Chemistry
pH from hydrogen ion concentration
The definition. Take the base ten logarithm of the concentration in moles per litre and change its sign, which turns small negative logarithms into the familiar positive pH scale.
The Formula
pH = -log10[H+]
The definition. Take the base ten logarithm of the concentration in moles per litre and change its sign, which turns small negative logarithms into the familiar positive pH scale.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| H | Hydrogen ion concentration | moles per litre | In moles per litre; 0.001 gives a pH of 3. |
| pH | pH value | dimensionless | Lower means more acidic; 7 is neutral at 25 degrees. |
What Each Symbol Means
Hmoles per litre
Hydrogen ion concentration
In moles per litre; 0.001 gives a pH of 3.
pHdimensionless
pH value
Lower means more acidic; 7 is neutral at 25 degrees.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate ph page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate pH, filed under Science. Every number the guide produces comes from substituting into this one line.