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pH Formula for Weak Acid:
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The pH calculation formula for weak acids estimates the acidity of a solution based on the acid dissociation constant (Ka) and the concentration of the acid. This formula provides a simplified approach for calculating pH when dealing with weak acids that don't completely dissociate in solution.
The calculator uses the pH formula for weak acids:
Where:
Explanation: The formula calculates the negative logarithm of the square root of the product of the acid dissociation constant and the acid concentration, providing the pH value of the solution.
Details: Accurate pH calculation is crucial for understanding acid-base chemistry, predicting chemical behavior, and applications in various fields including biochemistry, environmental science, and industrial processes.
Tips: Enter the acid dissociation constant (Ka) in mol/L and the concentration (C) in mol/L. Both values must be positive numbers greater than zero for accurate calculation.
Q1: When is this formula applicable?
A: This formula is specifically designed for weak acids where the approximation [H⁺] = √(Ka × C) is valid, typically when Ka is small and concentration is not extremely dilute.
Q2: What are typical Ka values for weak acids?
A: Weak acids typically have Ka values ranging from 10⁻² to 10⁻¹⁰ mol/L. Common examples include acetic acid (Ka = 1.8 × 10⁻⁵) and carbonic acid (Ka = 4.3 × 10⁻⁷).
Q3: What pH range does this formula typically produce?
A: For weak acids, this formula typically produces pH values between 2 and 7, depending on the Ka value and concentration.
Q4: Are there limitations to this formula?
A: This formula assumes the acid is monoprotic and that the concentration of H⁺ from water autoionization is negligible compared to that from the acid dissociation.
Q5: Can this formula be used for strong acids?
A: No, for strong acids that completely dissociate, pH is simply calculated as pH = -log(C), where C is the concentration of the strong acid.