$(a)$ 'Sodium is a highly reactive metal and it cannot be obtained from its oxide by heating with carbon'. Give reason.
$(b)$ How can sodium be obtained from sodium chloride?

(N/A) Sodium is a highly reactive metal with a very high affinity for oxygen. Carbon is a weaker reducing agent than sodium,so it cannot reduce sodium oxide to sodium metal.
$(b)$ Sodium is obtained from molten sodium chloride $(NaCl)$ by the process of electrolytic reduction (electrolysis). During this process,sodium ions $(Na^+)$ are reduced at the cathode to form metallic sodium $(Na)$.