AP Chemistry
8.7 pH and pKa
An acid-base indicator, \(\text{HIn}\), dissociates in aqueous solution according to the following equilibrium equation:
\[ \text{HIn(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{H}_3\text{O}^+\text{(aq)} + \text{In}^-\text{(aq)} \]
The indicator has a \(\text{p}K_a\) of \(4.2\). A student adds several drops of this indicator to a buffer solution maintained at a \(\text{pH}\) of \(6.5\). Which of the following correctly predicts the predominant form of the indicator in this solution and gives the correct justification?
\[ \text{HIn(aq)} + \text{H}_2\text{O(l)} \rightleftharpoons \text{H}_3\text{O}^+\text{(aq)} + \text{In}^-\text{(aq)} \]
The indicator has a \(\text{p}K_a\) of \(4.2\). A student adds several drops of this indicator to a buffer solution maintained at a \(\text{pH}\) of \(6.5\). Which of the following correctly predicts the predominant form of the indicator in this solution and gives the correct justification?
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