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| Understanding the concepts
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Check your answers |
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| 1.
| Define an acid and a base using the Brondsted-Lowry definition. What is the relationship between a conjugate acid-base pair?
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| 2.a.
| When an acid reacts with water, what are the products? Is water acting as a base or as an acid in this reaction? How does a strong acid differ from a weak acid? How does the strength of the conjugate base of a strong acid compare to the conjugate base of a weak acid? To answer these questions on acid and conjugate base strength, review the Ways to Describe Acid Strength Table on the Web site.
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| b.
| Consider 10 molecules of a strong acid and 10 molecules of a weak acid. Sketch what each solution would look like at equilibrium (ignore the water molecules). Check your answer by reviewing Figure 15.1 in the text. For a more advanced look at the differences between strong and weak acids, reference the Weak and Strong Acids Understanding Concepts on the CD. For the Exercises, ignore the Ka question. For the pH question, the solution with the higher pH will be the weaker acid (the acid with the fewest molecules dissociated). |
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| 3.a.
| . Play the Self-Ionization of Water to Form H+ and OH- in Equilibrium Visualization on the CD. The ion product constant, Kw, refers to a specific reaction. What is the Kw reaction? H+ is commonly used as an abbreviation for what substance? What is the value of Kw at 25°C? Using the value of Kw at 25C and the Kw expression, why does [H+] = [OH-] = 1.0 X 10-7 M in water when neither an acid nor a base is present? |
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| b.
| How are [H+] and [OH-] related in an acidic solution? In a basic solution?
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| 4.a.
| What are pH and pOH? Are pH and [H+] directly or inversely related? For a neutral solution of water, how are pH and pOH related at 25°C? |
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| b.
| When some acid is dissolved in water, how is pH related to pOH? How does the pH of a 0.10 M strong acid solution compare to the pH of a 0.10 M weak acid solution? When some base is added to water, how is pOH related to pH? For practice with pH calculations, do Problem 15.48 from the text.
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| c.
| Why is calculating the pH of a strong acid solution is much easier than calculating the pH of a weak acid solution? For practice calculating the pH of strong acid solutions, do problem 15.58 in the text.
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| 5.
| What is a buffered solution? What two compounds are present in a buffered solution? How does a buffer resist pH change? To answer these questions, open the Buffers Understanding Concepts on the CD and read the Introduction. Review Table 15.3 in the text for a good summary of buffer characteristics.
The Buffering Visualization on the CD shows an experiment of how a buffer resists pH change as HCl or NaOH is added. Note: The Animation part of the Buffers Exploration goes into more detail than discussed in the text. Also note that the Neutralization of a Strong Acid by a Strong Base Visualization on the CD provides a good pictorial view of titrations. If you discuss titrations in your class, check out this animation.
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| 6.
| Open Key Words on the CD and test your ability to define important terms presented in Chapter 15.
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| 7.
| Test your understanding of Chapter 15 by taking the ACE quizzes on the Web site.
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