Which process is primarily used for the industrial production of quick lime (calcium oxide)?

The correct option is Heating limestone to decompose it.

Explanation

Quick lime (Calcium Oxide, CaO) is a widely used chemical compound produced industrially through the thermal decomposition of limestone (Calcium Carbonate, CaCO₃). This process is technically referred to as calcination.

Detailed Analysis:

• Heating limestone to decompose it is Correct: The standard industrial method involves heating limestone in a lime kiln to temperatures between 900°C and 1000°C. At these temperatures, calcium carbonate decomposes to form calcium oxide and carbon dioxide gas. The chemical equation is:
  CaCO₃ (s) $\xrightarrow{\Delta}$ CaO (s) + CO₂ (g)
  Since the reaction is reversible, the carbon dioxide produced is continuously removed to ensure the reaction proceeds in the forward direction to yield quick lime.
• Electrolysing aqueous calcium nitrate is Incorrect: Electrolysis of aqueous calcium nitrate would typically result in the evolution of hydrogen and oxygen gases or the formation of hydroxides, rather than the production of anhydrous calcium oxide.
• Reacting calcium hydroxide with carbon dioxide is Incorrect: The reaction of calcium hydroxide with carbon dioxide results in the formation of calcium carbonate (limestone) and water. This is the chemical basis for the "lime water turning milky" test, which is essentially the reverse of the lime production cycle.
• Displacing calcium from calcium chloride with sodium is Incorrect: Displacing calcium from calcium chloride using sodium is a metallothermic reduction process used to isolate calcium metal, not its oxide.

Key Takeaway:

Quick lime is manufactured by the thermal decomposition of limestone (calcium carbonate) at high temperatures, a process known as calcination.