P

pH

pH = -log₁₀[H⁺]
Quick Reference
Formula / NotationpH = -log₁₀[H⁺]
Also Known AsHydrogen ion concentration, Acidity, Basicity

What is pH?

A logarithmic scale measuring the acidity or alkalinity of an aqueous solution: pH = -log[H⁺]. A pH of 7 is neutral (at 25°C), below 7 is acidic, and above 7 is basic. The scale typically ranges from 0 to 14. Changes of one pH unit represent a 10-fold change in hydrogen ion concentration.

Formula & Notation

pH = -log₁₀[H⁺]

Other Names / Synonyms: Hydrogen ion concentration, Acidity, Basicity

Properties & Characteristics

The pH scale runs from 0 to 14. Pure water has a pH of 7 (neutral) at 25°C. Each unit change in pH represents a 10-fold change in hydrogen ion concentration. pH < 7 indicates an acidic solution; pH > 7 indicates a basic (alkaline) solution. Temperature affects pH — water at 37°C has a neutral pH of 6.8. The relationship pOH + pH = 14 holds at 25°C.

Uses & Applications

Quality control in food and beverage production. Water treatment and purification. Blood pH monitoring in medicine (normal blood pH: 7.35–7.45). Agriculture: soil pH determines nutrient availability. Swimming pool maintenance. Chemical manufacturing. Pharmaceutical formulation. Environmental monitoring of lakes, rivers, and rain (acid rain has pH < 5.6).

Safety Information

Extremely acidic solutions (pH 0–2) and extremely basic solutions (pH 12–14) are corrosive and can cause severe burns. Always wear gloves and eye protection when working with pH-altering chemicals. Neutralize acid spills with sodium bicarbonate. Buffer solutions should be stored carefully.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term pH
Formula pH = -log₁₀[H⁺]
Synonyms Hydrogen ion concentration, Acidity, Basicity

Frequently Asked Questions

A logarithmic scale measuring the acidity or alkalinity of an aqueous solution: pH = -log[H⁺]. A pH of 7 is neutral (at 25°C), below 7 is acidic, and above 7 is basic. The scale typically ranges from 0 to 14. Changes of one pH unit represent a 10-fold change in hydrogen ion concentration.

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