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Weak Acid Dissociation Equation:
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The acid dissociation constant (Ka) quantifies the strength of a weak acid in solution, while pH measures the acidity or basicity of that solution. Understanding the relationship between pH and Ka is fundamental in acid-base chemistry.
The calculator uses the weak acid approximation formula:
Where:
Explanation: This calculation assumes the weak acid approximation, where the concentration of hydrogen ions is much smaller than the initial acid concentration.
Details: Ka values are crucial for understanding acid strength, predicting reaction outcomes, calculating pH of buffer solutions, and designing chemical processes in industrial and laboratory settings.
Tips: Enter pH value (0-14) and acid concentration in mol/L. Ensure pH values are within the valid range and concentrations are positive numbers.
Q1: What is the weak acid approximation?
A: The assumption that for weak acids, the hydrogen ion concentration is much smaller than the initial acid concentration, simplifying the calculation.
Q2: When is this approximation valid?
A: When Ka < 10⁻³ and the acid concentration is reasonably high (typically > 0.01 M).
Q3: What are typical Ka values for common acids?
A: Strong acids have Ka > 1, weak acids have Ka < 1. For example, acetic acid Ka ≈ 1.8×10⁻⁵, hydrochloric acid Ka ≈ 10⁷.
Q4: How does temperature affect Ka?
A: Ka values are temperature-dependent. Most acid dissociation constants change with temperature, though the effect is usually small near room temperature.
Q5: Can this calculator be used for polyprotic acids?
A: No, this calculator is designed for monoprotic weak acids. Polyprotic acids require more complex calculations considering multiple dissociation steps.