How to calculate hydrogen ion concentation from pH

pH - (log) [H+]

Explanation:

Find the Hydrogen ion concentration;

then the logarithm of that concentration, and change the sign.

If [H+] = 1 x / 10 to the negative 7 (moles per liter), the log of that is - 7, the opposite of that is 7

Ergo, pH 7. IF the acid is very very concentrated, the pH can be negative. This was a very easy one I chose that you likely saw in class, but work on a few more, and it will be easy. When the acids are very very weak disassociation, you will need another, little bit harder equation. Just remember what pH is; "the opposite of the log of hydrogen (or Hydronium ion) concentration.