Match List-I with List-II.

List-I	List-II
(a) Sodium Carbonate	(i) Deacon
(b) Titanium	(ii) Castner-Kellner
(c) Chlorine	(iii) van-Arkel
(d) Sodium hydroxide	(iv) Solvay

Choose the correct answer from the options given below:

We need to match each substance with the correct industrial process.

(a) Sodium Carbonate is manufactured by the Solvay process (also called the ammonia soda process), which involves the reaction of sodium chloride, ammonia, and carbon dioxide. This matches (iv).

(b) Titanium of high purity is obtained by the van-Arkel method (also known as the crystal bar process), where crude titanium is converted to volatile $$TiI_4$$ which is then decomposed on a hot tungsten filament. This matches (iii).

(c) Chlorine is manufactured by the Deacon process, which involves the catalytic oxidation of HCl by atmospheric oxygen in the presence of $$CuCl_2$$ catalyst: $$4HCl + O_2 \xrightarrow{CuCl_2} 2Cl_2 + 2H_2O$$. This matches (i).

(d) Sodium hydroxide is produced by the Castner-Kellner process, which is an electrolytic process using a mercury cathode cell for the electrolysis of brine. This matches (ii).

The correct matching is (a)$$\to$$(iv), (b)$$\to$$(iii), (c)$$\to$$(i), (d)$$\to$$(ii), which is Option (4).