Phosphate fertilizers: Triple superphosphate (TSP) is chemically represented by which principal compound?

Introduction / Context:
Single and triple superphosphates are produced by acidulating phosphate rock to yield water-soluble phosphate forms. Knowing the dominant chemical species helps in understanding nutrient availability and fertilizer quality specifications.

Given Data / Assumptions:

• TSP is made by reacting phosphate rock with phosphoric acid.
• End product should be largely water-soluble P2O5.
• The main calcium phosphate present is monocalcium phosphate.

Concept / Approach:
Triple superphosphate contains a high percentage of water-soluble phosphate as monocalcium phosphate, Ca(H2PO4)2. In contrast, unacidulated rock is principally tricalcium phosphate (insoluble), and single superphosphate contains a mixture including gypsum. Calcium metaphosphate or dicalcium phosphate do not represent the principal, intended soluble form in TSP fertilizer.

Step-by-Step Solution:

Verification / Alternative check:
Product specifications for TSP list high water-soluble P2O5, consistent with monocalcium phosphate content dominating the formulation.

Why Other Options Are Wrong:

• CaF2 · 3 Ca3(PO4)2 and 3 Ca3(PO4)2: components of raw rock (fluorapatite/tricalcium phosphate), largely insoluble.
• Ca(PO3)2 and CaHPO4: not the main compound in TSP; different solubility and usage.

Common Pitfalls:
Confusing single vs. triple superphosphate chemistries; remembering that “triple” indicates higher proportion of monocalcium phosphate from phosphoric acid digestion.

Final Answer:
Ca(H2PO4)2 (monocalcium phosphate).