Which statement about chemical weathering is true?

• A. Chemical weathering reduces rock mass but not chemical changes.
• B. Chemical weathering proceeds by physical abrasion.
• C. Chemical weathering involves chemical reactions with water causing disintegration.
• D. Chemical weathering requires no water.

Answer: (C)

Chemical weathering changes minerals in rock through chemical reactions, usually in the presence of water. Water acts as both solvent and reactant, enabling processes like hydrolysis (where minerals react with water to form new minerals), dissolution (minerals dissolve into ions), and oxidation (often accelerated when water is involved). These chemical changes weaken the rock and can lead to disintegration over time, forming clay minerals and dissolved ions. That’s why the statement describing chemical weathering as involving chemical reactions with water that cause disintegration is the best choice. Mechanical abrasion or physical breakup happens in physical weathering, and water isn’t needed for all chemical reactions, but in most common scenarios chemical weathering is driven by reactions in water.