Calculate pH from hydrogen ion concentration and visualize acidity or basicity on the pH scale
Unit: mol/L (M)
Use scientific notation for very small values (e.g., 1e-5 for 0.00001)
The pH calculator determines the acidity or basicity of a solution by calculating the negative logarithm of hydrogen ion concentration. It provides pH value, corresponding pOH value, and visual representation on the pH scale from 0 (strongly acidic) to 14 (strongly basic).
pH = -log₁₀[H⁺]
Find H⁺ from pH
[H⁺] = 10⁻ᵖᴴ
Relationship with pOH
pH + pOH = 14
Given Information
[H⁺] = 1.0 × 10⁻⁵ M
Apply Formula
pH = -log₁₀(1.0 × 10⁻⁵)
Calculate pH
pH = -(-5) = 5.00
Result
pH = 5.00 (Acidic solution)
pOH = 14 - 5 = 9.00
Forgetting the negative sign
pH = -log[H⁺], not log[H⁺]
Using natural logarithm
Use log₁₀ (base 10), not ln (natural log)
Confusing [H⁺] with pH
Higher pH = lower [H⁺] (inverse relationship)
Wrong concentration units
Must use mol/L (M), not g/L or mmol/L
Calculate buffer solution pH and capacity
Calculate acid dissociation constant
Calculate solution dilution (M₁V₁ = M₂V₂)
pH is a measure of acidity or basicity on a scale from 0-14. It's crucial in chemistry, biology, and environmental science because it affects chemical reactions, enzyme activity, and organism survival.
pH 7 is neutral, meaning equal concentrations of H⁺ and OH⁻ ions ([H⁺] = 1.0 × 10⁻⁷ M). Pure water at 25°C has pH 7. pH < 7 is acidic, pH > 7 is basic.
pH is measured using pH meters (electronic), pH paper (color-change strips), or pH indicators (chemicals that change color at specific pH ranges). pH meters are most accurate.
Yes, for extremely concentrated acids or bases. For example, 10 M HCl has pH ≈ -1. However, the 0-14 scale covers most common aqueous solutions.
pH + pOH = 14 at 25°C. pOH measures hydroxide ion concentration (pOH = -log[OH⁻]). Knowing one allows you to calculate the other.
The logarithmic scale compresses the wide range of H⁺ concentrations (10⁰ to 10⁻¹⁴ M) into a manageable 0-14 scale. Each pH unit represents a 10-fold difference in acidity.
Temperature affects pH because water's autoionization constant (Kw) changes with temperature. At higher temperatures, neutral pH is slightly below 7; at lower temperatures, slightly above 7.
Stomach acid: pH 1-2, Lemon juice: pH 2, Vinegar: pH 3, Coffee: pH 5, Pure water: pH 7, Blood: pH 7.4, Baking soda: pH 9, Ammonia: pH 11, Bleach: pH 13.
Education
Acid-base chemistry courses and lab experiments
Laboratory
Quality control and solution preparation
Industry
Water treatment, food processing, pharmaceuticals
Environmental
Monitoring soil, water bodies, and ecosystems