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Hydrogen Ion Concentration – pH Scale

Hydrogen Ion Concentration – pH scale

Sorensen, a Danish biochemist developed a scale to measure the acidity in terms of concentrations of in a solution. As defined by him, “pH of a solution is the negative logarithm to the base 10 of the concentration of H+ ions which it contains.”

or

Just as pH indicates the hydrogen ion concentration, the pOH represents the hydroxyl ion concentration, i.e.,

Considering the relationship,

Taking log on both sides, we have

or

or

 [H+][OH]pHpOH
Acidic solution> 10–7< 10–7< 7> 7
Neutral solution10–7 10–777
Basic solution< 10–7> 10–7> 7< 7

 

pH of some materials

MaterialpHMaterialpH
Gastric juice1.4Rain water6.5
Lemon juice2.1Pure water7.0
Vinegar2.9Human saliva7.0
Soft drinks3.0Blood plasma7.4
Beer4.5Tears7.4
Black coffee5.0Egg7.8
Cow’s milk6.5Household ammonia11.9

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