Calculate the [H₃O⁺] and pH of each polyprotic acid solution.
b. 0.125 M H₃C₆H₅O₇

검증된 단계별 안내

Identify that citric acid (H_3C_6H_5O_7) is a triprotic acid, meaning it can donate three protons (H^+).

Write the dissociation reactions for each step: \( \text{H}_3\text{C}_6\text{H}_5\text{O}_7 \rightleftharpoons \text{H}^+ + \text{H}_2\text{C}_6\text{H}_5\text{O}_7^- \), \( \text{H}_2\text{C}_6\text{H}_5\text{O}_7^- \rightleftharpoons \text{H}^+ + \text{HC}_6\text{H}_5\text{O}_7^{2-} \), and \( \text{HC}_6\text{H}_5\text{O}_7^{2-} \rightleftharpoons \text{H}^+ + \text{C}_6\text{H}_5\text{O}_7^{3-} \).

Use the first dissociation constant (\(K_{a1}\)) to calculate the initial [H_3O^+] concentration, assuming the first dissociation is the most significant.

Set up an ICE table (Initial, Change, Equilibrium) for the first dissociation to find the equilibrium concentrations of all species.

Calculate the pH using the formula \( \text{pH} = -\log[\text{H}_3\text{O}^+] \) once the [H_3O^+] is determined from the first dissociation.

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주요 개념

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Polyprotic Acids

Polyprotic acids are acids that can donate more than one proton (H+) per molecule in a solution. Each dissociation step has its own equilibrium constant, known as Ka, which decreases with each successive proton donation. Understanding the behavior of polyprotic acids is crucial for calculating the concentration of hydronium ions ([H3O+]) and the resulting pH in solutions.

Dissociation Constants (Ka)

The dissociation constant (Ka) quantifies the strength of an acid in solution, indicating how well it donates protons. For polyprotic acids, there are multiple Ka values corresponding to each dissociation step. These constants are essential for calculating the concentrations of ions in solution, particularly for determining the [H3O+] and pH of the acid solution.

pH Calculation

pH is a measure of the acidity of a solution, defined as the negative logarithm of the hydronium ion concentration: pH = -log[H3O+]. To calculate pH, one must first determine the [H3O+] from the dissociation of the acid, which may involve using the Ka values and the initial concentration of the acid. Understanding this relationship is key to solving the problem presented.

Calculate the [H3O+] and pH of each polyprotic acid solution.b. 0.125 M H3C6H5O7