Give an example of each of such molecule having [2] i) polar co valent bond [0.5] ii) non polar covalent bond [0.5] iii) intermolecular hydrogen bond [0.5] iv) intramolecular hydrogen bond. [0.5]

i) Polar covalent bond: Water ($\mathrm{H}{}_2\mathrm{O}$) contains polar covalent bonds between oxygen and hydrogen atoms. Oxygen is highly electronegative (3.5) compared to hydrogen (2.1), creating an unequal sharing of electrons and a dipole moment.

ii) Non-polar covalent bond: Methane ($\mathrm{CH}{}_4$) exhibits non-polar covalent bonds. Carbon (2.5) and hydrogen (2.1) have similar electronegativities, resulting in equal electron sharing and no dipole moment.

iii) Intermolecular hydrogen bond: In liquid water, hydrogen bonds form between the hydrogen of one $\mathrm{H}{}_2\mathrm{O}$ molecule and the oxygen of another, linking molecules together.

iv) Intramolecular hydrogen bond: Salicylic acid ($\mathrm{C}{}_7\mathrm{H}{}_6\mathrm{O}{}_3$) shows intramolecular hydrogen bonding between the hydroxyl ($-\mathrm{OH}$) and carbonyl ($\mathrm{C}=\mathrm{O}$) groups within the same molecule. This stabilizes its structure.

Salicylic acidSalicylic acid