Wet-process phosphoric acid production chemistry In the wet process, phosphoric acid is produced by reacting phosphate rock with which reagent under controlled conditions?

Introduction / Context:
Phosphoric acid (H3PO4) is a critical intermediate for phosphate fertilizers. Industrially, the “wet process” digests phosphate rock with sulfuric acid to produce phosphoric acid and calcium sulfate by-products (gypsum or hemihydrate), after which clarifying and concentration steps follow.

Given Data / Assumptions:

• Feed: apatite-rich phosphate rock (typically fluorapatite).
• Operating conditions: controlled acid strength and temperature.
• Objective: maximize P2O5 recovery and manageable gypsum crystals.

Concept / Approach:
Using dilute sulfuric acid promotes conversion of the phosphate mineral to phosphoric acid while precipitating calcium as gypsum with suitable crystal habit for filtration. Too concentrated acid can hinder crystal growth and filtration. Nitric or hydrochloric routes exist for specialty processes (e.g., nitrophosphate), but the classic wet process uses dilute H2SO4.

Step-by-Step Solution:

Verification / Alternative check:
Process descriptions of dihydrate and hemihydrate routes emphasize sulfuric acid digestion at controlled dilution for optimum gypsum handling.

Why Other Options Are Wrong:

• Concentrated H2SO4: Poor filtration, side reactions.
• Concentrated HNO3 or HCl: Define different, less common pathways for bulk H3PO4 production.

Common Pitfalls:
Confusing wet-process acid (fertilizer grade) with purified thermal-process acid made by burning elemental phosphorus.

Final Answer:
dilute H2SO4 (sulfuric acid)