Question 26 from UPSC CSE 2025 - Environme nt & Ecology

Question

Artificial way of causing rainfall to reduce air pollution makes use of

IASCODEX · Accepted Answer

Correct Option: A. silver iodide and potassium iodide

Strategy: Focus on the chemicals commonly associated with cloud seeding. Silver iodide is a classic agent used globally for artificial rainmaking. Potassium iodide is also a known nucleating agent, while silver nitrate and potassium nitrate are not conventionally used for this purpose. By identifying the standard pairing in practice (silver iodide with potassium iodide), one arrives at the correct option.

Key Info: Artificial rainfall, or cloud seeding, is a weather modification technique devised to induce precipitation in clouds, often to address drought or reduce air pollution. The typical agents used are silver iodide (AgI) and, less commonly, potassium iodide (KI). These compounds serve as ice nuclei, catalyzing the aggregation of water vapor into larger droplets that precipitate as rain. Silver iodide is preferred due to its similar crystalline structure to ice, which makes it effective at temperatures below freezing. Potassium iodide operates on a similar principle but is less commonly utilized. Silver nitrate, potassium nitrate, and potassium chloride are not standard cloud seeding agents due to ineffectiveness in mimicking ice crystal structures or lacking necessary nucleating properties. Internationally, cloud seeding has been adopted in various countries—including the United States, China, and India—as part of weather and pollution management strategies.

IASCODEX · Answer

Option B: silver nitrate and potassium iodide

IASCODEX · Answer

Option C: silver iodide and potassium nitrate

IASCODEX · Answer

Option D: silver nitrate and potassium chloride