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 = -logâ‚â‚€[Hâº]
Find H⺠from pH
[Hâº] = 10â»áµ–á´´
Relationship with pOH
pH + pOH = 14
Given Information
[Hâº] = 1.0 × 10â»âµ M
Apply Formula
pH = -logâ‚â‚€(1.0 × 10â»âµ)
Calculate pH
pH = -(-5) = 5.00
Result
pH = 5.00 (Acidic solution)
pOH = 14 - 5 = 9.00
Forgetting the negative sign
pH = -log[Hâº], not log[Hâº]
Using natural logarithm
Use logâ‚â‚€ (base 10), not ln (natural log)
Confusing [Hâº] with pH
Higher pH = lower [Hâº] (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 (Mâ‚Vâ‚ = Mâ‚‚Vâ‚‚)
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⺠and OHâ» ions ([Hâº] = 1.0 × 10â»â· 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[OHâ»]). Knowing one allows you to calculate the other.
The logarithmic scale compresses the wide range of H⺠concentrations (10â° to 10â»Â¹â´ 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