Question

Out of sodium chloride ($NaCl$) and methyl chloride ($C{H_3}Cl$), which has higher melting and boiling point? Why?

Answer 1

We need to understand the tendency of melting and boiling of the given compounds and compare between the two. Crystalline solids have a specific melting point which is the temperature at which the solid melts to become liquid. Boiling point is the temperature at which the liquid starts to boil and this temperature remains constant unless all of the liquid is converted into the gaseous phase. Different compounds have different melting and boiling points and we shall study and compare these properties of sodium chloride and methyl chloride.

Complete step by step answer:
We are to compare the melting and boiling points of sodium chloride ($NaCl$) and methyl chloride ($C{H_3}Cl$). Sodium chloride is a crystalline solid whereas methyl chloride is a gas which can be compressed to a liquid. Let us first study the factors affecting melting and boiling points of a substance. The most important factor that affects melting and boiling point of a substance is the type of bonding that occurs in the molecule.
$NaCl$ is an ionic compound containing ionic bonds between $N{a^ + }$ and $C{l^ - }$ . On the other hand, $C{H_3}Cl$ is a pure covalent compound and belongs to a class of haloalkanes hence it has covalent bonding. Ionic bonds result from the mutual attraction between oppositely charged ions and tend to be stronger than covalent bonds due to the coulombic attraction between ions of opposite charges. Due to this reason, sodium chloride ($NaCl$)has a higher melting and boiling point as compared to methyl chloride ($C{H_3}Cl$).

Note:
It must be noted that from the understanding of boiling and melting points, that methyl chloride will definitely have a lower melting and boiling point. In some cases where the methyl chloride is compressed to form liquid, it is easier to boil a liquid than a crystalline solid like sodium chloride. Sodium chloride being a solid will require more temperature to boil and melt and hence has a higher melting and boiling point.