AP Chemistry
8.9 Henderson-Hasselbalch Equation
A buffer solution at a physiological \(\text{pH}\) of \(7.40\) is prepared by mixing appropriate amounts of sodium dihydrogen phosphate, \(\text{NaH}_2\text{PO}_4\), and sodium hydrogen phosphate, \(\text{Na}_2\text{HPO}_4\). The acid-base equilibrium is represented by the equation below:
\[ \text{H}_2\text{PO}_4^-\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{HPO}_4^{2-}\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \text{p}K_a = 7.10 \]
Given that \(\log(2.0) \approx 0.30\), what is the required molar concentration ratio of \(\dfrac{[\text{HPO}_4^{2-}]}{[\text{H}_2\text{PO}_4^-]}\) in this buffer?
\[ \text{H}_2\text{PO}_4^-\text{(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{HPO}_4^{2-}\text{(aq)} + \text{H}_3\text{O}^+\text{(aq)} \quad \text{p}K_a = 7.10 \]
Given that \(\log(2.0) \approx 0.30\), what is the required molar concentration ratio of \(\dfrac{[\text{HPO}_4^{2-}]}{[\text{H}_2\text{PO}_4^-]}\) in this buffer?
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