Hydrogen Ion Concentration Calculator
Calculate the hydrogen ion concentration [H⁺] from pH or pOH. Determine acidity from ion concentrations.
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What is hydrogen ion concentration?
[H⁺] (or [H₃O⁺]) is the concentration of hydrogen ions in solution, measured in mol/L (M). Pure water at 25°C has [H⁺] = 1×10⁻⁷ M. pH = -log[H⁺], so [H⁺] = 10^(-pH). Acidic solutions have higher [H⁺].
How do you calculate [H⁺] from pH?
[H⁺] = 10^(-pH). At pH 7: [H⁺] = 10⁻⁷ M. At pH 2: [H⁺] = 10⁻² = 0.01 M. 5 pH units = 100,000× more H⁺. Strong acids (pH < 2) have [H⁺] approaching their concentration.
What is the relationship between pH and pOH?
pH + pOH = 14 at 25°C. If pH = 7 (neutral): pOH = 7. If pH = 2 (acidic): pOH = 12. In basic solutions: pOH < 7, pH > 7. This relationship comes from the water ionization constant: Kw = [H⁺][OH⁻] = 10⁻¹⁴.
What is the pH scale?
pH ranges from 0 to 14: pH < 7 = acidic, pH = 7 = neutral, pH > 7 = basic. Each unit represents 10× change in [H⁺]. Stomach acid: pH 1-2 (very acidic). Lemon juice: pH 2 (acidic). Water: pH 7 (neutral). Baking soda: pH 8-9 (basic). Drain cleaner: pH 13-14 (very basic).