Chemistry In Context
9th Edition
ISBN: 9781259638145
Author: Fahlman, Bradley D., Purvis-roberts, Kathleen, Kirk, John S., Bentley, Anne K., Daubenmire, Patrick L., ELLIS, Jamie P., Mury, Michael T., American Chemical Society
Publisher: Mcgraw-hill Education,
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Chapter 12.2, Problem 12.7YT
A practicing scientist must Judge a potential buffer for its utility in mimicking different cellular environments. Consider the list of target pH values and match them to the best possible chemical mixture for creating that pH, see Table 12.1 for a list.
- a. pH 2.5
- b. pH 7.4
- c. pH 6.8
- d. pH 5.4
Table 12.1 Dissociation of Some Weak Acids with Ka and pKa Values
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2. A solution of pH 12 will contain a large concentration of
(fill in)
a. Cl-
b. Na+
С. ОН-
d. H+
ions. Buffers are substances that keep the pH of a solution stable. In blood, the main
buffer system is carbonic acid-bicarbonate in which bicarbonate acts as the
a. H+ suppressor
b. H+ асceptor
c. H+ donor
d. H+ processor
H,CO3
HCO,-
+
Looking at the above equation we can deduct that if an acidic solution is injected in the
blood of a person, the above equilibrium will move to the
a. right
b. left
The action of buffers in the blood is important to keep the pH stable around
а. 7.4
b.7.0
с. 7.8
d. 6.8
In the human stomach, digestive enzymes require a high concentration of
a. hydroxide ions
b. protons
c. cholesterol
d.inositol
for optimal function.
1. You want to maintain pH-7.0 for an enzyme-catalyzed reaction that will produce hydroxide ions along with
the desired product. At equal concentrations, which of the following weak acids will act as a better buffer for
the reaction?
Acid A-pk. -6.5
Acid B-pk.-7.5
A. Acid A
B. Acid B
C. Water would actually be the best buffer
D. Both buffers would be equally as effective
E. Cannot be determined with the information given
Answer:
11. What is the pH of the buffer solution formed with 0.05M pyruvic acid and 0.07M
of sodium pyruvate, if Ka = 3.1x10-3?
A. 2.51
C. 2.36
D. 3.65
B. 2.65
12. What is the pH of stomach acid with 1.2 x 10-3 M HCI?
A. 2.92
C. 3.75
D. 12.29
B. 11.08
13. Which of the following concentrations is the least acidic?
A. 1.2 x 10-3
C. 1.5 x 10-3
B. 2.2 x 10-3
D. 2.8 x 10-3
Chapter 12 Solutions
Chemistry In Context
Ch. 12.1 - Skill Building Finding Equilibrium Glucose and...Ch. 12.1 - Prob. 12.3YTCh. 12.1 - Prob. 12.4YTCh. 12.2 - Prob. 12.5YTCh. 12.2 - Prob. 12.6YTCh. 12.2 - A practicing scientist must Judge a potential...Ch. 12.3 - Prob. 12.8YTCh. 12.3 - Skill Building Checking on Carbon a. Examine the...Ch. 12.3 - Prob. 12.10YTCh. 12.3 - Prob. 12.11YT
Ch. 12.3 - Prob. 12.12YTCh. 12.4 - Prob. 12.13YTCh. 12.4 - Skill Building Functional Groups in Dopamine Draw...Ch. 12.4 - Prob. 12.15YTCh. 12.5 - Prob. 12.16YTCh. 12.5 - Prob. 12.17YTCh. 12.6 - Prob. 12.18YTCh. 12.6 - Prob. 12.19YTCh. 12.6 - The structures of proteins, such as the ones shown...Ch. 12.7 - Reconsider your work in past chapters. List three...Ch. 12.7 - Prob. 12.22YTCh. 12.7 - Prob. 12.23YTCh. 12.8 - Prob. 12.24YTCh. 12.8 - Prob. 12.25YTCh. 12.9 - Skill Building Ester Formation Draw structural...Ch. 12.9 - Prob. 12.27YTCh. 12.9 - You Decide Supersize My Aspirin A friend who...Ch. 12.9 - Modern methods of drug discovery involve...Ch. 12.10 - Make two lists of drugs for each of the two...Ch. 12.10 - See for yourself the shapes of drug molecules by...Ch. 12.10 - Prob. 12.33YTCh. 12.10 - Prob. 12.34YTCh. 12 - Scientific Practices Follow the Hormone Using the...Ch. 12 - The field of chemistry has many sub-disciplines....Ch. 12 - Prob. 2QCh. 12 - Prob. 4QCh. 12 - Nitrous acid (HNO2) has a Ka value of 4.0 10 4,...Ch. 12 - Use the Henderson-Hasselbalch equation and Table...Ch. 12 - Write the structural formula and line-angle...Ch. 12 - Prob. 8QCh. 12 - Prob. 9QCh. 12 - Prob. 10QCh. 12 - Prob. 11QCh. 12 - Prob. 12QCh. 12 - Estradiol is relatively insoluble in water but...Ch. 12 - Prob. 14QCh. 12 - Prob. 15QCh. 12 - Prob. 16QCh. 12 - Define and relate the two terms: hormone and...Ch. 12 - Refer to Figure 11.17. Select two examples of...Ch. 12 - Prob. 19QCh. 12 - Molecules as diverse as cholesterol, sex hormones,...Ch. 12 - Prob. 21QCh. 12 - Prob. 22QCh. 12 - Prob. 23QCh. 12 - Sulfanilamide is the simplest sulfa drug, a type...Ch. 12 - Explain why an equilibrium constant cannot tell...Ch. 12 - Use the information in Table 12.1 to redraw Figure...Ch. 12 - Draw structural formulas for each of these...Ch. 12 - In Your Turn 12.12, you were asked to draw...Ch. 12 - Prob. 29QCh. 12 - Prob. 30QCh. 12 - Prob. 31QCh. 12 - Prob. 32QCh. 12 - Prob. 34QCh. 12 - Prob. 35QCh. 12 - Prob. 36QCh. 12 - Prob. 37QCh. 12 - Prob. 38QCh. 12 - The text states that some racemic mixtures contain...Ch. 12 - Prob. 40QCh. 12 - Prob. 41QCh. 12 - Prob. 44QCh. 12 - Prob. 47QCh. 12 - Prob. 49QCh. 12 - Dorothy Crowfoot Hodgkin first determined the...Ch. 12 - Prob. 52Q
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- 3. You want to make a pH=10.5 buffer using methylamine (CH;NH2) and its conjugate acid methylammonium (pKa 10.632). a. Write the balanced chemical equation showing how this buffer would neutralize strong acid. b. Write the balanced chemical equation showing how this buffer would neutralize strong base. c. Use the concepts from those two reactions and at least one more balanced chemical equation to explain why buffers work. d. Should buffers be prepared at high or low concentration? Why?arrow_forward4. A 100 mL buffer solution with pH of 4.80 is prepared as a stock solution. Using this stock buffer solution, three buffers are prepared by diluting a given volume of the stock buffer (as shown below) to 100 mL with water. Buffer 1 a. b. e a. E Do they have the same pH? Check the box corresponding your answer. Yes No Which is true about their absolute concentrations? Check the box corresponding your answer. [Buffer 1]> [Buffer 2] > [Buffer 3) [Buffer 3] > [Buffer 2]> [Buffer 1] [Buffer 3] = [Buffer 2] = [Buffer 1) [Buffer 3] = [Buffer 2] > [Buffer 1) [Buffer 3] > [Buffer 2] = [Buffer 1) d. Which of the following is true about the ability of the three buffers to resist pH change when 1 mL of HCI is added to each buffer? Check the box corresponding your answer. Which is true about their concentration ratios? Check the box corresponding your answer. [Buffer 1]> [Buffer 2] > [Buffer 3) [Buffer 3] > [Buffer 2]> [Buffer 1) [Buffer 3] = [Buffer 2] = [Buffer 1) Solution A B C D [Buffer 3] =…arrow_forward17. What is the pH of the solution produced when 50 mL of 0.25 M HCl is added to 250.0 mL of 0.1 M ammonia? [Given pKa of NH4 is 9.245] a. 4.755 b. 8.944 C. 9.245 d. 9.546arrow_forward
- 11.The pKa of a weak acid was determined by measuring the pH of a solution containing the weak acid at 0.40 M and its conjugate base at 0.60 M. The measured pH was 7.8. What is the pKa of the weak acid? a. 8.0 b. 7.8 c. 7.6 d. 7.0 e. 7.4arrow_forwardWhat is the pH of a buffer solution in which the molar concentration of acetic acid is 0.15M and the molar mass concentration of the acetate ion is 0.55M? ka(acetic acid)=1.8 x 10-5 a. 5.30 b. 12.93 c. 5.01 d. 4.74arrow_forwardThe pH of a buffer that contains 1.100 M NH3 and 1.300 M NH4+ is 9.17. What would be the new pH if a 100 mL portion of 0.075 M HCl is added to another 400 mL portion of the buffer? a. 9.15 b. 9.17 c. 9.18arrow_forward
- 1) Buffers are mixtures of A. Strong acid and strong base B. Strong acid and weak base C. Weak acid and their conjugate base D. Weak base and their conjugate acid 2) If a solution has to be a buffer, its pH should be a buffer, it's pH should be A. At 7 B. At 14 C. At is Ka value D. At its pka value 3) What is the pH of a solution composed of 0.20 M NH3 and 0.15 M NH&CI? A. 2.15 С. 8.26 B. 4.62 D. 9.38 4) Which of the following is the correct representation of Henderson – Hasselbalch equation? А. С. [A] pH = pKa+ log- [HA] [proton donor] pH = pK. - log [proton acceptor] B. pH = pk, + log= [proton acceptor] [proton donor] D. All of the above 5) According to Henderson-Hasselbalch equation, when the pH of a solution becomes equal to its pKa, the solution becomes a buffer This condition is achieved when A. Concentration of proton donor become zero. B. Concentration of proton acceptor become zero. C. The concentration of proton donor equals the concentration of proton acceptor. D. The…arrow_forward21.Acetic acid has a pKa of 4.8. How many milliliters of 0.2 M acetic acid and 0.1 sodium acetate are required to prepare 1 liter of 0.1 M buffer solution having a pH of 4.8? A. 500 ml acetic acid and 500 ml sodium acetate B. 250 ml acetic acid and 250 ml sodium acetate, then 500 ml water C. 250 ml acetic acid and 500 ml sodium acetate, then 250 ml water D. 500 ml acetic acid and 250 ml sodium acetate, then 250 ml water E. None of the above 22. The pKa value of phosphoric acid are 2.2, 7.2 and 12.7. A phosphate buffer of pH = 7.4 can be prepared using 2- A. H₂PO4 and HPO4² 3- B. HPO4² and PO4³- C. H3PO4 and HCI D. None of the abovearrow_forwardAnswer the following questions based on the graph below. pH-log solubility 1 2 4 10 6 8 pH 12 14 15. Why type of a drug classification can be assumed for a drug that demonstrates this type of a pH- solubility profile? a. WA b. WB c. NE 16. What is the approximate pka of this drug? а. 2 b. 6 C. 10 d. 12 17. What is the log S, for this drug? а. О.7 b. 1.4 c. 3.2 d. 4.3 log solubilityarrow_forward
- 1. A buffer solution is prepared by taking 0.25 moles of acetic acid (pKa = 4.76) and 0.400 moles of barium acetate in sufficient water to make 1.400 liters of solution. Calculate the pH of this solution. a. 4.25 b. 4.45 c. 5.00 d. 5.27 e. 5.35 2. You have 500.0 mL of a buffer solution containing 0.30M acetic acid and 0.20M sodium acetate. What will be the pH of this solution after the addition of 20.0mL of 1.00M HCl solution? (Ka = 1.8 x 10^ -5). a. 4.74 b. 5.07 c. 4.00 d. 3.02 e. 4.42 3. 40.0mL of 0.10M HCl was added to 50.0 mL of 0.10M NaOH and the mixture was stirred, then tested with a pH meter. What is its pH at 25.0 C? a. 1.96 b. 2.00 c. 7.00 d. 11.90 e. 12.05arrow_forward8. What is a buffer? 9. Predict the products of the following acid-base reaction: NH3 (ag) + HNO; (ag) → а. NH2OH (aя) b. NHẠNO3 (ag) с. NH,ОH (ag) d. no reaction takes place > Answer and brief explanation: 10. What effect will addition of sodium acetate have on the pH of a solution of acetic acid? a. increase the pH b. decrease the pH C. no effect d. cannot tell from information given > Answer and brief explanation:arrow_forwardA buffer solution is prepared in which the concentration of NH3 is 0.20 M and the concentration of NH4* is 0.30 M. What is the pH of this solution? The equilibrium constant, Ka for NH,1+ equals 5.56 x 10-10. А. 8.73 В. 9.08 С. 9.43 D. 11.72arrow_forward
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