5 A chemistry graduate student is given 450. mL of a 0.10M ammonia (NH3) solution. Ammonia is a weak base with K, = 1.8 × 10. What mass of NH4Cl should the student dissolve in the NH3 solution to turn it into a buffer with pH = 9.11? You may assume that the volume of the solution doesn't change when the NH4Cl is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits. ☐ ☐ x10

5 A chemistry graduate student is given 450. mL of a 0.10M ammonia (NH3) solution. Ammonia is a weak base with K, = 1.8 × 10. What mass of NH4Cl should the student dissolve in the NH3 solution to turn it into a buffer with pH = 9.11? You may assume that the volume of the solution doesn't change when the NH4Cl is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits. ☐ ☐ x10

Chemistry: Principles and Reactions

8th Edition

ISBN:9781305079373

Author:William L. Masterton, Cecile N. Hurley

Publisher:William L. Masterton, Cecile N. Hurley

Chapter14: Equilibria In Acid-base Solutions

Section: Chapter Questions

Problem 52QAP: A solution is prepared by dissolving 0.350 g of benzoic acid, HC7H5O2, in water to make 100.0 mL of...

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What is the pH of a buffer that is 0.150 M in a weak acid and 0.150 M in the acids conjugate base? The acids ionization constant is 6.8 106.
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.
Phenol, C6H5OH, is a weak organic acid. Suppose 0.515 g of the compound is dissolved in enough water to make 125 mL of solution. The resulting solution is titrated with 0.123 M NaOH. C6H5OH(aq) + OH(aq) C6H5O(aq) + H2O() (a) What is the pH of the original solution of phenol? (b) What are the concentrations of all of the following ions at the equivalence point: Na+, H3O+, OH, and C6H5O? (c) What is the pH of the solution at the equivalence point?
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.
Does the pH of the solution increase, decrease, or stay the same when you (a) Add solid sodium oxalate, Na2C2O4, to 50.0 mL of 0.015-M oxalic acid? (b) Add solid ammonium chloride to 100. mL of 0.016-M HCl? (c) Add 20.0 g NaCl to 1.0 L of 0.012-M sodium acetate, NaCH3COO?
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Morphine, C17H19O3N, is a weak base (K b =7.4107). Consider its titration with hydrochloric acid. In the titration, 50.0 mL of a 0.1500 M solution of morphine is titrated with 0.1045 M HCl. (a) Write a balanced net ionic equation for the reaction that takes place during titration. (b) What are the species present at the equivalence point? (c) What volume of hydrochloric acid is required to reach the equivalence point? (d) What is the pH of the solution before any HCl is added? (e) What is the pH of the solution halfway to the equivalence point? (f) What is the pH of the solution at the equivalence point?
Briefly describe how a buffer solution can control the pH of a solution when strong acid is added and when strong base is added. Use NH3/NH4Cl as an example of a buffer and HCl and NaOH as the strong acid and strong base.
The composition diagram, or alpha plot, for the important acid-base system of carbonic acid, H2CO3, is illustrated. (See Study Question 1.7 for more information on such diagrams.) (a) Explain why the fraction of bicarbonate ion, HCO3, rises and then falls as the pH increases. (b) What is the composition of the solution when the pH is 6.0? When the pH is 10.0? (c) If you wanted to buffer a solution at a pH of 11.0, what should be the ratio of HCO3 to CO32?
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