The hydrogen ion concentration (H+) can be calculated from the pH using the following equation:
[H+] = 10^(-pH)
In this equation, the pH is the negative logarithm (base 10) of the hydrogen ion concentration. By taking the inverse of 10 raised to the power of the negative pH value, you can determine the hydrogen ion concentration.
For example, if you have a pH of 3, the calculation would be:
[H+] = 10^(-3) = 0.001 (or 1 x 10^(-3))
This means that the hydrogen ion concentration in this solution is 0.001 moles per liter (M) or 1 millimole per liter (mM).
It's important to note that pH is a logarithmic scale, so a change of 1 pH unit corresponds to a tenfold change in the hydrogen ion concentration.