LARN 166 C42D2

LARN 166 C42D2

Start the following in class:

1.  For the first part of today’s journal entry, J166A, assign oxidation numbers to each single atom of each chemical species in chemical expressions a and b given below and then show how those oxidation numbers can be used to balance the chemical expressions.  A page in your learning packet has space for you to show your work for these two problems, or you can do problems a and b in your journal notebook.

__ __                      __                             __ __                  __

a.  __ Fe₂O_3(s)     + __ C_(s)       →        __ CO_(g)     +  __  Fe_(s)

                     __ __                     __ __                    __ __                     __

b.  __ Fe₂O_3(s)     + __ CO_(g)     →     __ CO_2(g)    +   __  Fe_(s)

• Record the oxidation number for each atom in each species on a short line segment drawn above the element’s symbol in each formula given in the initial and final states of the chemical expression.
• Record the reduction half reaction and the oxidation half reaction for the transfer of equal numbers of electrons and the atom ratio that could be used to balance the chemical expression.
• Underneath each initial state species, label the oxidizing agent, the reducing agent.
• Then balance the chemical expression, showing all your work on the learning packet worksheet.  Use the single atom ratio method to balance the following expressions in neutral media as explained in the following notes.
  1. Correctly copy the formula and phase of each reactant and product in the unbalanced chemical expression onto the paper and then draw a short line segment above each atom’s element symbol in each given formula.
  2. Use the rules for assigning oxidation numbers to assign and record the oxidation number for a single atom of each element present in each substance or species on the short line segment drawn above the atom’s elemental symbol in each reactant and product formula, .
  3. If the expression to be balanced represents an oxidation-reduction (redox) process, write a reduction half reaction for a single atom of each substance being reduced and, underneath it,  write an oxidation half reaction for a single atom of each substance being oxidized.
  4. Multiply the half reactions by appropriate multipliers such that the total increase in oxidation number is equal to the total decrease in oxidation number, and then use the resulting ratio of the number of atoms that are reduced to the number of atoms that are oxidized simultaneously to select appropriate coefficients to balance those reduced and oxidized atoms in the chemical expression.
  5. Perform a mass balance (another T check) to check that the total number of each kind of atom is the same in the final state as in the initial state.

FYI: How to do problem 1.a. above is recorded step by step on one of the pages of the chapter 20 information packet distributed to you in class.

FYI: How to do problem 1.b. above is also recorded step by step on pages 173 through 175 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

For the second part of today’s journal entry, J166A, in your journal assign oxidation numbers to each single atom of each chemical species in chemical expressions c and d given below and then show how those oxidation numbers can be used to balance the following two chemical expressions.  Do the problem c and problem d in your journal notebook.

The following reaction only occurs in acidic solution.

c.          ____                     __ __                                                   ___                     ___

       __ Fe²⁺_(aq)   + __ MnO₄^– _(aq)  +                →       __ Fe³⁺_(aq) +  __ Mn²⁺ _(aq)    + 

• Record the oxidation number for each atom in each species on a short line segment drawn above the element’s symbol in each formula given in the initial and final states of the chemical expression.
• Record the reduction half reaction and the oxidation half reaction for the transfer of equal numbers of electrons and the atom ratio that could be used to balance the chemical expression.
• Underneath each initial state species, label the oxidizing agent, and the reducing agent.
• Then balance the chemical expression.  Use the single atom ratio method to balance the following expressions as explained in the following notes on how  to use the SINGLE ATOM RATIO method of balancing chemical expressions using oxidation numbers.

1. 1. Correctly copy the formula and phase of each reactant and product in the unbalanced chemical expression onto the paper and then draw a short line segment above each atom’s element symbol in each given formula.
   2. Use the rules for assigning oxidation numbers to assign and record the oxidation number for a single atom of each element present in each substance or species on the short line segment drawn above the atom’s elemental symbol in each reactant and product formula, .
   3. If the expression to be balanced represents an oxidation-reduction (redox) process, write a reduction half reaction for a single atom of each substance being reduced and, underneath it,  write an oxidation half reaction for a single atom of each substance being oxidized.
   4. Multiply the half reactions by appropriate multipliers such that the total increase in oxidation number is equal to the total decrease in oxidation number, and then use the resulting ratio of the number of atoms that are reduced to the number of atoms that are oxidized simultaneously to select appropriate coefficients to balance those reduced and oxidized atoms in the chemical expression.
   5. Compute and record the total charge of all the initial state species and compute and record the total charge of all of the final state species, that is, do a charge balance (T check).
   6. If the reaction occurs in acidic solution, add the necessary number of H⁺_(aq) ions to the side of the chemical expression that needs more positive charge to bring it into charge balance.
   7. If the reaction occurs in basic solution, add the necessary number of OH ^–_(aq) ions to the side of the chemical expression that needs more negative charge to bring it into charge balance.
   8. Perform a mass balance (another T check) to check that the total number of each kind of atom is the same in the final state as in the initial state.
   9. If the chemical process occurs in aqueous solution and the hydrogen and oxygen atoms are not in balance, bring the expression into mass balance by adding H₂O_(l) to the side of the expression that needs more hydrogen or oxygen atoms.

FYI: How to do problem 1.c. above is also recorded step by step on pages 120 through 127 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

d.       ___                  ___                                              __  __    __ __

     __ Fe_(s)     + __ O_2(g)                      →        __  Fe₂O₃ • FeO_(s)

FYI: How to do problem 1.d. above is also recorded step by step on one of the pages of the chapter 20 information packet distributed to you in class and is also recorded step by step on pages 128 through 130 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

2.  Do all the pages in the Section Review packet for chapter 20, Oxidation-Reduction Reactions. For each question or problem challenge, either answer the question to the best of your ability using one or more full sentences, or answer the problem to the best of your ability by recording any numbers and units together with the mathematical operations performed in symbolic terms, along with the solution to the problem which should be circled.

• As part of your review, record the oxidation number for each atom in each species on a short line segment drawn above the elements symbol given for Section 20.1 review problems numbered 10,  11, 20, Section 20.2 review problems numbered: 27a, 27b, 27c, 27d, and Section 20.3 review problems numbered: 21a, 21b, 22a, and 22b.
• Record the reduction half reaction and the oxidation half reaction for the transfer of equal numbers of electrons, and record the oxidizing agent, the reducing agent, and the atom ratio that could be used to balance the equation. 
• Balance all of the chemical expressions in Section 20.2 (problems 27a, 27b, 27c, 27d) and Section 20.3 (problems 21a, 21b, 22a, and 22b) using the single atom ratio method as explained in the following notes:

1. 1. Correctly copy the formula and phase of each reactant and product in the unbalanced chemical expression onto the paper and then draw a short line segment above each atom’s element symbol in each given formula.
   2. Use the rules for assigning oxidation numbers to assign and record the oxidation number for a single atom of each element present in each substance or species on the short line segment drawn above the atom’s elemental symbol in each reactant and product formula, .
   3. If the expression to be balanced represents an oxidation-reduction (redox) process, write a reduction half reaction for a single atom of each substance being reduced and, underneath it,  write an oxidation half reaction for a single atom of each substance being oxidized.
   4. Multiply the half reactions by appropriate multipliers such that the total increase in oxidation number is equal to the total decrease in oxidation number, and then use the resulting ratio of the number of atoms that are reduced to the number of atoms that are oxidized simultaneously to select appropriate coefficients to balance those reduced and oxidized atoms in the chemical expression.
   5. Compute and record the total charge of all the initial state species and compute and record the total charge of all of the final state species, that is, do a charge balance (T check).
   6. If the reaction occurs in acidic solution, add the necessary number of H⁺_(aq) ions to the side of the chemical expression that needs more positive charge to bring it into charge balance.
   7. If the reaction occurs in basic solution, add the necessary number of OH ^–_(aq) ions to the side of the chemical expression that needs more negative charge to bring it into charge balance.
   8. Perform a mass balance (another T check) to check that the total number of each kind of atom is the same in the final state as in the initial state.
   9. If the chemical process occurs in aqueous solution and the hydrogen and oxygen atoms are not in balance, bring the expression into mass balance by adding H₂O_(l) to the side of the expression that needs more hydrogen or oxygen atoms.

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

1.   For today’s second journal entry in your journal notebook,  J166B, you are to construct a concept map.  Please turn to page 656 in your text and, in your learning journal, construct a concept map relating the seven terms listed at the bottom of the page.  Copy the terms onto your page, draw ovals around each term, and connect the ovals  surrounding related terms with arrows.  Draw the arrows such that the  subject of each sentence explaining the relationship is at the tail of  the arrow, the verb describing the relationship of the subject to the  predicate is written beside the arrow, and the object or predicate  nominative of the verb that you have chosen is being touched by the  arrow head.
2. Review those concepts that we have discussed in class that are in your study guides, that are in your text study guide at the end of the chapter, and that on the chapter vocabulary sheet provided to you that describes what is  a substance, an element, a compound, a coarse mixture, a colloidal suspension, a solution;  an atom; a formula unit, a molecule; a phase, an aqueous phase;  a chemical change, a physical change; a chemical reaction, a reactant, a product, a word equation, and a formula unit equation.  How are these concepts different?  You need to be able to explain the meaning of each of these terms, and be able to differentiate the terms, be able to compare and contrast these related terms, and give examples that make clear the points that you are trying to explain.  Go over each of these concepts with your study partner.
3. Review the SI prefixes and their meanings until you can readily explain the meaning of each listed SI prefix as a numerical multiplier.