LARN 164 C41D4

LARN 164 C41D4

Your Goals:

Reading section 20.2 should give you an idea of how oxidation numbers are assigned and why they are assigned in the way that they are.  The journal questions bring out the meanings discussed in the reading selection.  The time focused on the reading and journaling is expected to be around 30 minutes.  The main concern for home learning activities is to develop understandings in your mind that you can then apply to solve problems.   Responding to the journal questions serves as a first step toward accomplishing that purpose.

With the understanding of why the priorities are as they are, the central focus of LARN 164 is to learn to apply the four rules and six priorities for assigning oxidation numbers introduced in LARN 163, with the ease that comes from practice.  Try spending no more than 10 minutes reviewing why the rules and priorities are as they are and follow up with applying those rules to the best of your ability in the time available on one or more of the problems listed.  Be patient and be ready to learn from your mistakes and struggles.

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.

1. The required focus activities, J164A, for today are

a.  Construct a table with three vertical columns and six horizontal rows and fill it out to compare the oxidation process to the reduction process that can occur simultaneously in a chemical reaction.  From left to right title the columns Aspect of Comparison, Oxidation, and Reduction.  In the first column under the Aspect of Comparison title, from top to bottom, list the points to be compared: Loss or Gain of Electrons, Shift of Electrons from or to an Atom in a Covalent Bond, Loss or Gain of Oxygen, Loss or Gain of Hydrogen, and Change in Oxidation Number.  [This chart is similar to but not identical to the one shown on p.635, Figure 20.1.]

Comparison of the Oxidation and Reduction Processes

Aspect of Comparison	Oxidation	Reduction
Loss or Gain of Electrons
Shift of Electrons from or to         an Atom in a Covalent Bond
Loss or Gain of Oxygen
Loss or Gain of Hydrogen
Change in Oxidation Number

b.  Learn the rules for assigning oxidation numbers given either in the document entitled  How to Assign Oxidation Numbers, or in the Introductory flipchart on Oxidation and Reduction , or if that is not handy, those given on page 639 of your text or in your learning packet handout.

c.  Copy the chemical equation and the net ionic equation given in Conceptual Problem 20.1 on page 634 into your learning journal.

• • Draw a short line segment above each atoms element symbol in each given formula in each equation.
  • On the short line segment drawn above the atoms elemental symbol in each reactant and product formula, use the rules for assigning oxidation numbers given on page 639 or in your chapter 20 informational packet to figure out and list the oxidation number of each single atom listed in both equations.
  • Notice that the oxidation numbers of the atoms composing a spectator ion do not change!

2. The required focus topics, J164B, for today are

1. According to the Merriam-Webster online dictionary an agent is something that produces or is capable of producing an effect.  How does the decrease in oxidation number in one of the atoms in the initial state of a redox reaction make the substance that contains it an oxidizing agent?
2. How does the increase in oxidation number in one of the atoms in the initial state of a redox reaction make the substance that contains it a reducing agent?

3.a.  Use the PQ5R or SQ5R method to prepare study guide for text section 20.2 on Oxidation Numbers or go to https://socratic.org/chemistry  to research the topics brought up in section 20.2 of your text.  Read section 20.2 in your chemistry text, pages 639 through 644, 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 20 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.

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.

• Refer to the document entitled  How to Assign Oxidation Numbers and notice how the unknown oxidation number of an atom for which there is no standard assignment rule exists (such as the S atom in BaSO₄) is determined by assigning the oxidation number to the other atom(s) for which there is a rule first, finding the subtotal(s) of charge for that/those atoms and writing it/them above the oxidation number(s) for that/those atom(s).  Then by using the idea that the total of all the subtotals of oxidation numbers will equal the total charge shown on the whole formula unit, the value of the unknown oxidation number for the atom can be determined by simple arithmetic.  Use the setup in the document entitled  How to Assign Oxidation Numbers .  As you did yesterday, on p. 634 do
• I20-1a again

  ___         ___               __  __           —- subtotal of charge

  ___         ___               __  __          —- oxidation number

2 Na_(s) +  S_(s)  —–>   Na₂S_(s) .

• I20-1b again

   ___       ___                        __  __         —- subtotal of charge

  ___       ___                         __  __        —- oxidation number

4 Al_(s) + 3O_2(g) —–>    2 Al₂O_3(s)

• In the Section Assessment 20.1 on page 638, read, analyze, describe and explain practice problems I20-7cdef and I20-8cdef using the same setup that you used for problems I20-7a and b, and I20-8a and b yesterday.  The setup is identical to that shown in the examples given in the Oxidation and Reduction flipchart that you should be examining.
• Study Conceptual Problem 20.2 on page 641 which shows how to assign oxidation numbers to single atoms according to the rules given in the oxidation-reduction flipchart, on page 639, or in your learning packet handout.
• Show your work including all oxidation number assignments for practice problems I20-9abcd (In chapter 20, problems 9a,b,c, and d) and I20-10abcd.
• Locate and turn to your worksheet and notes from a previous chapter on How does one use oxidation numbers to name ionic compounds?
• To show your work for I20-9abcd and I20-10abcd, use the same setup that we used before when we named the ionic compounds on that worksheet using the Stock system of nomenclature.
• Study Conceptual Problem 20.3 on page 643 which shows how to assign oxidation numbers to atoms according to the rules given in the oxidation-reduction flipchart, on page 639, or according to the rules given in class or in your learning packet handout.  Then use those oxidation numbers to determine which atoms are oxidized and which are reduced in a given oxidation-reduction (redox) process.  Finally, use a properly headed clean sheet of notebook paper to do problems I20-11a, I20-11b, I20-12a, and I20-12b given on page 643 of the text.
• For problem I20-11 be sure to skip two lines before copying each chemical equation onto the paper and then drawing a short line segment above each atoms element symbol in each given formula in each equation.  On the short line segment drawn above the atoms elemental symbol in each reactant and product formula, use the rules for assigning oxidation number given in the oxidation-reduction flipchart or on page 639 or in class to figure out and list the oxidation number of each single atom listed in each equation.
• For I20-11a and I20-11b use full sentences to explain which atoms are oxidized and which are reduced.
• For I20-12a and I20-12b use full sentences to identify the oxidizing agent and the reducing agent for each chemical reaction.
• In the Section Assessment 20.2 on page 643, read, analyze, describe and explain practice problems I20-13 (In chapter 20, problem 13), I20-14, I20-15ab, and I20-16ab.
• For problem I20-15ab use a setup similar to that used for Conceptual Problem I20-1a and b and identical to that given on the Introduction to Oxidation and Reduction flipchart to show  your work.

After you have finished responding to the formative assessment questions and problems, check page R100 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. Go back to our previous day’s learning journal entry that describes the process of elemental iron, Fe_(s), corroding in the presence of oxygen, O_2(g), and water, H₂O_(l), as a sequence of two oxidation-reduction reactions (LARN 163).

• • Draw a short line segment above each atoms element symbol in each given formula in each equation.
  • Refer to the rules for assigning oxidation numbers given on page 639 or in your learning packet handout.  On the short line segment drawn above the atoms elemental symbol, figure out and then list the oxidation number of each single atom involved in each corrosion reaction in the two balanced chemical expressions that you wrote.  The oxidation state of iron in each substance must be figured out using the insight that the total of all the oxidation numbers of all the atoms present in a substance is the charge shown to the upper right of the formula for that species in the chemical equation. [If no charge is shown to the upper right of the formula of the species written, the unshown charge is 0 (neutral).]

2. Download the Oxidation and Reduction flipchart from your MNSD Google Drive > Student Resources > ActivInspire Flipcharts folder or from the Infinite Campus web site.  Read and study the How to Assign Oxidation Numbers document.  Before going on to the next item in today’s home learning activity, review the four rules and six priorities for assigning oxidation numbers to single atoms of elements by heart.

3. 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?

4. 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.