A biochemical reaction takes place in a 1.00 ml solution of 0.0250 M phosphate buffer initially at pH = 7.20 (see Table 2.6 for pK_as of phosphate species). 

(a) Are the concentrations of any of the four possible phosphate species negligible? If so, identify them and explain your answer. 

(b) During the reaction, 3.80 чmol of HCl are produced. Calculate the final pH of the reaction solution. Assume that the HCl is completely neutralized by the buffer.

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TABLE 2.6 Some weak acids and their conjugate bases Acid (Proton Donor) HCOOH Formic acid CH₂COOH Acetic acid OH 1 CH₂CH-COOH Lactic acid H₂PO4 Phosphoric acid H₂PO4 Dihydrogen phosphate ion HPO Monohydrogen phosphate ion HCO, Carbonic acid HCO₂ Bicarbonate ion C₂H5OH Phenol NH₂ Ammonium ion Conjugate Base (Proton Acceptor) HCOO Formate ion CH₂COO Acetate ion OH 1 CH₂CH-COO™ Lactate ion H₂PO₂ Dihydrogen phosphate ion HPO,² Monohydrogen phosphate ion PO Phosphate ion HCO₂ Bicarbonate ion co₂²- Carbonate ion C₂H₂O Phenolate ion NH₂ Ammonia +H+ +H* +H* +H+ +H* +H+ +H+ +H+ +H* +H+ pk₂ 3.75 4.76 3.86 2.14 6.86 12.4 6.3* 10.25 9.89 9.25 K₂ (M) 1.78 x 10-4 1.74 x 10-5 1.38 x 10-4 7.24 x 10-3 1.38 x 107 3.98 x 10-13 5.1 x 107 5.62 x 10-11 1.29 x 10-10 5.62 x 10 10