Chemistry
9th Edition
ISBN: 9781133611097
Author: Steven S. Zumdahl
Publisher: Cengage Learning
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Textbook Question
Chapter 15, Problem 6ALQ
Sketch a pH curve for the titration of a weak acid (HA) with a strong base (NaOH). List the major species, and explain how you would go about calculating the pH of the solution at various points, including the halfway point and the equivalence point.
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Let's say that you're titrating an acid with a sodium hydroxide solution, and you think you're at the equivalence point (when acid moles = base moles). You (or your partner, I guess) accidentally add an extra drop of base, and the solution immediately turns dark pink. Oh no! Why does the color's intensity change so drastically?
a) Sodium Hydroxide is a strong base, so adding any extra amount will dramatically decrease the pH, thus forcing the indicator to turn dark pink.
b) Sodium Hydroxide is a strong acid, so adding any extra amount will dramatically decrease the pH, thus forcing the indicator to turn dark pink.
c) Sodium Hydroxide is a strong base, so adding any extra amount will dramatically increase the pH, thus forcing the indicator to turn dark pink.
d) Sodium Hydroxide is a strong acid, so adding any extra amount will dramatically increase the pH, thus forcing the indicator to turn dark pink.
You have a 15 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 8.06. You incubate
this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid
dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has
decreased to 5.91. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in
the original 15 mL sample.
O=
CH3
Acetylcholine
H₂O
CH,—C−O−CH,—CH,—*N-CH, → HO−CH,—CH,—*N–CH, + CH,—C−O + H*
CH3
CH 3
Choline
CH3
Acetate
You have a 18 mL sample of acetylcholine (a neurotransmitter) with an unknown concentration and a pH of 8.35. You incubate this sample with the enzyme acetylcholinesterase to convert all of the acetylcholine to choline and acetic acid. The acetic acid dissociates to yield acetate and hydrogen ions. At the end of the incubation period, you measure the pH again and find that it has decreased to 6.03. Assuming there was no buffer in the assay mixture, determine the number of nanomoles of acetylcholine in the original 18 mL sample.
Chapter 15 Solutions
Chemistry
Ch. 15 - What is meant by the presence of a common ion? How...Ch. 15 - Define a buffer solution. What makes up a buffer...Ch. 15 - One of the most challenging parts of solving...Ch. 15 - A good buffer generally contains relatively equal...Ch. 15 - Draw the general titration curve for a strong acid...Ch. 15 - Instead of the titration of a strong acid by a...Ch. 15 - Sketch the titration curve for a weak acid...Ch. 15 - Sketch the titration curve for a weak base...Ch. 15 - What is an acidbase indicator? Define the...Ch. 15 - Why does an indicator change from its acid color...
Ch. 15 - What are the major species in solution after...Ch. 15 - A friend asks the following: Consider a buffered...Ch. 15 - Mixing together solutions of acetic acid and...Ch. 15 - Could a buffered solution be made by mixing...Ch. 15 - Sketch two pH curves, one for the titration of a...Ch. 15 - Sketch a pH curve for the titration of a weak acid...Ch. 15 - You have a solution of the weak acid HA and add...Ch. 15 - You have a solution of the weak acid HA and add...Ch. 15 - The common ion effect for weak acids is to...Ch. 15 - Prob. 10QCh. 15 - A best buffer has about equal quantities of weak...Ch. 15 - Consider the following pH curves for 100.0 mL of...Ch. 15 - An acid is titrated with NaOH. The following...Ch. 15 - Consider the following four titrations. i. 100.0...Ch. 15 - Figure 14-4 shows the pH curves for the titrations...Ch. 15 - Acidbase indicators mark the end point of...Ch. 15 - How many of the following are buffered solutions?...Ch. 15 - Which of the following can be classified as buffer...Ch. 15 - A certain buffer is made by dissolving NaHCO3 and...Ch. 15 - A buffer is prepared by dissolving HONH2 and...Ch. 15 - Calculate the pH of each of the following...Ch. 15 - Calculate the pH of each of the following...Ch. 15 - Compare the percent dissociation of the acid in...Ch. 15 - Compare the percent ionization of the base in...Ch. 15 - Calculate the pH after 0.020 mole of HCl is added...Ch. 15 - Calculate the pH after 0.020 mole of HCl is added...Ch. 15 - Calculate the pH after 0.020 mole of NaOH is added...Ch. 15 - Calculate the pH after 0.020 mole of NaOH is added...Ch. 15 - Which of the solutions in Exercise 21 shows the...Ch. 15 - Prob. 30ECh. 15 - Calculate the pH of a solution that is 1.00 M HNO2...Ch. 15 - Calculate the pH of a solution that is 0.60 M HF...Ch. 15 - Calculate the pH after 0.10 mole of NaOH is added...Ch. 15 - Calculate the pH after 0.10 mole of NaOH is added...Ch. 15 - Calculate the pH of each of the following buffered...Ch. 15 - Calculate the pH of each of the following buffered...Ch. 15 - Calculate the pH of a buffered solution prepared...Ch. 15 - A buffered solution is made by adding 50.0 g NH4Cl...Ch. 15 - Calculate the pH after 0.010 mole of gaseous HCl...Ch. 15 - An aqueous solution contains dissolved C6H5NH3Cl...Ch. 15 - Calculate the mass of sodium acetate that must be...Ch. 15 - What volumes of 0.50 M HNO2 and 0.50 M NaNO2 must...Ch. 15 - Consider a solution that contains both C5H5N and...Ch. 15 - Calculate the ratio [NH3]/[NH4+] in...Ch. 15 - Carbonate buffers are important in regulating the...Ch. 15 - When a person exercises, muscle contractions...Ch. 15 - Consider the acids in Table 13-2. Which acid would...Ch. 15 - Consider the bases in Table 13-3. Which base would...Ch. 15 - Calculate the pH of a solution that is 0.40 M...Ch. 15 - Calculate the pH of a solution that is 0.20 M HOCl...Ch. 15 - Which of the following mixtures would result in...Ch. 15 - Which of the following mixtures would result in a...Ch. 15 - What quantity (moles) of NaOH must be added to 1.0...Ch. 15 - Calculate the number of moles of HCl(g) that must...Ch. 15 - Consider the titration of a generic weak acid HA...Ch. 15 - Sketch the titration curve for the titration of a...Ch. 15 - Consider the titration of 40.0 mL of 0.200 M HClO4...Ch. 15 - Consider the titration of 80.0 mL of 0.100 M...Ch. 15 - Consider the titration of 100.0 mL of 0.200 M...Ch. 15 - Consider the titration of 100.0 mL of 0.100 M...Ch. 15 - Lactic acid is a common by-product of cellular...Ch. 15 - Repeat the procedure in Exercise 61, but for the...Ch. 15 - Repeat the procedure in Exercise 61, but for the...Ch. 15 - Repeat the procedure in Exercise 61, but for the...Ch. 15 - Calculate the pH at the halfway point and at the...Ch. 15 - In the titration of 50.0 mL of 1.0 M methylamine,...Ch. 15 - You have 75.0 mL of 0.10 M HA. After adding 30.0...Ch. 15 - A student dissolves 0.0100 mole of an unknown weak...Ch. 15 - Two drops of indicator HIn (Ka = 1.0 109), where...Ch. 15 - Methyl red has the following structure: It...Ch. 15 - Potassium hydrogen phthalate, known as KHP (molar...Ch. 15 - A certain indicator HIn has a pKa of 3.00 and a...Ch. 15 - Which of the indicators in Fig. 14-8 could be used...Ch. 15 - Prob. 74ECh. 15 - Which of the indicators in Fig. 14-8 could be used...Ch. 15 - Prob. 76ECh. 15 - Estimate the pH of a solution in which bromcresol...Ch. 15 - Estimate the pH of a solution in which crystal...Ch. 15 - A solution has a pH of 7.0. What would be the...Ch. 15 - A solution has a pH of 4.5. What would be the...Ch. 15 - Derive an equation analogous to the...Ch. 15 - a. Calculate the pH of a buffered solution that is...Ch. 15 - Tris(hydroxymethyl)aminomethane, commonly called...Ch. 15 - You make 1.00 L of a buffered solution (pH = 4.00)...Ch. 15 - You have the following reagents on hand: Solids...Ch. 15 - Prob. 86AECh. 15 - Phosphate buffers are important in regulating the...Ch. 15 - What quantity (moles) of HCl(g) must be added to...Ch. 15 - Prob. 89AECh. 15 - The following plot shows the pH curves for the...Ch. 15 - Calculate the volume of 1.50 102 M NaOH that must...Ch. 15 - Prob. 92AECh. 15 - A certain acetic acid solution has pH = 2.68....Ch. 15 - A 0.210-g sample of an acid (molar mass = 192...Ch. 15 - The active ingredient in aspirin is...Ch. 15 - One method for determining the purity of aspirin...Ch. 15 - A student intends to titrate a solution of a weak...Ch. 15 - A student titrates an unknown weak acid, HA, to a...Ch. 15 - A sample of a certain monoprotic weak acid was...Ch. 15 - Consider 1.0 L of a solution that is 0.85 M HOC6H5...Ch. 15 - What concentration of NH4Cl is necessary to buffer...Ch. 15 - Consider the following acids and bases: HCO2H Ka =...Ch. 15 - Consider a buffered solution containing CH3NH3Cl...Ch. 15 - Consider the titration of 150.0 mL of 0.100 M HI...Ch. 15 - Consider the titration of 100.0 mL of 0.100 M HCN...Ch. 15 - Consider the titration of 100.0 mL of 0.200 M...Ch. 15 - Consider the following four titrations (iiv): i....Ch. 15 - Another way to treat data from a pH titration is...Ch. 15 - A buffer is made using 45.0 mL of 0.750 M HC3H5O2...Ch. 15 - A 0.400-M solution of ammonia was titrated with...Ch. 15 - What volume of 0.0100 M NaOH must be added to 1.00...Ch. 15 - Consider a solution formed by mixing 50.0 mL of...Ch. 15 - When a diprotic acid. H2A. is titrated with NaOH,...Ch. 15 - Prob. 114CPCh. 15 - The titration of Na2CO3 with HCl bas the following...Ch. 15 - Consider the titration curve in Exercise 115 for...Ch. 15 - A few drops of each of the indicators shown in the...Ch. 15 - Malonic acid (HO2CCH2CO2H) is a diprotic acid. In...Ch. 15 - A buffer solution is prepared by mixing 75.0 mL of...Ch. 15 - A 10.00-g sample of the ionic compound NaA, where...Ch. 15 - Calculate the pH of a solution prepared by mixing...Ch. 15 - Consider a solution prepared by mixing the...
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