Phosphoric acid family identification:\nThe condensed formula for metaphosphoric acid is ________.

Introduction / Context:
Orthophosphoric, pyrophosphoric, and metaphosphoric acids are central to phosphate chemistry and fertilizer processing. Recognizing their empirical formulas helps distinguish wet-process phosphoric acid streams, condensates, and polymerized species relevant to product quality and analysis.

Given Data / Assumptions:

• We compare common forms: ortho-, pyro-, and meta-.
• Question asks specifically for the formula of metaphosphoric acid.
• Condensed, text-friendly formulas are used instead of structural drawings.

Concept / Approach:
Orthophosphoric acid is H3PO4. Pyrophosphoric (diphosphoric) acid is H4P2O7, obtained by dehydration of two orthos. Metaphosphoric acid is represented by the repeating unit HPO3, commonly written as (HPO3)n for linear or cyclic polymers. Therefore, the “unit formula” that identifies metaphosphoric acid is HPO3.

Step-by-Step Solution:
Recall families: ortho = H3PO4; pyro = H4P2O7; meta = (HPO3)n.Condensed identification for meta uses the monomeric unit HPO3.Hence, select HPO3 for metaphosphoric acid.

Verification / Alternative check:
Reference tables list metaphosphoric acid as the polymeric series with empirical unit HPO3; analytical texts use this when describing dehydration and polymerization of orthophosphoric acid at elevated temperatures.

Why Other Options Are Wrong:
H3PO4 is ortho; H4P2O7 is pyro; “same as pyro” is incorrect; (H2PO2)2 corresponds to hypophosphorous acid chemistry, not metaphosphoric.

Common Pitfalls:
Confusing “pyro” with “meta” due to both involving dehydration; remember meta appears as a repeating HPO3 unit.

Final Answer:
HPO3