pH ماشینحساب
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What Is pH?
pH (potential of hydrogen) measures the acidity or alkalinity of a solution on a scale from 0 to 14. A pH of 7 is neutral (pure water at 25°C). Values below 7 are acidic; above 7 are basic (alkaline).
pH = −log₁₀[H⁺]. Each unit on the pH scale represents a 10-fold change in acidity. Lemon juice (pH 2) is 100,000 times more acidic than water (pH 7).
pH Scale Reference Values
0–2: Strong acids (battery acid, HCl). 3–4: Weak acids (vinegar pH 3, tomatoes pH 4). 5–6: Mild acids (coffee pH 5, milk pH 6.5). 7: Neutral (pure water). 8–9: Mild bases (seawater pH 8, baking soda pH 9). 10–12: Strong bases (milk of magnesia pH 10, bleach pH 12). 13–14: Very strong bases (lye, drain cleaner).
pH in Biology and Chemistry
Human blood maintains a tightly controlled pH of 7.35–7.45. A pH outside 6.8–7.8 is life-threatening. The stomach has a pH of 1.5–3.5 to aid protein digestion.
In chemistry, pH determines reaction rates, enzyme activity, and solubility. Ocean acidification (decreasing ocean pH due to CO₂ absorption) threatens marine ecosystems, particularly coral reefs.
Frequently Asked Questions
What pH is considered neutral?
pH 7 is neutral, corresponding to pure water at 25°C where [H⁺] = [OH⁻] = 10⁻⁷ mol/L. In practice, distilled water may be slightly acidic (pH 5.5–6) due to dissolved CO₂.
What is the pH of common household substances?
Lemon juice: ~2, Vinegar: ~3, Coffee: ~5, Milk: ~6.5, Water: 7, Baking soda: ~9, Bleach: ~12, Drain cleaner: ~14.
How do I convert between pH and H+ concentration?
[H⁺] = 10^(-pH). For pH 3: [H⁺] = 10⁻³ = 0.001 mol/L. For pH 7: [H⁺] = 10⁻⁷ = 0.0000001 mol/L.
آخرین بهروزرسانی: March 2026