Chemistry
Calculator for pH
Calculate pH from hydrogen ion concentration; see pOH, hydroxide concentration and whether the result na acid or base too.
Add to workspaceYour numbers
Enter concentration wey pass zero in moles per litre — 0.0001 mean 10−4 mol/L. Results dey update as you dey type. All calculations dey run inside your browser on your device.
pH
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Formula
pH = −log10[H⁺]. At 25 °C, pH + pOH = 14, and [H⁺] × [OH⁻] = 10−14, so pOH = 14 − pH and [OH⁻] = 10−14 ÷ [H⁺]. Below 7 na acidic, 7 na neutral, and above 7 na alkaline.
Example wey show the calculation
[H⁺] = 0.0001 mol/L = 10−4 mol/L: pH = −log10(10−4) = 4.00. pOH = 14 − 4.00 = 10.00, and [OH⁻] = 10−14 ÷ 10−4 = 10−10 mol/L. The solution acidic; the acidity fit resemble tomato juice.
Where e fit work and limits
Dis model use di free hydrogen ion concentration wey you enter for mol/L as approximation to activity. E assume aqueous solution at 25 °C and use pH + pOH ≈ 14. Results based on concentration na approximations even for dilute solutions; concentrated solutions fit differ well-well. Acid strength no be di same as concentration. E no calculate weak-acid dissociation. Dis na calculation aid, no be guidance for handling chemicals.
Questions wey people dey ask often
Why the scale dey logarithmic?
Because concentrations fit differ by many powers of ten: stomach acid at pH 2 get 10,000 times the hydrogen ions wey pH 6 solution get, no be three times. Every full pH step mean tenfold change.
pH 7 always mean neutral?
Na only at 25 °C. Neutral mean [H⁺] = [OH⁻], and temperature dey shift that balance point, so neutral water at 100 °C get pH 6.14.
pH fit be negative or pass 14?
Yes, for acids or bases wey concentrate well well — 10 mol/L strong acid get nominal pH of −1. The 0–14 range na rough guide for dilute solutions, no be law.
How pH differ from pOH?
pH describe hydrogen ion activity; pOH describe hydroxide ion activity. Dis model wey use concentration approximate their sum as 14 at 25 °C. Di relation change with temperature.
Why the pH wey I measure differ from the calculated one?
Meters dey measure activity, no be concentration; temperature, calibration and dissolved salts fit all shift readings. For weak acids, incomplete dissociation usually dey cause bigger difference — the concentration wey you enter no be the free [H⁺].
Which familiar thing I fit use compare am?
Pure water get pH 7; coffee about 5; vinegar about 2.4; baking soda solution about 8.3; household bleach about 12.5.
Original reference sources
Other tools wey relate to dis
- Converter for temperature — the neutral point of pH dey depend on temperature
- Tool to convert length units — litres, millilitres and other lab units
- Converter for volume units — solution volumes for dilution work
Results na estimates; dem no replace advice from qualified professional.