Question

The total phosphate concentration in a blood sample is determined by spectrophotometry to be 3.0 x 10⁻M. If the pH of the blood sample is 7.45, what are the concentrations of H₂PO₄⁻ and HPO?

Answer 1

The individual concentrations of H2PO4− and HPO42− in blood at pH 7.45 cannot be determined without the equilibrium constant for the relevant dissociation of phosphoric acid or additional information.

Step-by-step explanation:

Understanding the concentration of phosphate species in blood involves applying principles of chemical equilibrium and the pH scale. In blood, phosphate exists mainly as H2PO4− and HPO42−. Given the blood pH of 7.45, we're in a region where H2PO4− and HPO42− coexist. However, without the equilibrium constant for the relevant dissociation of phosphoric acid at physiological temperature or additional context, we cannot calculate the individual concentrations of H2PO4− and HPO42− based solely on pH and total concentration. Normally, these concentrations would be determined using the Henderson-Hasselbalch equation for a buffer system, if the corresponding pKa value were known.