Question

Examples of sublimation does not include:
[A] Ammonium salts
[B] Nitrates
[C] Iodine
[D] Naphthalene

Answer 1

HINT: Sublimation is the process by which an element undergoes a phase transition from solid to vapour directly. Solids undergo sublimation at low pressure. However, there are few solids that undergo sublimation at atmospheric temperature and pressure.

COMPLETE STEP BY STEP SOLUTION: Before answering this question, let us discuss what sublimation is.
It is a phase transition where the element turns into a gas phase directly from the solid phase without actually passing through the liquid state. If we have a mixture of two elements among which one sublimes and one does not, we can separate the two by the process of sublimation.
Now, let us go through the options and find out whether they are examples of sublimation or not.
In the first option we have ammonium salts. Ammonium salt can be ammonium chloride, ammonium bromide etc. Ammonium chloride upon heating decomposes into ammonia and hydrogen chloride gas and it appears that it has undergone sublimation. We can write the reaction as-
\[N{{H}_{4}}Cl(s)\to N{{H}_{3}}(g)+HCl(g)\]
So we can say that it undergoes sublimation.
In the next option we have nitrates. Nitrates are compounds of nitrogen and oxygen and generally they do not undergo sublimation.
In the next option we have iodine. When we heat iodine slightly above the room temperature it does not turn into liquid. It undergoes phase transfer and is directly transferred into gaseous state from solid state. Therefore, it undergoes sublimation.
And lastly we have naphthalene. Naphthalene undergoes sublimation at room temperature. It is converted into vapour directly from the solid phase.
We can understand from the above discussion that nitrates do not undergo sublimation.

Therefore, the correct answer is option [B] Nitrates.


NOTE: Naphthalene and camphor undergo sublimation under normal condition of temperature and pressure. This is due to the fact that it is made up of non-polar molecules and the molecules in it are attracted by a weak intermolecular force, Van der Waals force. This causes efficient sublimation of naphthalene and camphor even without heating unlike iodine and ammonium chloride that needs to be heated to a certain temperature to undergo sublimation.