pH Calculations

• • pH is a measure of the hydrogen ion concentration in a solution.

  pH = -log [H+]

  • The pH scale normally goes from 0 (very acidic) to 14 (very alkaline).
  • pH 7 is regarded as being neutral.
  • Solutions that have a very low pH include strong acids such as HCl and H2SO4.
  • Strong bases such as NaOH and KOH have a very high pH.
  • Pure water has a pH of 7 and is neutral.

  Calculating [H+] from the pH:

  [H+]= 10^-pH
• • In monobasic acids, each mole of acid produces one mole of hydrogen ions. This means the H+ concentration is the same as the acid
  • So, if you know the concentration of the acid you know the H+ concentration and you can calculate the pH.
  • In diprotic acids you will need to double the [H+] concentration.