Question

Out‌ ‌of‌ ‌sodium‌ ‌chloride‌ ‌($NaCl$)‌ ‌are‌ ‌methyl‌ ‌chloride‌ ‌($C{{H}_{3}}Cl$)‌ ‌which‌ ‌has‌ ‌higher‌ ‌melting‌ ‌and‌ ‌boiling‌ ‌point and Why?‌ ‌

Answer 1

The melting and boiling point of a compound depends on the bond strength possessed by the compound.
The ionic bonds are much stronger than the covalent bonds because of the coulombic attractions present between the constituent ions.

Complete step-by-step answer: The compounds which are made up by the ionic bond existing between them, are called ionic compounds, for example silver chloride. The ionic bonds are formed between two elements by donation and acceptance of electrons, meaning, one of the elements, which is silver in this case, donates its electron and the other element, chlorine in this case accepts it, it forms chloride ion. The compounds which have covalent bonds between them are called covalent compounds. The covalent bond is formed by sharing of electrons, from both the involved moieties.
Ionic bonds are known to have higher values of boiling and melting point, as compared to the covalent compounds.
Now if we consider the two molecules given in the question, out of which sodium chloride is an ionic compound and methyl chloride is a covalent one.
So, the compound sodium chloride would have higher melting and boiling point value because of its ionic nature, and consequently the methyl chloride would have lower values of the same.
This is because the strength in ionic bonds is much stronger, because of the attractions of opposite charges, as compared to covalent bonds, which occurs just by sharing the electrons, and so they take higher temperature to break.

Note: The sodium chloride being an ionic compound, has higher value of melting and boiling point, because the oppositely charged ions, as in sodium ion and chloride ion, have coulombic attractions present between them, which is much stronger than the covalent bond, where sharing takes place.