Question

Which halogen can be purified by sublimation?
A. \[{{\text{F}}_2}\]
B. \[{\text{C}}{{\text{l}}_2}\]
C. \[{\text{B}}{{\text{r}}_2}\]
D. \[{{\text{I}}_2}\]

Answer 1

Hint: We know that, at room temperature, fluorine and chlorine are gases, bromine is a liquid and iodine is solid. Sublimation is the process, wherein the solid form of a substance is directly converted to gaseous form.

Complete step by step answer:
We know that, as we increase temperature of a substance, its vapour pressure increases. When this vapour pressure of a substance becomes more than the atmospheric pressure, the substance undergoes sublimation. The change of phase from solid to gas is called sublimation.
For a halogen to undergo this type of phase transition, it needs to be solid.
Iodine is solid at room temperature.
In the laboratory, solid iodine is kept in sublimation apparatus and is heated under vacuum. Because of the reduced pressure, the non-volatile impurities remain behind. Pure iodine volatilizes and settles on a cool surface by condensation.

Hence, option D is correct.

Additional information:
Iodine is dark purple in colour. It is highly electropositive non-metal. Even if being the least reactive element, it forms compounds with many other elements. It is found in nature in a water-soluble form known as brine. However, it is found on a large scale in the ocean in the form of minerals.

Note: We have to remember that a substance will undergo sublimation only when it is a solid. So, iodine is solid at room temperature and hence will undergo sublimation.