By Sunil Bhardwaj

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As per Bronsteo-Lowry Concept the strength of an acid is determined by its tendency to give up a proton and the strength of a base is determined by its tendency to accept a proton.

A strong acid has a strong tendency to donate \({ H }^{ + }\) and a strong base has a strong tendency to accept \({ H }^{ + }\).

The position of equilibrium in an acid-base reaction tells us the relative strengths of the acids and bases involved. A Bronsted-Lowry reaction between both strong acid and strong base produce weak acid and weak base. $$ \underset { Strong Acid }{ HA } + \underset { Strong Base }{ { B }^{ - } } \rightleftharpoons \underset { Weak Base }{ { A }^{ - } } + \underset { Weak Acid }{ HB } $$ In the Bronsted-Lowry concept, the classification of acids is done according to their ability to donate protons to a specified base. All strong acids are completely ionized in water forming \({ H }_{ 3 }{ O }^{ + }\) which is the strongest acid that can exist in water. Thus in water, the strengths of all acids (e.g.,\(HCl, HNO_{ 3 }, HCIO_{ 4 }\), etc.) stronger than \({ H }_{ 3 }{ O }^{ + }\) are reduced to the same level of \({ H }_{ 3 }{ O }^{ + }\), i.e., these acids appear to be of equal strength in water which is acting as the base, this effect on the strength of an acid by a solvent is called the leveling effect.

Similarly, all bases stronger (oxide ion\( { O }^{ 2- }\), amide ion \(N{ H }_{ 2 }^{ - }\), hydride ion \({ H }^{ - }\) etc.) reacts completely with water to give \({ OH }^{ - }\) ions. with water as a solvent, the base strengths of these bases are reduced to the same level of \({ OH }^{ - }\) ion. In other words, it is impossible to differentiate their base strengths. Hence the relative strengths of acids stronger than \({ H }_{ 3 }{ O }^{ + }\) cannot be measured in water. One can measure the acid strengths in such cases by using a solvent that does not produce a leveling effect.