Question

Hydrolysis of P\(_4\)O\(_{10}\) produces a compound R, which on heating above 320°C yields a compound S. The compounds R and S, respectively, are

• A. H\(_3\)PO\(_4\) and (HPO\(_3\))\(_n\)
• B. H\(_3\)PO\(_4\) and (HPO\(_3\))\(_n\)
• C. H\(_3\)PO\(_4\) and H\(_4\)P\(_2\)O\(_7\)
• D. H\(_3\)PO\(_3\) and H\(_4\)P\(_2\)O\(_7\)

Hint:

Phosphoric acid (H\(_3\)PO\(_4\)) is the product of hydrolysis of P\(_4\)O\(_{10}\), and heating it leads to the formation of polyphosphoric acids (HPO\(_3\))\(_n\), a chain of phosphoric acid molecules.

Answer 1

The Correct Option is A

Step 1: Hydrolysis of P\(_4\)O\(_{10}\).
When phosphorus pentoxide (P\(_4\)O\(_{10}\)) reacts with water, it hydrolyzes to form phosphoric acid (H\(_3\)PO\(_4\)): \[ P_4O_{10} + 6 H_2O \rightarrow 4 H_3PO_4 \] Step 2: Heating above 320°C.
When phosphoric acid (H\(_3\)PO\(_4\)) is heated above 320°C, it undergoes dehydration to form polyphosphoric acids, which are a mixture of HPO\(_3\) and (HPO\(_3\))\(_n\) (i.e., chains of phosphoric acid molecules): \[ n H_3PO_4 \rightarrow (HPO_3)_n + (n-1) H_2O \] Step 3: Conclusion.
The correct compounds formed are H\(_3\)PO\(_4\) upon hydrolysis and (HPO\(_3\))\(_n\) upon heating above 320°C.
Final Answer: \[ \boxed{H_3PO_4 \text{ and } (HPO_3)_n} \]