How Salts Affect pH
Hydrolysis: The process where ions from salt react with water, affecting the solution's pH.
Cation and Anion Role: Depending on their nature, cations and anions can either increase or decrease the concentration of H⁺ or OH⁻ ions in a solution.
Types of Salts and Their pH
Salts from Strong Acid and Strong Base:
Typically neutral (pH = 7) as they do not affect the H⁺ or OH⁻ concentration significantly.
Example: NaCl, formed from HCl (strong acid) and NaOH (strong base).
Salts from Strong Acid and Weak Base:
Generally acidic (pH < 7) because the cation reacts with water to produce H⁺ ions.
Example: NH₄Cl, formed from HCl (strong acid) and NH₃ (weak base).
Salts from Weak Acid and Strong Base:
Typically basic (pH > 7) since the anion reacts with water to produce OH⁻ ions.
Example: CH₃COONa, formed from CH₃COOH (weak acid) and NaOH (strong base).
Salts from Weak Acid and Weak Base:
The pH depends on the relative strengths of the acid and base.
Example: NH₄CN, formed from HCN (weak acid) and NH₃ (weak base).
Factors Affecting the pH of Salt Solutions
Relative Strength of Parent Acid and Base: Determines whether the solution will be acidic, basic, or neutral.
Concentration of the Solution: Higher concentrations can amplify the acidic or basic nature of the salt.
Temperature: Can affect the degree of hydrolysis and thus the pH.
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