The main buffering agents in human blood are h2co3 and hco3. Explain how this buffering system will be able to maintain blood pH at a steady level when a small amount of a generic acid HA ( with ions H+ and A-) is added

The base, HCO₃⁻ of the buffering system will neutralize the acid added forming H₂CO₃.

Explanation:

A buffer solution keeps the pH in a narrow range upon the addition of an acid or base. A buffer consists of a pair of a weak acid and its conjugate base, or vice versa, in a pair of a weak base and its conjugate acid. In the case of human blood, the acid is H₂CO₃ and its conjugate base is HCO₃⁻.

The buffering system of the human blood maintain blood pH at a steady level when a small amount of a generic acid HA is added in the following way:

HCO₃⁻ + HA  ⇄  H₂CO₃ + A⁻

The base, HCO₃⁻, will neutralize the acid added forming the H₂CO₃, which is already a component of the buffering system of the human blood. Thus, hydronium ions of the acid added are removed, preventing the pH of blood from becoming acidic.                

On the other hand, when a small amount of a generic base A⁻ is added the following reaction takes place:    

H₂CO₃ + A⁻  ⇄  HCO₃⁻ + HA

In this case, the acid H₂CO₃ will neutralize the base added to form the base HCO₃⁻, which is already a component of the buffering system. Thus, the base added are removed from the blood, preventing the pH of blood from becoming basic.  

Since, the acid or its conjugate base will react with the base or acid added, to neutralizing it and forming the species that conform the buffer solution, the pH is being maintained at a steady level.  

In the process above, the addition of a small amount of an acid or a base won't change in a significant way the concentrations of the two components of the buffering system. This buffering mechanism prevents the blood from becoming acidic or basic.  

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