The correct option is KNO3.
Explanation
Saltpetre, historically known as Niter, is a naturally occurring mineral source of nitrogen. Chemically, it is an ionic salt that acts as a strong oxidizing agent, making it a critical component in the manufacture of gunpowder and fireworks.
- KNO3 is Correct: KNO3 represents Potassium Nitrate. It is commonly referred to as ‘Saltpetre’ or ‘Indian Saltpetre’. It is used in fireworks to provide oxygen for combustion and to produce violet-colored flames.
- NaCl is Incorrect: NaCl represents Sodium Chloride, which is widely known as common table salt.
- KCl is Incorrect: KCl represents Potassium Chloride. It is often used in fertilizers and as a sodium-free substitute for table salt.
- K2CO3 is Incorrect: K2CO3 represents Potassium Carbonate, historically known as Potash or Pearl Ash, used in glass and soap manufacturing.
Key Takeaway: The chemical formula for Saltpetre is KNO3 (Potassium Nitrate), which is distinct from Chile Saltpetre (NaNO3, Sodium Nitrate).