Lime's Dual Effect on Soil pH and Fertilizer Availability

Steps:

• Calcium hydroxide (Ca(OH)₂) dissociates to release OH⁻ ions, neutralizing H⁺ in acidic soil via Ca(OH)₂ + 2H⁺ → Ca²⁺ + 2H₂O (equation 2).
• This raises soil pH, reducing acidity as intended.
• At higher pH, ammonium fertilizers (NH₄⁺) convert to volatile NH₃ gas via 2NH₄⁺ + Ca(OH)₂ → Ca²⁺ + 2NH₃↑ + 2H₂O (equation 3), causing nitrogen loss.
• Equations 2 and 3 together explain both the acidity reduction and fertilizer inefficiency.

Why C is correct:

• Option C pairs equation 2 (pH neutralization) with equation 3 (ammonia volatilization from fertilizers), directly linking lime's benefits and drawbacks per acid-base chemistry principles.

Why the others are wrong:

• A includes irrelevant equations not tied to pH or nutrient loss.
• B mixes neutralization with unrelated phosphate precipitation, missing nitrogen loss.
• D focuses only on precipitation reactions, ignoring acidity reduction.

Final answer: C