What is pH

A pH is the measure of acidity and basicity of a solution. Before understanding the terms acidity and basicity we must know what is an acid or a base? An acid is a molecule which dissociates in water to give hydrate ions and a base would dissociate to give hydroxyl ions. However according to Bronsted-Lowery definition an acid donated hydrogen ion and a base donates hydroxyl ion. pH is thus the measurement of how much acid or how much of basic content does a solution have. This unit of measurement has a neutral point at 7. Water is said to be neutral as its pH is 7 i.e. it is neither acidic nor basic in nature. Solutions with pH less than 7 are called acidic while that pH greater than 7 is called basic in nature. A low pH indicates a high concentration of hydronium ion and thus the solution is called acidic. Now we might wonder that how can a greater concentration of hydronium ion make the solution acidic? This is so because as the acid donated a hydrate ion, the hydrogen ion being a very unstable molecule combines with the water molecule present in the solution to form hydronium ion. Thus more the hydronium ion, more the acidic the solution is. Conversely, a low hydronium ion concentration indicated that the solution is basic and the pH is high.

pH is defined as “negative logarithm to the base 10 of the total number of molecules of the H plus ions present in the solution or the molar concentration of the hydronium ions in the solution”. There is no upper or lower limit of a pH value, it could be both lesser than 0 or could be more than 14. The term pH and its meaning were given by a Danish chemist, but however the meaning of “p” in the term is yet unknown. Some consider it as “power” others as “potential”. A pH meter was developed by Arnold Beckman to measure the pH of any solution and it would change its colour accordingly. For instance, the litmus paper becomes red in contact with acid and blue with contact with a base. All the intercellular and cellular processes are confined within the pH scale of 6 to 8 i.e. they are neither to acidic nor to basic in nature.

Conclusion : 

A pH is a way of measuring the two most important terms related to life and chemistry, which has made drug and medicinal use of chemicals and compounds so easy. It is a useful way to find out the proton or the hydrogen ion concentration of a solution in a mixed state.