Example 1: pH from [H+] = 2.5×10−4 M
- Formula: pH = −log10[H+].
- Compute: pH = −log10(2.5×10−4) = −(log 2.5 − 4) ≈ −(0.398 − 4) = 3.60.
- At 25°C, pOH = 14 − pH = 10.40; solution is acidic.
pH & pOH Calculator
For acid-base chemistry calculations.
Enter any one value to calculate the others. Use 'e' for scientific notation (e.g., 1.5e-5).
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25°C (Standard)
100°C
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Acidic 7
Neutral 14
Basic
Acidic 7
Neutral 14
Basic
💡 Quick converters for common calculations. Supports: 1e-7, 1×10⁻⁷, 1*10^-7
Calculate pH from [H⁺] Formula: pH = -log₁₀[H⁺]
Calculate pOH from [OH⁻] Formula: pOH = -log₁₀[OH⁻]
💡 Common Concentrations:
- • Pure water (25°C): [H⁺] = 1.0×10⁻⁷ M → pH = 7.00
- • Stomach acid: [H⁺] ≈ 0.01-0.1 M → pH ≈ 1-2
- • Blood: pH ≈ 7.35-7.45
- • Household ammonia: pH ≈ 11-12
Calculate buffer pH using the Henderson-Hasselbalch equation
💡 Henderson-Hasselbalch Equation:
pH = pKa + log₁₀([A⁻]/[HA])
- • When [A⁻] = [HA], pH = pKa (optimal buffering)
- • Effective buffer range: pKa ± 1
- • Buffer capacity depends on total concentration
Convert between acid and base dissociation constants
Acid Constants
Base Constants
| Compound | Ka | pKa | Action |
|---|
💡 Key Relationships:
- • Ka × Kb = Kw (at 25°C: 1.0×10⁻¹⁴)
- • pKa + pKb = pKw (at 25°C: 14)
- • pKa = -log₁₀(Ka)
- • Smaller pKa → Stronger acid
- • Smaller pKb → Stronger base
Generate and visualize acid-base titration curves
Analyte (in flask)
Titrant (in burette)
📊 Titration Analysis:
Calculate pH and species distribution for polyprotic acids
Species Distribution vs pH
💡 About Polyprotic Acids:
- • Have multiple ionizable protons (H⁺)
- • Each deprotonation has its own Ka and pKa
- • Ka₁ > Ka₂ > Ka₃ (successive ionization)
- • Used in buffer systems (e.g., phosphate buffer)
- • Important in biological systems
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