Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Equilibrium
Acid-base equilibrium refers to the balance between the concentrations of acids and their conjugate bases in a solution. In the case of acetic acid, it partially dissociates in water to form acetate ions and hydrogen ions. The equilibrium constant, Ka, quantifies this dissociation, indicating the strength of the acid. Understanding this concept is crucial for calculating pH, as it directly relates to the concentration of hydrogen ions in the solution.
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Triprotic Acid Equilibrium
Concentration and Density
Concentration is a measure of how much solute is present in a given volume of solution, often expressed in terms of mass percent or molarity. In this question, the concentration of acetic acid is given as 3.50% by mass, which means 3.50 grams of acetic acid per 100 grams of solution. Density, defined as mass per unit volume, is used to convert mass percent into molarity, allowing for the calculation of the number of moles of acetic acid in a specific volume of vinegar.
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pH Calculation
pH is a logarithmic scale used to specify the acidity or basicity of a solution, calculated as the negative logarithm of the hydrogen ion concentration (pH = -log[H+]). To find the pH of vinegar, one must first determine the concentration of hydrogen ions produced from the dissociation of acetic acid. This involves using the Ka value and the initial concentration of acetic acid to find the equilibrium concentrations, which can then be used to calculate the pH.
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