Salt Hydrolysis is the interaction of salt ions with water to produce either acidic or basic solutions. It is effectively the chemical opposite of a neutralization reaction.
The extent of this reaction is called the Degree of Hydrolysis ($h$), and the equilibrium constant is the Hydrolysis Constant ($K_h$).
Weak Acid & Strong Base Salt:
$$\text{pH} = 7 + \frac{1}{2}(pK_a + \log C)$$
Strong Acid & Weak Base Salt:
$$\text{pH} = 7 - \frac{1}{2}(pK_b + \log C)$$
Our calculators use a smartParser to handle scientific notation.
10^5 means 10510*1 means 10 multiplied by 1.1.8e-5 means 1.8 × 10-5Salt hydrolysis is a process in which the constituent ions of a salt react with water to produce either acidity or alkalinity. It is essentially the reverse of a neutralization reaction.
Problem: Calculate the pH of a $0.1\text{ M}$ Sodium Acetate solution ($K_a \text{ of acetic acid} = 1.8 \times 10^{-5}$).
In research labs, the degree of hydrolysis is often determined via Conductometric Titration. As hydrolysis progresses, the change in ion mobility alters the solution's conductivity.
For salts of organic acids/bases, the change in absorption spectra due to hydrolysis allows scientists to calculate the hydrolysis constant ($K_h$) with extreme precision.
Antacid Effect: Baking soda ($NaHCO_3$) works as an antacid because the bicarbonate ion undergoes hydrolysis to produce $OH^-$ ions, neutralizing stomach acid.
Soil pH: Many fertilizers are salts (like Ammonium Sulfate). Their hydrolysis in soil moisture can significantly lower soil pH, affecting crop yield.
Amphiprotic Ions: Salts like $NaH_2PO_4$ can either donate or accept protons depending on the environment, making their hydrolysis calculations uniquely complex.
$Na^+$ and $Cl^-$ are conjugate partners of strong bases/acids. They have negligible affinity for $H^+$ or $OH^-$ ions in water.
It is the equilibrium constant for the hydrolysis reaction. For a WA/SB salt, $K_h = K_w / K_a$.
As concentration ($C$) decreases, the degree of hydrolysis ($h$) increases, though the total shift in pH might become less extreme.
Yes. If $K_a$ of the weak acid exactly equals $K_b$ of the weak base (e.g., Ammonium Acetate), the pH remains 7.0.
When the cation (usually from a weak base) reacts with water to release $H_3O^+$ ions, making the solution acidic.
Generally, yes. Increasing the temperature usually increases the degree of hydrolysis.
For dilute solutions where $h < 0.1$, the relation is $h = \sqrt{K_h / C}$.
Very acidic (pH ≈ 2-3). The $Al^{3+}$ ion has a high charge density, polarizing water molecules to release $H^+$ ions.
Yes. Since $K_h$ depends on $K_w$, any temperature change that shifts $K_w$ will shift the hydrolysis equilibrium.