The pH Scale

pH stands for the ‘power of hydrogen’ and represents the concentration of hydrogen ions in a water-based solution

  • pH is expressed on a logarithmic scale, whereby pH = –log10c  (c = concentration of H+ in moles per litre) 

The pH scale typically ranges from 0 – 14 and measures how acidic or basic a substance is

  • Substances with a pH less than 7 are acidic and will donate hydrogen ions (i.e. high H+ concentration)
  • Substances with a pH greater than 7 are basic / alkaline and will accept hydrogen ions (i.e. high OH concentration)
  • Substances with a pH of 7 are neutral (there is an equal number of H+ and OH ions)

The pH Scale

pH scale