Calculator Input
Formula Used
Weak acid salt: Kh = Kw / Ka. The calculator solves x² / (C - x) = Kh for hydroxide concentration.
Weak base salt: Kh = Kw / Kb. The calculator solves x² / (C - x) = Kh for hydrogen ion concentration.
Weak acid and weak base salt: pH = 1/2(pKw + pKa - pKb). Hydrolysis fraction is estimated with sqrt(Kh) / (1 + sqrt(Kh)).
Neutral salt: pH = pKw / 2 under ideal dilute conditions.
Example Data Table
| Salt | Type | C | Ka | Kb | Expected Result |
|---|---|---|---|---|---|
| Sodium acetate | Weak acid salt | 0.100 M | 1.8e-5 | Not needed | Basic solution near pH 8.87 |
| Ammonium chloride | Weak base salt | 0.100 M | Not needed | 1.8e-5 | Acidic solution near pH 5.13 |
| Ammonium acetate | Weak acid and weak base salt | 0.100 M | 1.8e-5 | 1.8e-5 | Nearly neutral solution |
| Sodium chloride | Strong acid and strong base salt | 0.100 M | Not needed | Not needed | Neutral under ideal conditions |
How to Use This Calculator
- Enter the salt or sample name.
- Select the correct hydrolysis type.
- Enter molar concentration after dilution.
- Enter Ka, Kb, or both, based on salt type.
- Keep Kw at 1.0e-14 for common room temperature work.
- Change Kw when using another temperature reference.
- Press the calculate button.
- Review pH, ion levels, hydrolysis percent, and exports.
Hydrolysis Reaction Overview
Hydrolysis happens when water reacts with ions or molecules. In salt solutions, it often changes pH. A salt may come from a weak acid, a weak base, or both. Those origins decide whether the solution becomes acidic, basic, or nearly neutral.
Why Hydrolysis Matters
Chemists use hydrolysis calculations during titration work, buffer checks, and classroom experiments. The idea is simple. An ion takes a proton from water, or gives a proton to water. That shift creates hydrogen ions or hydroxide ions. The calculator estimates that shift from concentration and equilibrium constants.
Weak Acid Salt Behavior
A salt made from a weak acid and strong base contains a basic anion. The anion reacts with water. It forms the weak acid and hydroxide. The hydrolysis constant equals water ion product divided by acid dissociation constant. A smaller acid constant usually means stronger anion hydrolysis. That often raises pH.
Weak Base Salt Behavior
A salt made from a weak base and strong acid contains an acidic cation. The cation gives a proton effect to water. It forms hydrogen ions in solution. The hydrolysis constant equals water ion product divided by base dissociation constant. A weaker base gives stronger cation hydrolysis. That often lowers pH.
Weak Acid and Weak Base Salts
Some salts contain both hydrolyzing ions. Their pH depends on both acid and base constants. If the acid side dominates, pH falls. If the base side dominates, pH rises. The calculator also estimates hydrolysis percent for this case.
Good Input Practice
Use molar concentration after dilution. Enter reliable constants at the same temperature. Water ion product changes with temperature. The default value suits common room temperature work. For warmer or colder systems, change it. Do not use the result as a safety decision alone. Use lab controls and verified methods.
Reading the Result
Review pH first. Then check the hydrolysis percent. A very small percent means limited reaction. A large percent means water reaction is important. The ion concentration helps compare samples. Export the result when you need reports, worksheets, or repeated lab records.
Limitations
This tool uses equilibrium approximations. It cannot replace activity corrections, full speciation software, or teacher review for concentrated, mixed, or complex samples in advanced work.
FAQs
What is hydrolysis in salt chemistry?
Hydrolysis is a reaction between water and dissolved ions. It can create hydrogen ions or hydroxide ions, which changes pH.
Which salts give basic hydrolysis?
Salts from weak acids and strong bases usually give basic hydrolysis. Their anions react with water and produce hydroxide ions.
Which salts give acidic hydrolysis?
Salts from weak bases and strong acids usually give acidic hydrolysis. Their cations increase hydrogen ion concentration in water.
What does Kh mean?
Kh is the hydrolysis constant. It relates hydrolysis strength to Kw and the acid or base dissociation constant.
Why is Kw included?
Kw represents water ionization. It changes with temperature, so it helps calculate pH more correctly for different conditions.
Can I use this for concentrated solutions?
Use caution. Concentrated solutions may need activity corrections. This calculator is best for ideal or reasonably dilute classroom cases.
What is hydrolysis percent?
Hydrolysis percent estimates the portion of salt ions reacting with water. Higher values mean hydrolysis has stronger influence.
Why do weak acid and weak base salts need both constants?
Both ions can hydrolyze. Ka and Kb show which side dominates, so both constants are needed for pH estimation.