Unit 13: Buffers And 2 Mini-labs Lecture Presentation Unit 13: Buffers And 2 Mini-labs © 2015 Pearson Education, Inc.

WARM UP TAKE OUT: Lab Notebook BE READY: To hear about your tasks for each mini-lab TIME: 1 minute

Agenda Distillation Demo Mini-Lab: Properties of Buffers Mini-Lab: Paper Chromatography

Mini-Labs COMPLETE: Both Mini-Labs TIME: Until 9:35 WHEN DONE: With both labs, attempt post-lab questions and additional buffer practice problems

Adding bromide ion to a saturated aqueous solution of _______ decreases its solubility in water. BaSO4 Li2CO3 PbS d. AgBr Answer: d

HCl and KCl HNO3 and KNO3 HCl and NH4Cl d. NH3 and NH4Cl Which of the following mixtures could be used to prepare an effective buffer solution? HCl and KCl HNO3 and KNO3 HCl and NH4Cl d. NH3 and NH4Cl Answer: d

Which solution has the greatest buffer capacity? 1 L of solution containing 0.1 M NH3 and 0.1 M NH4Cl 1 L of solution containing 0.05 M NH3 and 0.05 M NH4Cl 1 L of solution containing 0.1 M NH3 and 0.01 M NH4Cl d. 1 L of solution containing 0.5 M NH3 and 0.5 M NH4Cl Answer: d

Select the best acid or base to pair with its conjugate salt to prepare a buffer with pH ≈ 8.5. acetic acid, Ka = 1.8 x 10−5 ammonia, Kb = 1.8 x 10−5 hydroxylamine, Kb = 1.1 x 10−8 citric acid, Ka = 7.4 x 10−4 Answer: c

For HCN, Ka = 4.9  10−10. What is the pH of a buffer solution in which [HCN] = 0.100 M = [KCN]? 4.7 7.0 9.3 d. 14.0 Answer: c

For HCN, Ka = 4. 9  10−10. [HCN] = 0. 100 M, [KCN] = 0 For HCN, Ka = 4.9  10−10. [HCN] = 0.100 M, [KCN] = 0.200 M, pH of buffer solution = _____. 7.0 9.0 9.3 d. 9.6 Answer: d

For HCN, Ka = 4. 9  10−10. [HCN] = 1. 00 M, [KCN] = 0 For HCN, Ka = 4.9  10−10. [HCN] = 1.00 M, [KCN] = 0.100 M, pH of buffer solution = _____. 7.0 8.3 9.0 d. 9.3 Answer: b

Ka = [H+][A−] Kw = [H+][OH−] = 10−14 pH = pKa + d. pKa = pH + Select the correct representation of the Henderson-Hasselbach equation? Ka = [H+][A−] Kw = [H+][OH−] = 10−14 pH = pKa + d. pKa = pH + Answer: c

When titrating a weak base with a strong acid, a good indicator to use would be methyl red (color change at pH = 5). b. bromothymol blue (change at pH = 7). c. phenolphthalein (change at pH = 9). d. None of the above Answer: a

When titrating a weak acid with a strong base, a good indicator to use would be a. methyl red (color change at pH = 5). bromothymol blue (change at pH = 7). phenolphthalein (change at pH = 9). d. None of the above Answer: c

For BaCO3, Ksp = 5.0  10−9. What is [Ba2+] in a saturated aqueous solution of BaCO3? 7.1  10−5 M 1.0  10−8 M 2.5  10−9 M d. 5.0  10−9 M Answer: a

For BaF2, Ksp = 1.7  10−6. What is [Ba2+] in a saturated aqueous solution of BaF2? 1.7  10−6 M 3.4  10−6 M 7.6  10−3 M d. 1.5  10−2 M Answer: c

[Ag+][SO42−] [Ag+]2[SO42−] [Ag+] [SO42−]2 d. (2[Ag+])2[SO42−] Select the correct Ksp expression for the dissolution of silver sulfate, Ag2SO4. [Ag+][SO42−] [Ag+]2[SO42−] [Ag+] [SO42−]2 d. (2[Ag+])2[SO42−] Answer: b

For BaF2, Ksp = 1.7  10−6. What is [F1−] in a saturated aqueous solution of BaF2? 1.7  10−6 M 5.7  10−5 M 7.6  10−3 M d. 1.5  10−2 M Answer: d

For BaF2, Ksp = 1.7  10−6. If KF is added to a saturated solution so that [F1−] = 0.10 M, what is [Ba2+]? 1.7  10−6 M 1.7  10−5 M 1.7  10−4 M d. 1.7  10−3 M Answer: c

Ag(NH3)21+ Ag(NH3)2+ NH3Br1− d. NH4Br Silver bromide is insoluble in water, but dissolves in aqueous ammonia, due to the formation of _______. Ag(NH3)21+ Ag(NH3)2+ NH3Br1− d. NH4Br Answer: a

Which ion will precipitate first when sulfide ion is added to a solution containing all of the ions below? Hg2+ Pb2+ Zn2+ d. Cd2+ Answer: a

Which ion will precipitate when HCl is added to a solution containing all of the ions below? Zn2+ Pb2+ Al3+ d. Ba2+ Answer: b

Which ion will precipitate when phosphate ion is added to a solution containing all of the ions below? K1+ Ba2+ Na1+ d. NH41+ Answer: b

Which ion will form a precipitate upon addition of chloride ion, hydrogen sulfide, ammonium sulfide, or ammonium hydrogen phosphate? Ba1+ Na2+ K1+ d. NH41+ Answer: a