ANS:A - metaphosphoric acid

Sure, let's explain the possible outcomes:

1. Metaphosphoric acid: Metaphosphoric acid (HPO3), also known as polyphosphoric acid, is formed from orthophosphoric acid (H3PO4) by dehydration at high temperatures. It is a condensed form of phosphoric acid where the phosphate units are linked together by oxygen atoms in a linear chain. Metaphosphoric acid is commonly used in organic synthesis and as a dehydrating agent in chemical reactions.
2. Pyrophosphoric acid: Pyrophosphoric acid (H4P2O7) is also formed from orthophosphoric acid (H3PO4) by further condensation reactions at high temperatures, typically around 900°C. It is characterized by the presence of two phosphate units linked by an oxygen bridge. Pyrophosphoric acid is used in various industrial applications, including as a catalyst and a precursor for the production of other phosphorus compounds.
3. No change in it: If orthophosphoric acid (H3PO4) is heated but not to the temperature required for dehydration and condensation reactions, there will be no significant chemical change in the composition of the acid. Orthophosphoric acid will remain in its original form.

Considering the given temperature of about 900°C, the most likely outcome is the formation of pyrophosphoric acid through condensation reactions. At this temperature, orthophosphoric acid undergoes dehydration followed by condensation, leading to the formation of pyrophosphoric acid. Therefore, this is the most probable outcome. I hope this explanation clarifies the possible outcomes of heating orthophosphoric acid. Let me know if you need further assistance!