pH of a Solution
Measures how acidic or basic a solution is.
\text{pH} = -\log[H^+]
1What it means
pH is the negative logarithm of the hydrogen-ion concentration. pH 7 is basic.
2Variables
| Symbol | Meaning |
|---|---|
| [H^+] | Hydrogen-ion concentration (mol/L) |
3Worked examples
Example 1 Worked solution
Q. Find the pH of a solution with [H⁺] = 0.001 mol/L.
- pH = −log[H⁺] = −log(0.001).
- 0.001 = 10⁻³, so −log(10⁻³) = 3.
✓ pH = 3 (acidic)
4Where it's used
- ✦Testing acidity of water, soil and blood.
- ✦Controlling reactions that depend on acidity.
5Tips & common mistakes
- !A drop of 1 pH unit means 10× more acidic.
- !pH + pOH = 14 at room temperature.