Tag: sedimentation, decantation and filtration

Sublimation is the process in which a particular solid is converted into gas without changing into liquid. Naphthalene is volatile. It sublimates at room temperature without converting into liquid.

Sublimation is a specialized change of state when a solid substance skips the liquid phase and moves directly into the gas phase. This occurs because the substance absorbs energy so quickly from the surroundings that melting never occurs.

Salt dissolves in water. There is a high difference in their boiling point, so evaporation can be used to remove the water to obtain salt. The water vapours that evaporates can be condensed to form water. Salt is left behind as residue during evaporation.

Lead sulphate is insoluble in water whereas lead chloride is soluble. By dissolving the mixture of lead sulphate and lead chloride in water we can separate the two. After dissolving the mixture in water, lead sulphate can be obtained as the solid that's left behind. Lead chloride can be recovered by evaporating the solution.

By sublimation - Sulphur on heating directly converts into its gaseous state, which can later be converted into its solid state again. Carbon does not show the same property.

Iodine dissolved in alcohol is called tincture of iodine. Alcohol is a volatile liquid. So the mixture can be kept open or warmed in a water bath. Alcohol will evaporate leaving behind the iodine crystals.

There are way in separating mixtures of chloride salts such as that of sodium chloride and ammonium chloride. It can be done by crystallization, filtration, and sublimation. The easiest method among the three is separation by sublimation.  Ammonium chloride sublimes upon heating. Actually, the sublimation is a decomposition of ammonium chloride forming ammonia and hydrogen chloride. Sodium chloride, on the other hand, doesn't sublime and has a higher melting point than ammonium chloride. If we want to separate the mixture, we have to heat up to 330-350 degrees Celsius and collect the gas that will be produced. 

Hence, the correct option is D.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
To separate mixtures that contain a sublimate with volatile component from a non-sublimate impurity, the sublimation process is used. Ammonium chloride changes directly from solid to gaseous state on heating. The gaseous form of ammonium chloride can be cooled easily to get a pure solid.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. when heated iodine turns directly to vapours leaving behind the sand particles