2. Joey was tasked to ensure that an enzyme responsible for keeping his species from extinction remains biologically active. To do so, he needs to store it in a buffer solution with a pH of 10.00. Unfortunately, only three buffer systems are available in their laboratory: Buffer System Weak Acid Component K Conjugate Base Salt KYA Benzoic acid, CH,COOH 6.25 x 10 NaC H₂COO MUH Boric acid, H₂BO 5.81 x 10 NaH₂BO TWO Hydrogen cyanide, HCN 6.20 X 100 NaCN A. In what buffer system (KYA, MUH, or TWO) will Joey store the enzyme? In your solution sheet, show calculations and briefly explain to support your answer. B. Write the equilibrium reaction involved in the buffer system. Write your answer on your solution sheet C. Calculate the amount (in mL) of the 1.75 M stock solution (pH 7.00) of the same buffer system needed to prepare 250 mL of a 0.550 M buffer pH 7.00.

2. Joey was tasked to ensure that an enzyme responsible for keeping his species from extinction remains biologically active. To do so, he needs to store it in a buffer solution with a pH of 10.00. Unfortunately, only three buffer systems are available in their laboratory: Buffer System Weak Acid Component K Conjugate Base Salt KYA Benzoic acid, CH,COOH 6.25 x 10 NaC H₂COO MUH Boric acid, H₂BO 5.81 x 10 NaH₂BO TWO Hydrogen cyanide, HCN 6.20 X 100 NaCN A. In what buffer system (KYA, MUH, or TWO) will Joey store the enzyme? In your solution sheet, show calculations and briefly explain to support your answer. B. Write the equilibrium reaction involved in the buffer system. Write your answer on your solution sheet C. Calculate the amount (in mL) of the 1.75 M stock solution (pH 7.00) of the same buffer system needed to prepare 250 mL of a 0.550 M buffer pH 7.00.

Chemistry: An Atoms First Approach

2nd Edition

ISBN:9781305079243

Author:Steven S. Zumdahl, Susan A. Zumdahl

Publisher:Steven S. Zumdahl, Susan A. Zumdahl

Chapter14: Acid- Base Equilibria

Section: Chapter Questions

Problem 4RQ: A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If...

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Enough water is added to the buffer in Question 29 to make the total volume 10.0 L. Calculate (a) the pH of the buffer. (b) the pH of the buffer after the addition of 0.0500 mol of HCl to 0.600 L of diluted buffer. (c) the pH of the buffer after the addition of 0.0500 mol of NaOH to 0.600 L of diluted buffer. (d) Compare your answers to Question 29(a)-(c) with your answers to (a)-(c) in this problem. (e) Comment on the effect of dilution on the pH of a buffer and on its buffer capacity.
A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If you wanted to buffer a solution at pH = 4.00 or pH = 10.00, how would you decide which weak acidconjugate base or weak baseconjugate acid pair to use? The second characteristic of a good buffer is good buffering capacity. What is the capacity of a buffer? How do the following buffers differ in capacity? How do they differ in pH? 0.01 M acetic acid/0.01 M sodium acetate 0.1 M acetic acid/0.1 M sodium acetate 1.0 M acetic acid/1.0 M sodium acetate
Determine the dominant acid-base equilibrium that results when each of the following pairs of solutions is mixed. Indicate the equilibrium by writing 1 for a strong acid, 3 for a weak acid, 4 for an acidic buffer, 7 for a neutral solution, 10 for a basic buffer, 11 for a weak base, and 13 for a strong base. (a) 10.0 mL of 0.15 M NaOH + 15.0 mL of 0.10 M HNO3 (b) 25.0 mL of 0.10 M HCl + 10.0 mL of 0.25 M NH3 (c) 50.0 mL of 0.050 M NaOH + 50.0 mL of 0.10 M NH3 (d) 50.0 mL of 0.10 M NH3 + 50.0 mL of 0.05 M HCl
What is the pH of a buffer that is 0.175 M in a weak acid and 0.200 M in the acids conjugate base? The acids ionization constant is 5.7 104.
Ammonia gas is bubbled into 275 mL of water to make an aqueous solution of ammonia. To prepare a buffer with a pH of 9.56, 15.0 g of NH4Cl are added. How many liters of NH3; at 25C and 0.981 atm should be used to prepare the buffer? Assume no volume changes and ignore the vapor pressure of water.
Ka for formic acid is 1.7 104 at 25C. A buffer is made by mixing 529 mL of 0.465 M formic acid, HCHO2, and 494 mL of 0.524 M sodium formate, NaCHO2. Calculate the pH of this solution at 25C after 110 mL of 0.152 M HCl has been added to this buffer.
When 40.00 mL of a weak monoprotic acid solution is titrated with 0.100-M NaOH, the equivalence point is reached when 35.00 mL base has been added. After 20.00 mL NaOH solution has been added, the titration mixture has a pH of 5.75. Calculate the ionization constant of the acid.
Choose a weak-acid/weak-base conjugate pair from which you could prepare a buffer solution with pH = 7.5. Explain how you chose the conjugate pair. Calculate the ratio [weak base]/[weak acid) required to give pH = 7.5.
A buffer is prepared using the butyric acid/butyrate (HC4H7O2/C4H7O2)acid-base pair. The ratio of acid to base is 2.2 and Ka for butyric acid is1.54105. (a) What is the pH of this buffer? (b) Enough strong base is added to convert 15% of butyric acid to the butyrate ion. What is the pH of the resulting solution? (c) Strong acid is added to the buffer to increase its pH. What must the acid/base ratio be so that the pH increases by exactly one unit (e.g., from 2 to 3) from the answer in (a)?
Isocyanic acid (HNCO) can be prepared by heating sodium cyanate in the presence of solid oxalic acid according to the equation 2NaOCN(s)+H2C2O4(s)2HNCO(l)+Na2C2O4(s) Upon isolating pure HNCO(l), an aqueous solution of HNCO can be prepared by dissolving the liquid HNCO in water. What is the pH of a l00.-mL solution of HNCO prepared from the reaction of 10.0 g each of NaOCN and H2C2O4, assuming all of the HNCO produced is dissolved in solution? (Ka of HNCO = 1.2 l04.)
The pigment cyanidin aglycone is one of the anthocyanin molecules that gives red cabbage (Brassica oleracea var. capitata f. rubra) its characteristic red coloration. Many chemistry students have used this red cabbage indicator to study acid-base chemistry. Estimate tire pH range at which cyanidin agly-cone shows a color change. Anth-H(aq) Anth(aq) + H+ (aq) Ka = 1.3 107
Using the diagrams shown in Problem 10-117, which of the solutions would have the greatest buffer capacity, that is, greatest protection against pH change, when the following occurs? a. A strong acid is added to the solution. b. A strong base is added to the solution.