Part A As a technician in a large pharmaceutical research firm, you need to prod

Question

Part A

As a technician in a large pharmaceutical research firm, you need to produce 400. mL of a potassium dihydrogen phosphate buffer solution of pH = 6.98. The pKa of H2PO4 is 7.21.

You have the following supplies: 2.00 L of 1.00 M KH2PO4 stock solution, 1.50 L of 1.00 M K2HPO4 stock solution, and a carboy of pure distilled H2O.

How much 1.00 M KH2PO4 will you need to make this solution? (Assume additive volumes.)

Express your answer to three significant digits with the appropriate units.

Volume of KH2PO4 needed =

Part B

If the normal physiological concentration of HCO3 is 24 mM, what is the pH of blood if PCO2 drops to 23.0 mmHg ?

Express your answer numerically using two decimal places.

Explanation / Answer

pH = 6.98

pKa = 7.21

total volume of buffer = 400 mL

pH = pKa + log [HPO4- / H2PO4-]

6.98 = 7.21 + log [HPO4- / H2PO4-]

[HPO4- / H2PO4-] = 0.589

x / 400 - x = 0.589

x = 148 mL

volume of HPO4- = 148 mL

volume of KH2PO4 = 252 mL

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