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pH of Salt Solution Formula:
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The hydrolysis approximation formula calculates the pH of a salt solution formed from a weak acid and strong base. The equation is derived from the relationship between water's autoionization constant and the acid dissociation constant.
The calculator uses the hydrolysis approximation formula:
Where:
Explanation: This approximation applies specifically to salts of weak acids where the conjugate base hydrolyzes water, producing a basic solution.
Details: Understanding the pH of salt solutions is crucial in analytical chemistry, buffer preparation, and predicting the behavior of compounds in aqueous environments. Many biological and chemical processes are pH-dependent.
Tips: Enter pKw (typically 14.00 at 25°C) and the pKa value for the weak acid. The calculator will compute the expected pH of the salt solution using the hydrolysis approximation.
Q1: When is this approximation valid?
A: This approximation works best for salts of weak acids with strong bases where the concentration is not extremely dilute.
Q2: What is the typical value of pKw?
A: pKw is approximately 14.00 at 25°C, but it varies with temperature (e.g., 13.99 at 0°C, 13.62 at 50°C).
Q3: How accurate is this approximation?
A: It provides a reasonable estimate but becomes less accurate for very dilute solutions or when the acid is not particularly weak.
Q4: Does this work for salts of weak bases?
A: No, this specific formula is for salts of weak acids. Different formulas apply to salts of weak bases.
Q5: What if my salt comes from a diprotic acid?
A: For diprotic acids, the calculation is more complex and depends on which proton is being considered.