ANS:A - K₂O

The promoter used in NH3 synthesis catalyst is typically K2O (potassium oxide). Potassium oxide (K2O) is commonly used as a promoter in the catalyst for the synthesis of ammonia (NH3) via the Haber-Bosch process. The addition of potassium oxide to the iron-based catalyst helps improve its catalytic activity and selectivity, leading to higher ammonia yields and improved reaction kinetics. So, the correct option is: K2O Potassium oxide (K2O) is a chemical compound composed of potassium (K) and oxygen (O) ions in a 1:1 ratio. It is an oxide of potassium and is commonly referred to as potash. Potassium oxide is a white, crystalline solid that is highly reactive and readily forms potassium hydroxide (KOH) when exposed to water. Here are some key points about potassium oxide (K2O):

1. Chemical Properties: Potassium oxide is a basic oxide, meaning it reacts with water to form a strongly alkaline solution of potassium hydroxide. The reaction between potassium oxide and water is exothermic and produces a significant amount of heat. The chemical equation for this reaction is: 𝐾2𝑂(𝑠)+𝐻2𝑂(𝑙)→2𝐾𝑂𝐻(𝑎𝑞)K2​O(s)+H2​O(l)→2KOH(aq)
2. Applications:
   • Agriculture: Potassium oxide is an essential nutrient for plant growth and is commonly used as a fertilizer to replenish potassium levels in soils. Potassium is important for various physiological processes in plants, including enzyme activation, osmoregulation, and nutrient transport.
   • Industry: Potassium oxide has applications in various industrial processes, including glass manufacturing, where it is used as a flux to lower the melting point of silica and improve the flow properties of molten glass. It is also used in the production of specialty ceramics, catalysts, and other chemical compounds.
   • Chemical Synthesis: Potassium oxide can be used as a reagent in chemical synthesis reactions to introduce potassium ions into organic and inorganic compounds. It can also serve as a source of potassium in the synthesis of other potassium compounds.
   • Desiccant: Potassium oxide is sometimes used as a desiccant (drying agent) to absorb moisture from air or gases due to its strong affinity for water.
3. Safety Considerations: Potassium oxide is highly reactive with water and strong acids, and it can cause severe burns upon contact with skin, eyes, or mucous membranes. It should be handled with care, and appropriate safety precautions should be taken to prevent accidental exposure.