volatilizes and condenses as a purified compound on a cooled surface,  a non-volatile residue of impurities is left behind.

Condensed solid produced during sublimation is sublimate. Thus, sublimate is a solid deposit of a substance which has sublimed.

Sublimation can be used to separate a mixture of solids in which one sublimes other does not. Thus, ammonium chloride can be separated from sodium chloride by sublimation. Ammonium chloride sublimes whereas sodium chloride does not.

The term sublimation refers to a physical change of state and is not used to describe transformation of a solid to a gas in a chemical reaction. The combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen.

Iodine is a chemical element with atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black metallic solid at a standard conditions that sublimes readily to form a violet gas.

Sublimation process is used to separate mixtures that contain a sublimate with a volatile component from a non-sublimate impurity. Thus, ammonium chloride can be separated from sodium chloride by sublimation. Ammonium chloride sublimes whereas sodium chloride does not.

The given statement is True.
 Method of separation by sublimation is limited. This method can be used for separation of only those compounds that sublime (i.e, change their state on heating from solid to vapour without passing through liquid state). Examples of sublimable compounds include iodine, ammonium chloride, camphor and naphthalene.

Note: If in the given mixture, none of the compounds is sublimable, then method of separation by sublimation cannot be used.

Ammonium chloride is separated from a mixture of sodium chloride and ammonium chloride by the process of sublimation. Ammonium chloride can be sublimed whereas sodium chloride cannot be sublimed. When a mixture of sodium chloride and ammonium chloride is heated, ammonium chloride changes its state from solid to vapour. The vapours of ammonium chloride are then condensed on cold surface. Sodium chloride is left behind.

Non reacting gases not reacted with each other so they only mix by diffusion.