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Questions and Answers
What is the pKa value of Cacodylic acid?
What is the pKa value of Cacodylic acid?
- 6.2 (correct)
- 6.5
- 7.0
- 6.0
What is the major role of the phosphate buffer system?
What is the major role of the phosphate buffer system?
- Regulating body temperature
- Promoting enzymatic reactions
- Facilitating respiration
- Stabilizing blood pH (correct)
Which acid has a conjugate base with a pKa of 3.75?
Which acid has a conjugate base with a pKa of 3.75?
- Lactic acid
- Propanoic acid
- Formic acid (correct)
- Acetic acid
In the phosphate buffer system, what is the ratio of HPO4^2- to H2PO4^- at pH 7.4?
In the phosphate buffer system, what is the ratio of HPO4^2- to H2PO4^- at pH 7.4?
Which of the following is NOT a physiological buffer system mentioned?
Which of the following is NOT a physiological buffer system mentioned?
What is the pKa for the imidazole buffer?
What is the pKa for the imidazole buffer?
What is the correct expression for the equilibrium constant (Keq) in terms of acid dissociation constant (Ka)?
What is the correct expression for the equilibrium constant (Keq) in terms of acid dissociation constant (Ka)?
Which weak acid has a conjugate base that is involved in buffering at pKa 12.4?
Which weak acid has a conjugate base that is involved in buffering at pKa 12.4?
What is the effect of bicarbonate in the carbonic acid/bicarbonate system?
What is the effect of bicarbonate in the carbonic acid/bicarbonate system?
How would you describe a buffer system in terms of its components?
How would you describe a buffer system in terms of its components?
Which weak acid has a pKa value closest to 4.76?
Which weak acid has a pKa value closest to 4.76?
What is the pH of a solution if the concentration of the proton donor is 0.01 M and the concentration of the conjugated base is also 0.01 M with pKa being 4.76?
What is the pH of a solution if the concentration of the proton donor is 0.01 M and the concentration of the conjugated base is also 0.01 M with pKa being 4.76?
What is the primary component of the phosphate buffer system?
What is the primary component of the phosphate buffer system?
In calculating the pH of weak acid solutions, if the Ka for acetic acid (CH3COOH) is 1.74 x 10^-5, which aspect is crucial for determining the concentration of H+?
In calculating the pH of weak acid solutions, if the Ka for acetic acid (CH3COOH) is 1.74 x 10^-5, which aspect is crucial for determining the concentration of H+?
What is the primary function of buffers in biological systems?
What is the primary function of buffers in biological systems?
Which of the following solutions would you expect to have a higher pH than the physiological pH of blood (7.4)?
Which of the following solutions would you expect to have a higher pH than the physiological pH of blood (7.4)?
When utilizing the Henderson-Hasselbalch equation, what is the relationship between pH, pKa, and the ratios of acid and base forms?
When utilizing the Henderson-Hasselbalch equation, what is the relationship between pH, pKa, and the ratios of acid and base forms?
Which of the following statements accurately describes the effect of pH on biochemical processes?
Which of the following statements accurately describes the effect of pH on biochemical processes?
If the dissociation constant (Ka) of a weak acid is increased, what would be the expected impact on the pH of its solution?
If the dissociation constant (Ka) of a weak acid is increased, what would be the expected impact on the pH of its solution?
When applying the Henderson-Hasselbalch equation, what does a lower pKa indicate about the acid?
When applying the Henderson-Hasselbalch equation, what does a lower pKa indicate about the acid?
What does a high concentration of hydronium ions ($H_3O^+$) indicate about a solution?
What does a high concentration of hydronium ions ($H_3O^+$) indicate about a solution?
Which of the following represents the correct relationship between pH and pOH in a solution?
Which of the following represents the correct relationship between pH and pOH in a solution?
What term is used for a pair of compounds where one acts as a proton donor and the other as a proton acceptor?
What term is used for a pair of compounds where one acts as a proton donor and the other as a proton acceptor?
In the dissociation of acetic acid ($CH_3COOH$), what is the conjugate base formed?
In the dissociation of acetic acid ($CH_3COOH$), what is the conjugate base formed?
Which of the following describes a characteristic of weak acids?
Which of the following describes a characteristic of weak acids?
What is the ion product of water ($K_w$) at 25°C?
What is the ion product of water ($K_w$) at 25°C?
In water, what is the concentration of hydroxide ions ($OH^-$) at pH 7?
In water, what is the concentration of hydroxide ions ($OH^-$) at pH 7?
Which of the following substances is classified as a strong acid?
Which of the following substances is classified as a strong acid?
What does the term 'proton hopping' refer to?
What does the term 'proton hopping' refer to?
Which indicator dye is best for detecting pH changes in acidic solutions?
Which indicator dye is best for detecting pH changes in acidic solutions?
What is the combined equilibrium constant (Kcombined) for the reactions involving carbonic acid and bicarbonate?
What is the combined equilibrium constant (Kcombined) for the reactions involving carbonic acid and bicarbonate?
How does the addition of 1 ml of 10 N NaOH affect the pH of the buffer made from NaH2PO4 and Na2HPO4?
How does the addition of 1 ml of 10 N NaOH affect the pH of the buffer made from NaH2PO4 and Na2HPO4?
What is the ratio of HCO3- to H2CO3 in the buffer system at a pH of 7.4?
What is the ratio of HCO3- to H2CO3 in the buffer system at a pH of 7.4?
What is the expected final pH when 1 ml of 10 N NaOH is added to 1 liter of pure water with an initial pH of 7.0?
What is the expected final pH when 1 ml of 10 N NaOH is added to 1 liter of pure water with an initial pH of 7.0?
What is the value of pKa given that pKa is 6.86 in the context of the buffer system?
What is the value of pKa given that pKa is 6.86 in the context of the buffer system?
Which component of the buffer system represents the weak acid?
Which component of the buffer system represents the weak acid?
What is the concentration of OH- produced when 1 ml of 10 N NaOH is added to pure water?
What is the concentration of OH- produced when 1 ml of 10 N NaOH is added to pure water?
What is the equilibrium constant for the dissociation of carbonic acid (Ka)?
What is the equilibrium constant for the dissociation of carbonic acid (Ka)?
If the pKa of a buffer system is 6.86, what is the pH when the concentration of the conjugate base is twice that of the acid?
If the pKa of a buffer system is 6.86, what is the pH when the concentration of the conjugate base is twice that of the acid?
What effect does increasing the concentration of the conjugate base have on the buffer system's pH?
What effect does increasing the concentration of the conjugate base have on the buffer system's pH?
Study Notes
Ionization/Dissociation of Water
- Water dissociates into hydrogen ions (H+) and hydroxide ions (OH-)
- The equilibrium constant (Keq) for the dissociation of water is 1.8 x 10^-16 M
- The ion product of water (Kw) is 1 x 10^-14 M2
- In pure water at 25°C, the concentration of [H+] and [OH-] are both 1 x 10^-7 M
pH and pOH
- pH is the negative logarithm of the hydrogen ion concentration: pH = -log10[H+]
- pOH is the negative logarithm of the hydroxide ion concentration: pOH = -log10[OH-]
- The sum of pH and pOH is always 14: pH + pOH = 14
Weak Acids & Bases
- Strong acids like hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3) are completely ionized in dilute aqueous solutions.
- Strong bases like sodium hydroxide (NaOH) and potassium hydroxide (KOH) are completely ionized.
- Weak acids and bases dissociate partially in solution, with a characteristic acid dissociation constant (Ka).
- Stronger acids have a greater tendency to lose their proton.
- The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of the acid and the ratio of the concentrations of the acid and its conjugate base.
Calculating the pH of Weak Acids
- The Ka value is used to calculate the concentration of hydrogen ions ([H+])
- The pH of a weak acid solution is calculated using the Henderson-Hasselbalch equation.
Buffers
- Buffers resist changes in pH when small amounts of acid or base are added.
- A buffer system consists of a weak acid (proton donor) and its conjugate base (proton acceptor).
- The pH of a buffer solution is calculated using the Henderson-Hasselbalch equation.
Physiological Buffer Systems
- Hemoglobin is a major buffer in the blood.
- Proteins act as non-bicarbonate buffers.
- Phosphate buffer system is important for intracellular buffering.
- Carbonic acid-bicarbonate buffer system is the primary buffer system in blood.
Phosphate Buffer System
- The pKa of the phosphate buffer system is 6.86.
- The ratio of HPO42- to H2PO4- in the blood is about 4:1.
Carbonic Acid-Bicarbonate Buffer System
- The carbonic acid-bicarbonate buffer system is responsible for maintaining blood pH.
- This system involves the reversible reaction between CO2 and H2O to form carbonic acid (H2CO3).
- The pKcombined for this buffer system is 6.1.
- The ratio of HCO3- to H2CO3 in blood is about 20:1.
Questions & Answers
- Question 1: The pH of a mixture of 0.042 M NaH2PO4 and 0.058 M Na2HPO4 is 7.0.
- Question 2: Adding 1 ml of 10 N NaOH to a liter of the buffer prepared in Question 1 increases the pH by 0.2 units, to 7.2.
- Question 3: Adding 1 ml of 10 N NaOH to a liter of pure water increases the pH to 12.
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Description
Explore the concepts of water ionization, pH, and pOH through this quiz. Understand the dissociation of water and the behavior of strong and weak acids and bases. Test your knowledge on key equations and constants related to acid-base chemistry.
