To simulate the pH of blood, which is 7.4, an undergraduate researcher in a biology lab produced a buffer solution by dissolving sodium dihydrogen phosphate (K_a= 6.2 *10^-⁸) and disodium hydrogen phosphate (K_a= 3.6 *10^-¹³) together in an aqueous solution. What mole ratio of Na₂HPO₄/NaH₂PO₄ did she need to use?

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Quizplus · Accepted Answer

The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution: pH = pKa + log([A-]/[HA]). For the phosphate buffer system, pKa is approximately 7.2. To achieve a pH of 7.4, the ratio [A-]/[HA] should be slightly greater than 1, which corresponds to a ratio of approximately 1.6.

To Simulate the PH of Blood, Which Is 7