Question

The form of phosphorus in rock phosphate is:

• A. Ca(H$_2$PO$_4$)$_2$
• B. CaHPO$_4$
• C. Ca$_3$(PO$_4$)$_2$
• D. 3(Ca$_3$(PO$_4$)$_2$)·Ca(OH)$_2$

Hint:

Rock phosphate primarily contains insoluble tricalcium phosphate, which is processed into soluble forms for agricultural use.

Answer 1

The Correct Option is D

Step 1: Rock phosphate is a naturally occurring apatite mineral, not a refined salt.
Step 2: Options 1 and 2 are acid-treated, soluble fertiliser forms, not the raw mineral.
Step 3: \( \text{Ca}_3(\text{PO}_4)_2 \) alone ignores the hydroxide component of the natural apatite lattice.
Step 4: The correct answer is \[ \boxed{3(\text{Ca}_3(\text{PO}_4)_2)\cdot\text{Ca(OH)}_2} \]