Question:medium
When orthophosphoric acid is heated to 600$^{\circ}$C, the product formed is
When orthophosphoric acid is heated to 600$^{\circ}$C, the product formed is
Updated On: Jun 12, 2026
- $PH_3$
- $P_2O_5$
- $H_3PO_3$
- $HPO_3$
Show Solution
The Correct Option is D
Solution and Explanation
To determine the product formed when orthophosphoric acid is heated to 600°C, we need to understand the decomposition process of orthophosphoric acid (H_3PO_4) at high temperature.
Orthophosphoric acid can undergo dehydration under heating conditions to form different phosphoric acids depending on the temperature:
- At lower temperatures, H_3PO_4 may form pyrophosphoric acid (H_4P_2O_7).
- As the temperature increases, meta-phosphoric acid (HPO_3) is formed.
At around 600°C, the reaction is as follows:
H_3PO_4 \rightarrow HPO_3 + H_2O
The dehydration of orthophosphoric acid results in the formation of meta-phosphoric acid (HPO_3). Therefore, the correct product formed when orthophosphoric acid is heated to 600°C is meta-phosphoric acid.
Let's eliminate the other options based on this understanding:
- PH_3: Phosphine gas is not formed by simply heating orthophosphoric acid.
- P_2O_5: Phosphorus pentoxide is a further dehydration product at much higher temperatures than 600°C.
- H_3PO_3: This is phosphorous acid, not related to the heating of H_3PO_4 under these specific conditions.
Thus, the correct answer to the question is HPO_3.
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