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Bronsted Theory of Acids & Bases

Bronsted Theory of Acids & Bases

pH Scale With Labels
Introduction: The human body has a pH level of 7.36. The smallest change in this pH level can dramatically affect metabolism in our bodies. An understanding of how the concentration of hydrogen ions can be changed in medicine, such as with metabolic acidosis, requires that we have a deeper understanding of the Bronsted-Lowry theory of acids and bases. This theory defines acids and bases in terms of whether they accept or donate protons (hydrogen ions).

Generally, Bronsted-Lowry acids are substances that donate [math]"H"^"+"[/math], or hydrogen ions, in aqueous solution. On the other hand, Bronsted-Lowry bases are substances that donate [math]"H"^"+"[/math] ions in aqueous solution. For every Bronsted-Lowry acid, there is a conjugate base, which is the species that results from removing a hydrogen ion from the Bronsted-Lowry acid. For every Bronsted-Lowry base, there is a conjugate acid, which is the species that results from adding a hydrogen ion to the Bronsted-Lowry base.

One example of how Bronsted-Lowry acids work is shown below:
[math]H_2SO_4 (aq) + H_2O (l) rarr HSO_4^"-" (aq) + H_3O^"+" (aq) [/math]

In this example, [math]H_2SO_4[/math] represents the Bronsted-Lowry acid, since it donates a proton to water to form its conjugate base, [math]HSO_4^"-"[/math]. On the other hand, water represents the Bronsted-Lowry base, since it accepts a proton from [math]H_2SO_4[/math] to form its conjugate base, [math]H_3O^"+"[/math].

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