Question

Wax is an example of:
A. Ionic crystal
B. Covalent crystal
C. Molecular crystal
D. Metallic crystal

Answer 1

Hint: Crystalline solids are of four types which are given in the options. They are classified in the basis of their interaction between the atoms or molecules. We know that wax is an example of hydrocarbon which comes under the group of ester molecules.

Complete step by step answer:
Based on the type of interaction between the atoms or molecules, the properties of the solids may also differ. Wax is simply an ester molecule. It is of different types like paraffin wax, carnauba, beeswax etc. Since it is a type of hydrocarbon, it is classified as molecular solids. Major examples of molecular solids are organic compounds. They have different types of interaction like dipole-dipole interaction, hydrogen bonding, London forces etc. Some examples of molecules are ice, polyethylene, wax etc. Ice has hydrogen bonding, polyethylene has dispersion forces and wax has van der Waals forces. They are very soft so that they can be broken very easily. They have very less melting point. Wax also has a very less melting point. Sugar can also be included in molecular solids. Other solids are very strong and hard. But wax is very soft and thus included in molecular solids.
Thus wax is an example of molecular crystal.

Hence the correct option is C.

Additional information:
Ionic solids are generally very hard and they have very high melting points. Covalent solids are also very hard. The best example is diamond which is very strong.

Note:

Type of crystalline solids	Interaction	Examples
Ionic	Ionic bonding	${{NaCl,Ca}}{{{F}}_2},{{Hg}}$
Metallic	Metallic bonding	${{Na,Au,W,B}}$
Covalent	Covalent bonding	${{C,Si,}}{{{H}}_2},{{{I}}_2}$
Molecular	Hydrogen bonding, dipole-dipole, London dispersion	${{N}}{{{H}}_3},{{{H}}_2}{{O,C}}{{{O}}_2}$