Textbook Question
In what volume ratio should you mix 1.0 M solutions of NH4Cl and NH3 to produce a buffer solution having pH = 9.80?
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Ch.17 - Applications of Aqueous Equilibria
Chapter 17, Problem 78
Which of the following conjugate acid–base pairs should you choose to prepare a buffer solution that has pH = 4.50? Explain. (a) HSO4- and SO42- (b) HOCl and OCl- (c) C6H5CO2H and C6H5CO2-.
Verified step by step guidance1
Step 1: Understand that a buffer solution is most effective when the pH is close to the pKa of the weak acid in the conjugate acid-base pair.
Step 2: Identify the pKa values for each weak acid in the given pairs: (a) HSO4- has a pKa around 1.99, (b) HOCl has a pKa around 7.46, and (c) C6H5CO2H (benzoic acid) has a pKa around 4.20.
Step 3: Compare the pKa values to the desired pH of 4.50. The best buffer system will have a pKa value closest to 4.50.
Step 4: Recognize that the pKa of C6H5CO2H (4.20) is closest to the desired pH of 4.50, making it the most suitable choice for the buffer solution.
Step 5: Conclude that the conjugate acid-base pair C6H5CO2H and C6H5CO2- is the best choice for preparing a buffer solution with a pH of 4.50.
Related Practice
Textbook Question
Give a recipe for preparing a CH3CO2H-CH3CO2Na buffer solution that has pH = 4.44.
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Textbook Question
You need a buffer solution that has pH = 7.00. Which of the following buffer systems should you choose? Explain.
(a) H3PO4 and H2PO4 -
(b) H2PO4- and HPO42-
(c) HPO42- and PO43-
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Textbook Question
Consider a buffer solution that contains equal concentrations of H2PO4- and HPO42-. Will the pH increase, decrease, or remain the same when each of the following substances is added? (a) Na2HPO4 (b) HBr (c) KOH (d) KI (e) H3PO4 (f) Na3PO4
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Textbook Question
Consider the titration of 60.0 mL of 0.150 M HNO3 with 0.450 M NaOH.
(a) How many millimoles of HNO3 are present at the start of the titration?
(b) How many milliliters of NaOH are required to reach the equivalence point?
(c) What is the pH at the equivalence point?
(d) Sketch the general shape of the pH titration curve.
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Textbook Question
Make a rough plot of pH versus milliliters of acid added for the titration of 50.0 mL of 1.0 M NaOH with 1.0 M HCl. Indicate the pH at the following points, and tell how many milliliters of acid are required to reach the equivalence point.
(a) At the start of the titration
(b) At the equivalence point
(c) After the addition of a large excess of acid
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