Calculator Form
Choose an input method, enter your known values, and calculate hydroxide concentration, pOH, and pH in one place.
Example Data Table
These examples assume Kw = 1.0 × 10-14 unless adjusted.
| Scenario | Input | OH Concentration (mol/L) | pOH | pH |
|---|---|---|---|---|
| Given pOH | pOH = 3.00 | 1.000000e-03 | 3.00 | 11.00 |
| Given pH | pH = 9.50 | 3.162278e-05 | 4.50 | 9.50 |
| From H+ | [H+] = 1.0e-09 mol/L | 1.000000e-05 | 5.00 | 9.00 |
| From dilution | C1 = 0.10, V1 = 25, V2 = 250 | 1.000000e-02 | 2.00 | 12.00 |
Formula Used
1) From pOH
[OH⁻] = 10-pOH
2) From pH
pOH = pKw - pH, then [OH⁻] = 10-pOH
3) From hydrogen ion concentration
[OH⁻] = Kw / [H⁺]
4) From moles and volume
[OH⁻] = n / V, where n is moles and V is liters.
5) From dilution
C1V1 = C2V2, so C2 = (C1 × V1) / V2
6) From strong base stoichiometry
[OH⁻] = base molarity × OH released per formula unit
How to Use This Calculator
- Select the calculation mode matching your known input.
- Keep Kw at 1e-14 for common room-temperature problems, or change it when needed.
- Enter your values carefully using scientific notation when useful.
- Press the calculate button to show the result above the form.
- Read OH concentration, pOH, pH, and the method summary.
- Use the graph to see where the point falls on the pH versus OH scale.
- Download your saved history as CSV or the current result as PDF.
Calculation History
Recent calculations are stored during this session.
| Time | Mode | OH (mol/L) | pOH | pH | Kw | Summary |
|---|---|---|---|---|---|---|
| No calculations saved yet. | ||||||
FAQs
1) What does OH concentration mean?
OH concentration means hydroxide ion amount per liter of solution. It helps describe how basic a solution is and connects directly to pOH and pH values.
2) How do I calculate OH concentration from pOH?
Use the relation [OH⁻] = 10-pOH. Enter the pOH value, and the calculator converts it into hydroxide concentration in mol/L instantly.
3) How do I calculate OH concentration from pH?
First find pOH using pOH = pKw - pH. Then calculate hydroxide concentration with [OH⁻] = 10-pOH. This tool performs both steps automatically.
4) Why is pH plus pOH not always 14?
The sum equals pKw, not always 14. At room temperature, pKw is commonly near 14. If temperature changes, Kw changes, so the sum changes too.
5) Can I use this for dilution problems?
Yes. Choose the dilution mode and enter initial concentration, initial volume, and final volume. The calculator applies C1V1 = C2V2 to find the diluted hydroxide concentration.
6) Can strong bases release more than one OH ion?
Yes. Some bases release more than one hydroxide ion per formula unit. Enter that count in the strong base mode to match the correct stoichiometric release.
7) What unit should I use for OH concentration?
Use mol/L for hydroxide concentration. This is the standard concentration unit in acid-base equilibrium work and keeps pOH and pH conversions consistent.
8) Why does the calculator allow changing Kw?
Kw depends on temperature. Allowing manual Kw entry makes the tool more flexible for advanced exercises, lab conditions, and nonstandard equilibrium assumptions.