ISM_chapter16_part1 - Chapter 16: Acids and Bases 721...

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Chapter 16: Acids and Bases 721 Chapter 16: Acids and Bases Teaching for Conceptual Understanding Instead of repeating the basic concepts of acids and bases that were introduced in Chapter 5, have students review that material on their own or assess their prior knowledge and retention with a worksheet or quiz. It is important that basic misconceptions are identified and corrected before getting into the more quantitative aspects of acid-base strength and pH. Chapter 16 is very important because the concepts of acids and bases apply to all science, engineering and pre- professional health career majors as well as many real-world experiences. Help students learn the material in depth. Once again use all three levels of understanding, macroscopic, particulate, and symbolic when explaining the material. Research has shown that students know the definitions of strong and weak acids and bases but are unable to translate those definitions into a particulate level understanding. Question 111 in Questions for Review and Thought addresses this issue, but you should remind the students that water is also present in those diagrams. Students have an innate sense of acid (or base) strength. If you ask them could a 4% solution of hydrochloric acid be substituted for vinegar (a 4% acetic acid solution) in a salad dressing, the majority will respond no. They know the hydrochloric acid is different from the acetic acid – that it is a harsher or more dangerous acid – but they do not know why. Suggestions for Effective Learning The concept of conjugate acid-base pairs is confusing for some students because they make the concept more difficult than it is. Clearly state that the formula (or structure) of the acid is the same as the base except that it has an additional hydrogen ion – that means it has both one more H atom and one more positive (or one less negative) charge. Table 16.2 and Figure 16.1 show the acid-base pairs. A good way to help students understand this concept is to give them incorrect pairs and ask them to explain why the pair is not a conjugate acid-base pair. Questions 4, 23, 24, and 112 in the Questions for Review and Thought get at this idea. The students might be confused by the various subscripts on the equilibrium constants, e.g., K w , K a , and K b . Explain that you are building on the basic ideas of equilibrium and these subscripts simply designate specific chemical reactions. Understanding and being able to use Table 16.2 (Ionization Constants for Some Acids and Their Conjugate Bases) is paramount to understanding and predicting chemical reactivity of acids and bases. Take the time to discuss this table in detail and provide students with sufficient practice in gleaning information from it. Cooperative Learning Activities
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This note was uploaded on 04/20/2008 for the course CHE 131 taught by Professor Kerber during the Spring '08 term at SUNY Stony Brook.

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ISM_chapter16_part1 - Chapter 16: Acids and Bases 721...

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