pH Calculator

What is pH?

pH is a measure of the acidity or basicity of a solution. It is defined as the negative logarithm (base 10) of the hydrogen ion concentration:

pH = -log₁₀[H⁺]

pH Scale

• Acidic: pH < 7 (higher concentration of H⁺ ions)
• Neutral: pH = 7 (equal concentrations of H⁺ and OH⁻)
• Basic (Alkaline): pH > 7 (higher concentration of OH⁻ ions)

Key Relationships

• pH + pOH = 14 (at 25°C)
• pOH = -log₁₀[OH⁻]
• [H⁺] × [OH⁻] = 1.0 × 10⁻¹⁴ (Kw, at 25°C)
• [H⁺] = 10⁻ᵖᴴ
• [OH⁻] = 10⁻ᵖᴼᴴ

Importance of pH

• Biology: Blood pH must stay between 7.35-7.45 for survival
• Agriculture: Soil pH affects nutrient availability for plants
• Chemistry: pH affects reaction rates and product formation
• Environment: Ocean acidification impacts marine ecosystems
• Industry: pH control is critical in manufacturing and water treatment

Logarithmic Scale

The pH scale is logarithmic, meaning each unit represents a 10-fold difference in hydrogen ion concentration. For example:

• pH 6 is 10 times more acidic than pH 7
• pH 5 is 100 times more acidic than pH 7
• pH 4 is 1,000 times more acidic than pH 7

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