The answer is each indicator has a narrow range. We need many different indicators to span the entire ph spectrum because each indicator has a narrow range.
I really don’t know but
Phosphorus pentoxide is a white solid which does not have any distinct odour. The chemical formula of this compound is P4O10. However, it is named after its empirical formula, which is P2O5. The molar mass of phosphorus pentoxide corresponds to 283.9 g/mol.
