Electric furnace (thermal) phosphorus route: In producing elemental white phosphorus from phosphate rock in an electric furnace, which additional materials are used?

Introduction / Context:
The thermal (electric furnace) process reduces phosphate rock to elemental phosphorus (P4). Understanding the required reactants clarifies stoichiometry and separates this route from acidulation processes that make fertilisers or phosphoric acid.

Given Data / Assumptions:

• Feed: phosphate rock (fluorapatite or related).
• High-temperature electric furnace operation.
• Goal: produce elemental white phosphorus.

Concept / Approach:
In the thermal process, silica (SiO2) acts as a flux to form calcium silicate slags, and coke (carbon) provides the reducing atmosphere that converts phosphate to phosphorus and CO/CO2. Sulphuric or phosphoric acids are not used in this high-temperature reduction route; those acids are relevant to wet-process phosphoric acid or superphosphate production, not to elemental phosphorus manufacture.

Step-by-Step Solution:

Verification / Alternative check:
Classical reaction set shows Ca3(PO4)2 + SiO2 + C → P4 (vapor) + Ca-silicate + CO/CO2.

Why Other Options Are Wrong:

• Phosphoric/sulphuric acid options refer to wet processes and superphosphate manufacture.
• Rock + coke only omits silica necessary for slag formation.
• Gypsum and air are not reagents in the thermal phosphorus route.

Common Pitfalls:
Mixing up thermal reduction (elemental P) with acidulation (fertiliser or H3PO4).

Final Answer:
Phosphate rock with silica and coke