LARN 158 C40D2

LARN 158 C40D2

Start the following in class:

1.  Write your journal entry on sheets of three holed 8.5 inch by 11 inch ruled paper in your Journal notebook. In the upper right corner white space of each upward facing page, write your hand in number within a circle followed by your name. Each journal entry should either be at least a paragraph of exemplary writing and penmanship concerning a single topic, or be a concept map relating chemistry terms. Begin each day’s paragraph with a topic sentence, follow with explained instances, and close with a focused summary statement.  Rather than just to find answers to questions, the goal of journaling is to reflect on, synthesize, and clearly express your thoughts in statements of your own understanding, so do not paraphrase material from other sources that you do not understand.

a. FYI: Another name for ethanoic acid is acetic acid and another name for ethanoate ion is acetate ion.

The required focus topics, J158A,  for today are

a. When is an aqueous solution of a salt acidic?

b. When is an aqueous solution of a salt basic?  Buffers are either solutions of a weak acid and its conjugate base found in one of its salts or solutions of a weak base and its conjugate acid found in one of its salts.

c. Describe what typically happens when a small amount of aqueous base is added to the protonated species in a buffer.  Specifically, what happens when an acid species were added to a buffer composed of equal volumes of 0.100 M ethanoic acid, CH₃COOH_(aq), mixed with 0.100 M sodium ethanoate Na⁺CH₃COO^–_(aq)?

d. Describe what typically happens when a small amount of  aqueous acid is added to the deprotonated species in a buffer.  Specifically, what happens when an acid species were added to a buffer composed of equal volumes of 0.100 M ethanoic acid, CH₃COOH_(aq), mixed with 0.100 M sodium ethanoate, Na⁺CH₃COO^–_(aq)?

1.b. The second required learning journal assignment for today, J158B, is as follows.

a. Why is it that when a strong acid neutralizes a strong base the equivalence point is near a pH of 7?  Please make your response longer than one sentence.

b. Why is it that when a strong acid neutralizes a weak base the equivalence point is near a pH of 5?  Please make your response longer than one sentence.

c. Why is it that when a weak acid neutralizes a strong base the equivalence point is near a pH of 9?  Please make your response longer than one sentence.

d. When doing a titration, why is it that the acid-base indicator selected for the titration sometimes has its end point color at a pH other than 7?  Please make your response longer than one sentence.

2.a. Use the PQ5R or SQ5R method to prepare study guide for text section 19.5 on Salts in Solution or go to https://socratic.org/chemistry to research the topics brought up in section 19.5 of your text.  Read section 19.5 in your chemistry text, pages 618 through 624, and as you do, create a study guide using the SQ5R or PQ5R method   explained in class and on the distributed handout packet.  You may record vocabulary entries in the body of your study guide, or you may check them off on the chapter 19 vocabulary list that was distributed as you think about the meanings of the terms and  add any notations to the vocabulary list for clarifications sake.

2.b.  After you have finished reading the assigned section of the chapter, answer the formative assessment questions and do some formative assessment problems to inform you about the degree of your comprehension and understanding.  Assessment questions are printed at the end of the section that you have just read.  Reflect on your answers to assure yourself that you have understood the major points in the section that you have just read.  Record your responses to questions that are challenging you, so that you can later review what you are learning.  If all problems seem easy to you, record the response to the problem that was least easy for you to answer.

Writing in blue or black ink, place your hand in number in a circle followed by your name in the upper right white space of a piece of three holed composition paper that hasn’t been written on.  Place the page reference for the problems to be considered to the left of the red marginal line on the first blue line.  Centered on the first blue line, write a descriptive title for the learning activity such as Section C1.4 Responses where C1.4 represents Chapter1.section4.  Before you write your response to each question or problem listed below, write its designation to the left of the red marginal line as listed below, followed by your response in ink to the right of the marginal line.

If solving the problem entails the use of multiplication or division, show your work by including a ? followed by the unit of the quantity you are solving for, an = sign, followed by the quantity given that has all or part of the dimensions of whatever quantity you are solving for, followed by mathematical operations on all labeled quantities, conversion ratios or comparison ratios that are used to obtain the sought for quantity.

• Study Conceptual Problem 19.2 on page 622 which reviews howto use equations to represent what happens when either some acid or some base is added to a buffer mixture.
• For practice problems I19-38 (In chapter 19, problem 38), and I19-39 on page 622 write down the specific acid-base equation being referred to and show your work.
• In the Section Assessment 19.5 on page 622, read, analyze, describe and explain practice problems I19-40ab (In chapter 19, problem 40ab), and I19-41.
• Then do problems I19-42abcd and I19-43ab. For practice problem sequence I19-42abcd, show the correctly  written formula, phase, and coefficient for each reactant and product of hydrolysis, and show the check for mass and charge balance for each expression.
• For practice problem sequence I19-43ab, show the correctly written formula, phase, and coefficient for each reactant and product of the acid-base reaction, and show the check for mass and charge balance for each expression.

After you have finished responding to the formative assessment questions and problems, check page R99 of the text and check each of those problems that you can by writing in either a check mark (√) or a correction in green ink.  Write down any question that you still have so that you can ask about it in class.  In the margin of your notebook page, circle the number of formative assessment questions do not have a suggested response given and check your response with that of your classmates when you come to class.

Recommended for those who have time left in their 45 minute study period, but not required of all:

1. Check out the student made Quizlet for chapter 19 at https://quizlet.com/210328966/ch-19-acids-bases-flash-cards/.  Do all the definitions reflect a thorough and correct understanding?
2. How do the properties of covalent molecular substances with hydrogen bonding typically differ from those covalent molecular substances that form molecules whose van der Waals attractive forces only weakly attract other molecules?
3. Think about the sixteen properties of covalent molecular substances listed on the Properties to be understood worksheet describing differences in the properties of metals, ionic compounds, covalent network solids, and covalent molecular compounds.  Continue to study this handout for understanding and review how the typical properties of members of these classes of compounds depend on whether the compound has localized or delocalized electrons, and upon whether strong metallic, ionic, or covalent bonding or weak van der Waals forces of attraction are predominant between representative particles of the substances.  Try to understand how each property of a given covalent molecular substance is related to the groups of covalently bonded atoms that form molecules whose van der Waals attractive forces only weakly attract other molecules.