Q. How to calculate Hydrogen Ion Concentration?

Ans.

The hydrogen ion concentration has a significant role to play in growth of bacteria as every microorganism has a minimal, maximal and an optimum pH at which it can exist and thrive. The pH, as you may already know, is defined as the negative logarithm of the reciprocal of the hydrogen ion concentration, expressed as:

pH = - log 1/(H⁺)

The pure water when ionized contains lo-' moles each of H+ and OH-. As there is a balance between H+ and OH- ions, the solution (water) is neutral (pH 7). A pH scale has been devised to indicate the pH of various foods. The pH of water being neutral (pH 7), it is the mid point of the scale. The pH scale extends from 0-14. Any substance is known to be alkaline if the pH is above 7. Most of the bacteria prefer a pH near 7 (neutrality), whereas, there are some bacteria which prefer alkaline or acidic medium. In general, yeasts and moulds are more acid tolerant than bacteria.