Question 6 QUESTION 6Which of the following statements about buffers is (are) true?O (a) the pH of a buffered solution remains unchanged no matter how much acid or base isadded to the solution.(b) the strongest buffers are made up of strong acids and strong bases(c) a buffer composed of a weak acid of pKa = 5 is a better buffer at pH 4 than at pH 6.00(d) when pH = pKa, the weak acid and conjugate base concentrations in a buffer are equal(e) both (b) and (d)QUESTION 7Which of the following molecules cannot exhibit intermolecular (among the nselves) hydrogen bonding?ammoniaO hydrogen sulfideO flourine gasO ethanolO butanolQUESTION 8The titration of a weak monoprotic acid by NAOH is shown here. The optimal buffering capacity of this acid is expected at around pH:Click Save and Submit to save and submit. Click Save All Answers to save all answers

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Which of the following statements about buffers is (are) true? O (a) the pH of a buffered solution remains unchanged no matter how much acid or base is added to the solution. (b) the strongest buffers are made up of strong acids and strong bases (c) a buffer composed of a weak acid of pKa = 5 is a better buffer at pH 4 than at pH 6.00 (d) when pH = pka, the weak acid and conjugate base concentrations in a buffer are equal %3D (e) both (b) and (d)

Which of the following statements about buffers is (are) true? O (a) the pH of a buffered solution remains unchanged no matter how much acid or base is added to the solution. (b) the strongest buffers are made up of strong acids and strong bases (c) a buffer composed of a weak acid of pKa = 5 is a better buffer at pH 4 than at pH 6.00 (d) when pH = pka, the weak acid and conjugate base concentrations in a buffer are equal %3D (e) both (b) and (d)

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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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.
A buffer is prepared by dissolving 0.0250 mol of sodium nitrite, NaNO2, in 250.0 mL of 0.0410 M nitrous acid, HNO2. Assume no volume change after HNO2 is dissolved. Calculate the pH of this buffer.
You want to make a buffer with a pH of 10.00 from NH4+/NH3. (a) What must the [ NH4+ ]/[ NH3 ]ratio be? (b) How many moles of NH4Cl must be added to 465 mL of an aqueous solution of 1.24 M NH3 to give this pH? (c) How many milliliters of 0.236 M NH3 must be added to 2.08 g of NH4Cl to give this pH? (d) What volume of 0.499 M NH3 must be added to 395 mL, of 0.109 M NH4Cl to give this pH?
Sketch two pH curves, one for the titration of a weak acid with a strong base and one for a strong acid with a strong base. How are they similar? How are they different? Account for the similarities and the differences.
8-94 Suppose you wish to make a buffer whose pH is 8.21. You have available 1 L of 0.100 M NaH2PO4 and solid Na2HPO4. How many grams of the solid Na2HPO4 must be added to the stock solution to accomplish this task? (Assume that the volume remains 1 L.)
A buffer is prepared in which the ratio [ H2PO4 ]/[ HPO42 ]is 3.0. (a) What is the pH of this buffer? (b) Enough strong acid is added to convert 15% of HPO42- to H2PO4-. What is the pH of the resulting solution? (c) Enough strong base is added to make the pH 7.00. What is the ratio of [H2PO4-] to [HPO42-] at this point?
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The species called glacial acetic acid is 98% acetic acid by mass (d=1.0542g/mL). What volume of glacial acetic acid must be added to 100.0 mL of 1.25 M NaOH to give a buffer with a pH of 4.20?
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Sketch the titration curve for a weak acid titrated by a strong base. When performing calculations concerning weak acidstrong base titrations, the general two-slep procedure is to solve a stoichiometry problem first, then to solve an equilibrium problem to determine the pH. What reaction takes place in the stoichiometry part of the problem? What is assumed about this reaction? At the various points in your titration curve, list the major species present after the strong base (NaOH, for example) reacts to completion with the weak acid, HA. What equilibrium problem would you solve at the various points in your titration curve to calculate the pH? Why is pH 7.0 at the equivalence point of a weak acid-strong base titration? Does the pH at the halfway point to equivalence have to be less than 7.0? What does the pH at the halfway point equal? Compare and contrast the titration curves for a strong acidstrong base titration and a weak acidstrong base titration.
A sodium hydrogen carbonate-sodium carbonate buffer is to be prepared with a pH of 9.40. (a) What must the [ HCO3 ]/[ CO32 ]ratio be? (b) How many moles of sodium hydrogen carbonate must be added to a liter of 0.225 M Na2CO3 to give this pH? (c) How many grams of sodium carbonate must be added to 475 mL of 0.336 M NaHCO3 to give this pH? (Assume no volume change.) (d) What volume of 0.200 M NaHCO3 must be added to 735 mL of a 0.139 M solution of Na2CO3 to give this pH? (Assume that volumes are additive.)
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