A buffer contains 0.10 mol of acetic acid and 0.13 mol of sodium acetate in 1.00 L. b. What is the pH of the buffer after the addition of 0.020 mol of KOH?
Ch.17 - Additional Aspects of Aqueous Equilibria
Chapter 17, Problem 29a
(a) What is the ratio of HCO3- to H2CO3 in blood of pH 7.4?

1
Identify the relevant chemical species involved, which are bicarbonate ion (HCO3-) and carbonic acid (H2CO3).
Recognize that the relationship between these species in solution can be described by the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where A- is the conjugate base (HCO3-) and HA is the acid (H2CO3).
Find the pKa value for the dissociation of H2CO3 into HCO3-. This value is typically around 6.1 for carbonic acid.
Substitute the known values into the Henderson-Hasselbalch equation: 7.4 = 6.1 + log([HCO3-]/[H2CO3]).
Solve the equation for the ratio [HCO3-]/[H2CO3] by isolating the ratio on one side of the equation.

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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 in biological fluids, such as blood, help maintain pH stability. The bicarbonate (HCO3-) and carbonic acid (H2CO3) system is a crucial buffer that resists changes in pH by neutralizing excess acids or bases. This balance is vital for physiological processes, as even slight deviations in pH can affect enzyme activity and metabolic functions.
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Buffer Capacity
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation relates the pH of a solution to the concentration ratio of an acid and its conjugate base. For the bicarbonate buffer system, it is expressed as pH = pKa + log([HCO3-]/[H2CO3]). This equation allows for the calculation of the ratio of bicarbonate to carbonic acid at a given pH, which is essential for understanding acid-base balance in the blood.
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Henderson-Hasselbalch Equation
Physiological pH and Homeostasis
Physiological pH refers to the normal pH range of human blood, which is approximately 7.35 to 7.45. Maintaining this pH is crucial for homeostasis, as it ensures optimal conditions for biochemical reactions. Deviations from this range can lead to acidosis or alkalosis, conditions that can disrupt cellular functions and overall health.
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The pH Scale
Related Practice
Textbook Question
Textbook Question
A buffer contains 0.10 mol of acetic acid and 0.13 mol of sodium acetate in 1.00 L. c. What is the pH of the buffer after the addition of 0.020 mol of HNO3?
Open Question
A buffer contains 0.15 mol of propionic acid (C2H5COOH) and 0.10 mol of sodium propionate (C2H5COONa) in 1.20 L. (a) What is the pH of this buffer? (b) What is the pH of the buffer after the addition of 0.01 mol of NaOH? (c) What is the pH of the buffer after the addition of 0.01 mol of HI?
Textbook Question
(b) What is the ratio of HCO3- to H2CO3 in an exhausted marathon runner whose blood pH is 7.1?
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Textbook Question
You have to prepare a pH = 3.50 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4. Which solutions would you use?
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Textbook Question
You have to prepare a pH = 3.50 buffer, and you have the following 0.10 M solutions available: HCOOH, CH3COOH, H3PO4, HCOONa, CH3COONa, and NaH2PO4. How many milliliters of each solution would you use to make approximately 1 L of the buffer?