by horse Comment Closed

LARN 167 C42D3

Start the following in class:

1.  For your journal today, J167A, you are to show how to use oxidation numbers and the single atom ratio method to balance four chemical expressions.  In your journal notebook, on the first blue line title this assignment Redox Problems.  a, b, c, and d. For each of problem,

  • record the oxidation number for each atom in each species on a short line segment drawn above the elements 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.
  • record the oxidizing agent, the reducing agent, and the atom ratio that could be used to balance the chemical expression.
  • Then balance the chemical expression. Use the single atom ratio method to balance the following expressions 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. 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.

a.       ___                 __ _ _                                __                    __  _ _

   __ Zn(s)  +  __ AgNO3(aq)  —–>   __ Ag(s)  +  __ Zn(NO3)2(aq)  

FYI: How to do problem a. 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 138 through 139 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

b.   This reaction occurs only in acidic media.

      __                 _ _ _                             _ _                    _ _                 _    _

__ S(s)  + __ HNO3(aq) —–> __ SO2(g)  + __ NO(g) + __ H2O(l) 

FYI: How to do problem b 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 140 through 141 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

c.  This reaction occurs only in acidic media.

       _ __   _                    _ _                            __ __                    __                  _  _             __ __

__ KMnO4(aq) +__ HCl(aq) —–> __ MnCl2(aq) +__ Cl2(g) +__ H2O(l) +__KCl(aq)  

FYI: How to do problem c 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 142 through 144 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

d.  This reaction occurs only in basic media.

       __                   _ _ _                           _ _                     _ __ _                      _   _

__ Br2(l) + __ KOH(aq) —–> __ KBr(aq) + __ KBrO3(aq) + __ H2O(l)

FYI: How to do problem 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 145 through 146 of the chapter 20 ActivInspire Oxidation-Reduction flipchart.

2.  Do all the pages in the chapter 20 [formative] Test A.  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.  Make sure you understand each word, idea, concept, or problem.

  • Show your oxidation number assignments and work either on scratch paper or on your formative test pages for Formative Test problems numbered 11, 12 ,13, 14, 17, 18, 19, 20, 23, 24, 26.
  • Show your oxidation number assignments and work in your formative test packet for Formative Test problems numbered 27a, 27b, 28, 29a, 29b, 29c, and 30:
  1. Neatly and completely write the chemical equation given in the problem and then draw a short line segment above each atoms element symbol in each given formula.
  2. On the short line segment drawn above the atoms elemental symbol in each reactant and product formula, write the oxidation number of each single atom after using the rules for assigning oxidation numbers to find the value for that particular atoms oxidation number.
  3. Also 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.
  4. Balance the chemical expression in problem 30 using the single atom ratio method 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. 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. Check out the student made Quizlet for chapter __ at https://quizlet.com/212581782/ch-20-oxidation-reduction-reactions-flash-cards/.  Do all the definitions reflect a thorough and correct understanding?
  2. Download current ActivInspire unit flipchartby logging on to the MNSD Google Drive and selecting it from the Student Resources > ActivInspire   Generally the flipchart name will begin with a capital U to designate the chemistry unit of study and end in a relatively high version number following the v at the end of the flipchart’s title.  Download this chapter’s flipchart after clicking on the following link for unit 15: Oxidation-Reduction.  Click through the chart quickly and take Cornell notes on concepts pertaining to the learning objectives that you are studying.  At the end of your study, write a summary statement of what you learned.
  3.  For today’s second journal entry in your journal notebook, J167B, 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 these fourteen terms:
    • oxidation,
    • reduction,
    • oxidizing agent,
    • reducing agent,
    • gain of electrons,
    • loss of electrons,
    • conservation of charge,
    • conservation of mass,
    • oxidation number,
    • ionic charge,
    • electronegativity,
    • uncombined element,
    • compound,
    • uncharged [zero net charge].

    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.