The correct option is 1 and 3 only.
Explanation
Chemical weathering refers to a group of weathering processes-such as solution, carbonation, hydration, oxidation, and reduction-that act on rocks to decompose, dissolve, or reduce them through chemical reactions.
- Statement 1 is correct: Chemical weathering processes, specifically solution and carbonation, act on rocks to decompose, dissolve, or reduce them to a fine clastic state. This transformation occurs through chemical reactions driven by oxygen, surface or soil water, and other acids.
- Statement 2 is incorrect: Water and air (specifically oxygen and carbon dioxide) are the primary agents that accelerate chemical reactions. They do not retard them. Water acts as a solvent and a medium for reactions, while oxygen and carbon dioxide are essential reactants in oxidation and carbonation processes.
- Statement 3 is correct: The decomposition of organic matter (plants and animals) releases carbon dioxide. This significantly increases the quantity of carbon dioxide underground (in soil air), often making it much higher than atmospheric levels. This elevated CO2 concentration enhances the carbonation process by forming carbonic acid when mixed with soil water.
Key Takeaway: Chemical weathering relies on water and atmospheric gases to decompose rocks into finer materials. Biological decomposition accelerates this by increasing the concentration of underground carbon dioxide, thereby intensifying chemical reactions.