MihsabaHow to use
pH is based on hydrogen-ion concentration and pOH on hydroxide-ion concentration. Near 25°C in dilute aqueous solutions, pH+pOH≈14.
- Choose H⁺ or OH⁻ input.
- Enter concentration in mol/L.
- Apply the logarithm.
- Review pH, pOH and complementary ion concentration.
How it is calculated
pH=−log₁₀[H⁺]; pOH=−log₁₀[OH⁻]; pH+pOH=14
Example
If [H⁺]=10⁻³ mol/L, pH=3 and pOH≈11 under the 25°C approximation.
Important notes
Concentrated/non-ideal solutions require activities rather than simple concentrations, and Kw changes with temperature.
Frequently asked questions
Is pH always 0–14?
Not necessarily for concentrated solutions; that range is common for dilute aqueous systems.
Why logarithms?
H⁺ concentrations span many orders of magnitude.
Is pH+pOH always 14?
No, 14 corresponds approximately to Kw near 25°C.