Biochemistry unit-1: The pH Scale

 Hello friends, in today's, article we see what is the pH Scale and its importance in biological reaction. let's begin.

The pH Scale:

• In 1909, Soren Sorensen, a danish biochemist used a logarithmic scale for expressing the H⁺ concentration this scale called the pH Scale.
• He defined the pH of a solution as the negative logarithm of the concentration of hydrogen ion, thus   pH = Log 1/[H⁺] = -Log[H⁺]    where the symbol p denotes "negative logarithm".
• The ion product of water, Ka is the basis for the pH Scale. (see image)
  
  
  
• It is a convenient means of designing the actual concentration of H⁺ in an aqueous solution in the range between 1.0M,  H⁺ cand 1.0M OH^-.

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• Biochemical reactions are often defined in terms of hydrogen ion concentration.
• For precisely neutral solution at 25 celsius, in which the concentration of hydrogen ions is   1.0*10^-7, the pH can be calculated as follows                                                                                                     pH= Log 1/1*10^-7                                                                                                                                pH= Log(1*10⁷)                                                                                                                                 pH= Log 1.0+ Log10⁷                                                                                                                         pH= 0 + 7.0                                                                                                                                         pH  = 7.0
• To calculate the pH of a Solution   

1. Calculate hydrogen ion Concentration
2. Calculate the base 10 logarithms of [H⁺]
3. pH is the negative of the value found in step 2

for example, for pure water at 25 celsius:

 pH = -Log[H⁺] = -Log 10^-7 = -(-7)  = 7

• The acidity of the solution: the number of hydrogen ions present in a solution, is known as the acidity of the solution.
• The alkalinity of a solution: alkalinity is dependent upon the number of hydroxyl ions present, is called the alkalinity of a solution.
• The pH scale was developed by taking water as the standard solution.
• It is an experimental fact that only 1 mole in 5,50,000,000 moles of water ionizes into a [H⁺] and OH^-. This is the same proportion as 1 gram hydrogen ion in 10,000,000 litre of water. Hence, 1 litre of water contains 1/10,000,000 of a gram of H⁺.
• Later for every day use the 'power' figure was used and the symbol pH placed before it.

so this is all about the pH scale.

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