Identify the acid and the base from which sodium chloride is obtained. Which type of salt is it? When is it called rock salt? How is rock salt formed?

1. Acid and Base for Sodium Chloride ($NaCl$):

Sodium chloride is obtained from the neutralization reaction of:

• Acid: Hydrochloric acid ($HCl$)
• Base: Sodium hydroxide ($NaOH$)

$$\text{HCl}(aq) + \text{NaOH}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l)$$

2. Type of Salt:

It is a neutral salt because it is formed by the reaction of a strong acid ($HCl$) and a strong base ($NaOH$). Its aqueous solution has a pH of approximately $7$.

3. Rock Salt:

Common salt ($NaCl$) found in the form of large, brown-colored crystals due to the presence of impurities is called rock salt.

4. Formation of Rock Salt:

Rock salt was formed when seas of bygone ages dried up, leaving behind vast solid deposits of salt. These deposits are mined in a manner similar to coal mining.