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Ch.17 - Aqueous Ionic Equilibrium
Chapter 17, Problem 55c

Blood is buffered by carbonic acid and the bicarbonate ion. Normal blood plasma is 0.024 M in HCO3- and 0.0012 M H2CO3 (pKa1 for H2CO3 at body temperature is 6.1).
c. Given the volume from part (b), what mass of NaOH can be neutralized before the pH rises above 7.8?

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Buffer Systems

Buffer systems are solutions that resist changes in pH upon the addition of small amounts of acids or bases. In blood, the carbonic acid (H2CO3) and bicarbonate ion (HCO3-) work together to maintain a stable pH, crucial for physiological functions. The equilibrium between these two components allows the blood to neutralize excess acids or bases, keeping the pH within a narrow range.
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pKa and Acid-Base Equilibrium

The pKa value is a measure of the strength of an acid in solution, indicating the pH at which half of the acid is dissociated. For carbonic acid, with a pKa of 6.1, this means that at pH 6.1, the concentrations of H2CO3 and HCO3- are equal. Understanding pKa is essential for predicting how the buffer system will respond to added acids or bases, such as NaOH in this case.
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Neutralization Reactions

Neutralization reactions occur when an acid reacts with a base to form water and a salt, effectively reducing the acidity or basicity of the solution. In this scenario, adding NaOH (a strong base) to the buffered solution will react with H2CO3, leading to the formation of HCO3- and water. Calculating the mass of NaOH that can be added before the pH exceeds 7.8 involves understanding the stoichiometry of the reaction and the buffer capacity.
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