Oxidation and Reduction Questions

 

 

Power Point Lesson Notes- double click on the lesson number.                                                     

 

 


                                                                                         Worksheets                             Quiz

 

1. Oxidation, Reduction, Agents, & Reactions.             WS 1                                      

2. Lab: The Strength of Oxidizing Agents.                     Lab Handout                     

3. Oxidation Numbers Spontaneous Reactions              WS 2                                      

4. Oxidation Numbers, Application to Reactions.          WS 3                                          1

5. Balancing Redox Half Reactions Acid/Base.              WS 4                                      

6. Balancing Redox Reactions in Acid/Base.                  WS 5                                       2

7. Standard Potentials Using Chart.                               WS 6                                       3

8. Electrochemical Cells.                                               WS 7                                            

9. Electrochemical Cells Lab.                                                     

10. Electrolytic Cells.                                                    WS 8                                       4

11. Electrolytic Cells Lab.                                                                      

12. Application of Electrolytic Cells.                             WS 9                                       5

13. Application of Electrochemical Cells: Bat & Cor.    WS 10                                     6

14. Breathalyzer and review.                                        WS # 11 Practice Test # 1                

15. Review                                                                  WS # 12 Practice Test # 2                         

16. Review                                                                       

17. Test.                                                                                                   

 

 

Text book                   Hebden           Read Unit V 

If you want an A in this class you need to do this!!

 

 

 

 

 

 

 

 

Redox Half Reactions and Reactions WS #1

 

Define each

 

1. Oxidation                - loss of electrons

2. Reduction               - gain of electrons

3. Oxidizing agent      - causes oxidation by undergoing reduction

4. Reducing agent       - causes reduction by undergoing oxidation

 

Write half reactions for each of the following atoms or ions. Label each as oxidation or reduction.

 

5.                                 Al        ----------->     Al3+      +        3e-                                    oxidation             

6.                                 S          +        2e-    --------->     S2-                             reduction

7.                                 2O2-    ---------->        O2    +      4e-                          oxidation

8.                                 Ba2+     +    2e-   ----------->  Ba                                 reduction

9.                                                    2N3-    ---------->         N2    +      6e-                                             oxidation

10.                                                    Br2      +        2e-    --------->     2Br-                                            reduction

11.                               P    +      3e-        ---------->        P3-                               reduction

12.                               Ca       ----------->     Ca2+      +        2e-                                   oxidation

13                                                Ga3+     +    3e-   ----------->  Ga                                reduction

14.                               S          +        2e-    --------->     S2-                                                reduction

15.                                                    H2             --------->         2H+     +    2e-                          oxidation

16.                                                  2H+     +    2e-   --------->    H2                                                           reduction

17.                                               2F-      ---------->         F2    +      2e-                                              oxidation             

18.                                                  P3-      ---------->         P    +      3e-                             oxidation

 

 

 

 

 

 

 

 

Balance each spontaneous redox equation. Identify the entities reduced and oxidized. State the reducing agent and the oxidizing agent.

 

19.   Al            &         Zn2+                           

 

                                        2Al      +                      3Zn2+                       2Al3+    +          3Zn

                        oxidized                      reduced

                        reducing agent           oxidizing agent

 

 

20.   F2                     &         O2-                               

                                                           

                                        2F2      +                      2O2-                         4F-       +          O2

                        reduced                       oxidized                     

                        oxidizing agent           reducing agent          

 

 

21.   O2            &         Ca                   

 

                        2Ca     +                      O2                                       2Ca2+   +          2O2-

                        oxidized                      reduced

                        reducing agent           oxidizing agent

 

 

22.  Al3+          &         Li                   

 

                        Al3+     +                      3Li                          Al                    +          3Li+    

                        reduced                       oxidized                     

                        oxidizing agent           reducing agent          

 

 

Label the species that is reduced, that is oxidized, the reducing agent and the oxidizing agent.

 

23.                   Fe2+                 +          Co                                       Co2+                 +          Fe

 

                        Co               Co2+    +  2e-   oxidation                                 Fe2+      +         2e-               Fe reduction

 

24.                   3 Ag+               +          Ni                                        Ni3+                 +          3 Ag

       

                        Ni                Ni3+     +  3e-               oxidation                     Ag+       +         1e-       Ag            reduction

 

25.                   Cu2+                            +          Pb                                        Pb2+                 +          Cu

 

                        Pb                Pb2+     +  2e-               oxidation                     Cu2+     +         2e-       Cu            reduction

 

26.                   O2                    +          2 Sn                                     O2-                   +          2 Sn2+

       

                        Sn                Sn2+     +  2e-                         oxidation                                                      O2            +    4e-         2O2-                  reduction

 

27.                   Co2+                 +          2 F-                                      Co                   +          F2

 

 

                        2F-              F2              +  2e-                         oxidation                                                      Co2+     +    2e-          Co            reduction

       

 

 

 

28. List the species (formulas from above) that lose electrons:

Co       Ni        Pb        Sn        F-

 

29. List the species (formulas from above) that gain electrons:

Fe2+        Ag+          Cu2+       O2            Co2+

 

 

For each of the following reactions, identify:

            -The Oxidizing Agent.

            -The Reducing Agent.

            -The Substance Oxidized.

            -The Substance Reduced.

 

30.       I-          +          Cl2       ---------->                    Cl-       +          I2

           

       

                        Substance oxidized     I-                                  Reducing agent           I-

                        Oxidizing agent          Cl2                               Substance reduced      Cl2

           

 

31.       Co       +          Fe3+                 ----------->                  Co2+     +          Fe2+

           

       

                        Substance oxidized     Co                   Reducing agent           Co

                        Oxidizing agent          Fe3+                 Substance reduced      Fe3+

 

 

32.       Cr6+     +          Fe2+                 ----------->                  Cr3+     +          Fe3+

           

       

                        Substance oxidized     Fe2+                 Reducing agent            Fe2+

                        Oxidizing agent          Cr6+                 Substance reduced      Cr6+

 

Redox Half Reactions and Reactions WS #2

 

1.   State the Oxidation Number of each of the elements that is underlined.

            a)  NH3                        -3                     b)  H2SO4                    6

            c)  ZnSO3                    4                      d)  Al(OH)3                 3

            e)  Na                          0                      f)  Cl2                          0

            g)  AgNO3                   5                      h)  ClO4-                      7

            i)  SO2                         4                      j)  K2Cr2O4                  3

            k)  Ca(ClO3)2              5                      l)  K2Cr2O7                  6

            m)  HPO32-                  3                      n)  HClO                     1

            o)  MnO2                     4                      p)  KClO3                    5

            q)  PbO2                      4                      r)  PbSO4                     2

            s)  K2SO4                    6                      t)  NH4+                       -3

            u)  Na2O2                    -1                     v)  FeO                        2

            w)  Fe2O3                    3                      x)  SiO44-                     -2

            y)  NaIO3                     5                      z)  ClO3-                      5

            aa)  NO3-                     5                      bb)  Cr(OH)4               4         

            cc)  CaH2                    -1                     dd) Pt(H20)5(0H)2+     +3

            ee)  Fe(H2O)63+           +3                    ff)  CH3COOH                        0

 

2.   What is the oxidation number of carbon in each of the following substances?

            a)  CO                         2                      b)  C                              0

            c)  CO2                        4                      d)  CO32-                      4

            e)  C2H6                       -3                     f)  CH3OH                   -2

 

3.   For each of the following reactions, identify: the oxidizing agent, the reducing agent, the substance oxidized and the substance reduced.

a)   Cu2+ (aq)     +          Zn (s)                -------->           Cu (s)    +          Zn2+ (aq)

                       

                        Substance oxidized                            Zn                    Substance reduced                       Cu2+   

                        Oxidizing agent                                  Cu2+                Reducing agent                             Zn       

 

b)   Cl2 (g)         +          2 Na (s) -------->           2 Na+ (aq)         +          2 Cl- (aq)

                       

                        Substance oxidized                 Na                   Substance reduced                  Cl2

                        Oxidizing agent                                  Cl2                   Reducing agent                                   Na      

 

 

4.         Circle each formula that is able to lose an electron

       

            O2                    Cl-                   Fe                                Na+

 

5.         Determine the oxidation number for the element underlined.

            PbSO4              +6                               ClO3-               +5

            HPO32-             +3                                Na2O2              -1

            CaH2               -1                                 Al2(SO4)3             +6

            NaIO3              +5                                C4H12               -3

 

6.         Al3+    +       Zn                        →        Al        +          Zn2+

           +3                  0                                     0                         +2       oxidation numbers!                  

           

            Substance oxidized    Zn           Oxidizing agent    Al3+

       

7.         Cr2O72-            +          ClO2-    →         Cr3+     +          ClO4-

              +6                               +3                  +3                    +7            oxidation numbers      

 

            Substance reduced    Cr2O72-           Oxidizing agent  Cr2O72-           

 

8.         State the Oxidation Number of each of the elements that is underlined.

       

            a) NH3             -3                                 b) H2SO4                     +6              

            c) ZnCO3             +4                                d) Al(OH)3                  +3           

            e) Na               0                                  f) Cl2                           0           

 

9.         Balance the redox equation using the half reaction method.

                        Al        &         AgNO3

 

                                    Al     →  Al3+    +   3e-

                        3(Ag+   +  1e-    →     Ag)

            Al        +          3Ag+   →     Al3+     +     3Ag

 

10.       Circle each formula that is able to lose an electron

                                   

            O2                                Cl-                   Fe                    Na+

 

11.       Cr3+       +        ClO4-                       →        Cr2O72- +          ClO2-  

           +3                      +7                                       +6                  +3            oxidation numbers      

            Substance reduced     ClO4-     Oxidizing agent         ClO4-

 

12.       O3   +    H2O   +  SO2  →    SO42-    +    O2     +   2H+

             ?                        +4            +6                0            oxidation numbers      

                 Substance oxidized                SO2     Reducing  agent      SO2

 

13.       3As2O3    +    4NO3-  +  7H2O   +  4 H+   →  6H3AsO4    +   4NO

              +3                 +5                                                  +5               +2            oxidation numbers      

                 Substance reduced     NO3-                            Reducing agent            As2O3

 

 

WS # 3            Spontaneous and Non-spontaneous Redox Reactions        

 

Describe each reaction as spontaneous or non-spontaneous.

 

1. Au+3     +      Fe+3     ----->    Fe+2          +     Au                  nonspontaneous (two oxidizing agents)

 

2. Pb     +         Fe+3      ------>    Fe+2          +     Pb+2             spontaneous

 

3. Cl2     +      F-           ------>    F2          +     2Cl-                  nonspontaneous

 

4. S2O8-2    +    Pb        ------>     2SO4-2     +    Pb+2              spontaneous                          

 

5.Cu+2    +    2Br-         ------>     Cu     +    Br2                       nonspontaneous                                

 

6. Sn+2     +    Br2        ------>     Sn+4    +    2Br-                    spontaneous

 

7. Pb+2     +    Fe+2       ------>     Fe+3    +    Pb                      nonspontaneous                                

 

8. Can you keep 1 M HCl in an iron container. If the answer is no, write a balanced equation for the reaction that would occur. No

 

                                    Fe        +          2H+      -------->           Fe2+     +          H2

 

 

9. Can you keep 1 M HCl in an Ag container. If the answer is no, write a balanced equation for the reaction that would occur.

 

 

Yes.  There is no reaction.

 

 

10. Can you keep 1 M HNO3 in an Ag container. If the answer is no, write a balanced equation for the reaction that would occur. (remember HNO3 consists of two ions H+ and NO3-)

 

 

No       3Ag     +          NO3-    +          4H+      -------->   3Ag+               +      NO      +     2H2O                                    

 

 

 

11. Can you keep 1 M HNO3 in an Au container. If the answer is no, write a balanced equation for the reaction that would occur. (Remember, HNO3 consists of two ions H+ and NO3-)

 

Yes.  There is no reaction.

 

12. Circle each formula that is able to lose an elecron

           

        O2                        Cl-                   Fe                                Na+

 

13. Determine the oxidation number for the element underlined.

        PbSO4                  6                                  ClO3-               5

        HP032-                  3                                  Na2O2              -1

        CaH2                    -1                                 Al2(SO4)3             6

        NaIO3                  5                                  C4H12              -3

 

 

14.     Al3+    +       Zn  --------->         Al        +          Zn2+

 

        Substance oxidized         Zn                    Oxidizing agent          Al3+

       

15.       Cr2O72-            +   ClO2-    ------------>         Cr3+     +          ClO4-

 

        Substance reduced          Cr2O72-           Oxidizing agent          Cr2O72-

 

 

 

16. State the Oxidation Number of each of the elements that is underlined.

       

        a) NH3                  -3                     b) H2SO4                     6         

        c) ZnCO3                  4                      d) Al(OH)3                  3

        e) Na                     0                      f) Cl2                           0

 

 

17. Balance the redox equation using the half reaction method.

                       

 

            Al                    +          3Ag+    ---------->        Al3+     +          3Ag

 

 

18. Circle each formula that is able to lose an electron

                                   

O2        Cl-                   Fe                    Na+

 

Determine the oxidation number for the element underlined.

19.       PbSO4                           2         

20.       ClO3-                            5         

21.       HPO32-                         3         

22.       Na202                           -1

23.       CaH2                           -1

24.       NaIO3                          5

25.       C4H12                          -3

26.       Al2(SO4)3                         6

 

27.       Al3+     +          Zn        ---------->        Al        +          Zn2+

 

                        Substance oxidized                 Zn                                Oxidizing agent                Al3+    

 

 

28.                   Cr2O72-            +          ClO2-   ---------------->           Cr3+       +        ClO4-

 

                        Substance reduced                  Cr2O72-                       Oxidizing agent                Cr2O72-

           

29.    O3   +    H2O   +  SO2  ----->    SO42-    +    O2     +   2H+

 

                 Substance oxidized                        SO2                             Reducing  agent      SO2

 

30.   3As2O3    +    4NO3-  +  7H2O   +  4 H+   -------->  6H3AsO4    +   4NO

 

                    Substance reduced          NO3-                            Reducing agent                       As2O3

 

 

 

 

WS # 4                        Balancing Redox Reactions

 

 

Balance each of the following half-cell reactions.  (In each case assume that the reaction takes place in an ACIDIC solution.)  Also, state whether the reaction is oxidation or reduction.

 

1.                     5H2O  +          S2O32-    --------------> 2SO42-                      +                10H+    +          8e-

           

                        oxidation

 

2.                     8H+      +          5e-       +          MnO4-   --------------> Mn2+    +          4H2O

           

                        reduction

 

3.                     4H2O  +          As     -------------->     AsO43-                     +                8H+         +          5e-

           

                        oxidation

 

4.                     7H2O  +          2Cr3+    ----------->       Cr2O72-                   +                14H+      +          6e-

           

            oxidation

 

5.                     2H2O  +          Pb2+        -------------->  PbO2     +                4H+         +          2e-

                                   

                  oxidation

 

6.                     8H+         +                SO42-   +          6e-       --------------> S                      +      4H2O

           

                        reduction

 

7.                     4H+         +          NO3-     +          3e-            ------------->    NO      +          2H2O

           

            reduction

 

8.                     10H+      +          8e-            +          NO3-    -------------->    NH4+      +          3H2O

           

                        reduction

 

9.                     12H+      +          10e-         +          2BrO3-    -------------->            Br2           +      6H2O

           

                        reduction

 

Balancing Half Cell Reactions

 

Balance in basic solution.

 

10.       3e-       +          2H2O    +        NO3-      -------------->  NO      +         4OH-

 

 

11.       4H2O  +          5e-       +          MnO4-                      --------------> Mn2+      +          8OH-

           

 

12.       2H2O         +    2IVO3  +        8e-  -------------->      I2               +          2VO22-    +    4OH-

           

 

13.          2IVO3    +      2e-  -------------->      I2               +          2VO3-   

           

 

14.       Pb2+    +   4OH-     -------------->     PbO2    +   2H2O   +   2e-

           

 

15.       4H2O  +          6e-       +          SO42-    --------------> S                       +          8OH-

           

 

16.       10 OH-      +                S2O32-    --------------> 2SO42-  +          5H2O  +          8e-

           

 

 

17.       7H2O  +          8e-       +          NO3-      -------------->  NH4+      +          10 OH-

           

 

 

18.       6H2O  +          10e-     +          2BrO3-    -------------->  Br2        +          12 OH-

                       

 

 

19.  Determine if each of the following changes is oxidation, reduction or neither.

                       

                        SO32-               -------->           SO42-                           oxidation

                        CaO                 -------->           Ca                                reduction       

                        CrO42-              -------->           Cr2O72-                        neither

                        CrO42-              -------->           Cr3+                             reduction

                        2I-                    -------->           I2                                 oxidation

                        IO3-                  -------->           I2                                 reduction

                        MnO4-             -------->           Mn2+                            reduction

                        ClO2-               -------->           ClO-                             reduction

 

 

20.       Cr2O72-                                +          Fe2+     -------->           Cr3+     +          Fe3+

           

            Substance oxidized                 Fe2+                                         Substance reduced            Cr2O72-

            Oxidizing agent                      Cr2O72-                                           Reducing agent                 Fe2+    

 

 

 

WS #5    Balancing Redox Reactions in Acid and Basic Solution

 

 

Balance each redox equation.  Assume all are spontaneous.  Use the half reaction method.

 

1.         2O2-     +          2F2           ----------->      O2       +          4F-

     

2.         4Al      +          3O2         ----------->      6O2-     +          4Al3+

     

3.         2K       +          Zn+2        ----------->      Zn        +          2K+

 

 

Balance each half reaction in basic solution.

 

4.                     Cr2O72-                   +          7H2O  +          6e-            -------------->  14OH-      +       2Cr3+   

     

5.                     NO     +         4OH-               ------------------>              2H2O    +        NO3-  + 3e-      

     

6.                     2H2O    +        2e-       +          SO42-                         -------------->                   SO2         +      4OH-

     

7.                     2MnO2                    +          H2O       +          2e-       -------------->                   Mn2O3                     +      2OH-

 

 

Balance each redox reaction in acid solution using the half reaction method.

     

8.         8H+         +          3H2O2 +          Cr2O72-                   ------->            3O2     +          2Cr3+     +      7H2O

     

9.         TeO32 -  +  2N2O4             +    H2O    ------->      Te       +          4NO3-   +          2H+

     

10.      12H2O +          10V              ------->        6H+       +     3H2V2O42-   +          4VH3       

     

11.       8H+         +          5PbO2  +          I2         ------->            5Pb2+   +          2IO3-     +      4H2O

     

12.       12H2O +  8As             ------->            3H2AsO4-        +          5AsH3             +      3H+

 

 

Balance each redox reaction in basic solution using the half reaction method.

     

 

13.       3O2     +      8OH-       +   2Cr3+                ------->   H2O      +     3H2O2      +       Cr2O72-                 

     

14.       H2O      +   Te +          4NO3-   ------->            TeO32- +      2OH-       +          2N2O4                   

     

15.       10IVO3     +      28OH-            ------->   10VO22-   +  I2         +   8IO3-          14H2O

     

16.       8OH-   +           5Pb2+   +          2IO3-     ------->  5PbO2   +    I2   +   4H2O     

     

17.       2H2O      +  O2  +    4Fe(H2O)62+            ------->  4Fe(H2O)63+    +      4OH                          

 

 

 

State of the change represents oxidation, reduction or neither (use oxidation #s).

     

18.       MnO2              -------->                Mn2O3                                                                   reduction

19.       NH3                 -------->                           NO2                                                                 oxidation

20.       HClO4                      ------->                 HCl     +          H2O                                           reduction

21.       O2                    -------->                O2-                                                                         reduction

22.       P2O5                -------->                P4H10                                                                                      reduction         

 

Determine the oxidation number

23.       H2SO4             6                                              22.       HSO4-              6

24.       P4                                0                                              23.       NaH                -1

25.       UO3                           6                                                     24.       Na2O2             -1

 

26.       U2O5               5                                              25.       PbSO4           2

 

WS #6    Review

 

1.   Describe each in your own words

 

1. Oxidation                - loss of electrons

2. Reduction               - gain of electrons

3. Oxidizing agent      - causes oxidation by undergoing reduction

4. Reducing agent       - causes reduction by undergoing oxidation

 

 

 

2.   Write half reactions for each.  Describe as oxidation or reduction.  Circle all oxidizing agents.

     

      a)                           Na       ----------->     Na+      +        e-                                        oxidation

      b)                           Ca       ----------->     Ca2+      +        2e-                                   oxidation

      c)                           Al3+         +    3e-   ----------->  Al                                       reduction

      d)                           2F1-         ---------->     F2    +      2e-                                        oxidation

      e)                           N2             +      6e-    ---------->   2N3-                                       reduction

      f)                           2O2-        ---------->   O2    +      4e-                                          oxidation             

 

3.   Write the reaction between the following:  Use the half reaction method.

     

a)  Ca  +          Al(NO3)3

 

        3Ca          +          2Al3+     ------------->  2Al       +          3Ca2+

                       

b)  Sn  +          AgNO3

     

      Sn  +          2Ag+     ------------->  2Ag      +          Sn2+

 

c)  Sn   +          Au(NO3)3

 

      3Sn     +     2Au3+     -------------> 2Au      +          3Sn2+

 

4.   Circle each reducing agent:         Cu       Cu+     Al        Al3+

 

5.   Circle each oxidizing agent:        F-         F          O2-       O2

 

6. Ni+2 reacts with Mn, however, Al+3 does not react with Mn. Rank the oxidizing agents in order of decreasing strength. Rank the reducing agents in order of decreasing strength.

 

strongest oxidizing agent      Ni2+     +          2e-       ----------->      Ni

                                                Mn2+    +          2e-       ----------->      Mn

                                                Al3+     +          3e-       ----------->      Al        strongest reducing agent

 

 

7. Ag+ reacts with Pb, however, Ca+2 does not react with Pb. Rank the reducing agents in order of decreasing strength. Rank the oxidizing agents in order of decreasing strength.

 

strongest oxidizing agent      Ag+      +          1e-       ----------->      Ag

                                                Pb2+     +          2e-       ----------->      Pb

                                                Ca2+    +          2e-       ----------->      Ca       strongest reducing agent

 

8. Cl2 reacts with Ag, however, Ag does not react with Mg+2. Rank the oxidizing agents in order of decreasing strength. Rank the reducing agents in order of decreasing strength.

 

strongest oxidizing agent      Cl2       +          2e-            -------->           2Cl-    

                                                Ag+      +          1e-       ----------->         Ag

                                                Mg2+    +          2e-       ----------->        Mg      strongest reducing agent

 

9. Ni+2 reacts with Mn, however, Al+3 does not react with Mn. Rank the reducing agents in order of decreasing strength. Rank the oxidizing agents in order of decreasing strength.

 

strongest oxidizing agent      Ni2+     +          2e-       ----------->       Ni

                                                Mn2+    +          2e-       ----------->      Mn

                                                Al3+     +          3e-       ----------->      Al        strongest reducing agent

 

10. Cl2 reacts with Br-, however, I2 does not react with Br-. Rank the oxidizing agents in order of decreasing strength. Rank the reducing agents in order of decreasing strength.

 

strongest oxidizing agent      Cl2       +          2e-            -------->           2Cl-    

                                                Br2      +          2e-            -------->           2Br-

                                                I2         +          2e-            -------->           2I-        strongest reducing agent

 

 

Classify as oxidation, reduction or neither.  

 

11. SO42-         -------->           S2-                                 reduction

12. MnO2        -------->           MnO4-                          oxidation

13. Cr2O72-      -------->           CrO42-                       neither

14. IO3-                        -------->           I2                  reduction

 

15. Given the following lab data

 

            SnCl2               &         Ni                    Spontaneous

            Ni(NO3)2         &         Fe                    Spontaneous

            Cr(NO3)3         &         Fe                    Non spontaneous.

 

i) Write three balanced equations.

            Ni        +          Sn2+     ------------->    Ni2+      +          Sn

            Fe        +          Ni2+     ------------->    Fe2+     +          Ni

            Fe        +          Cr3+     <-------------   Fe2+     +          Cr

 

ii) Rank the oxidizing agents in decreasing order of strength.

     

strongest oxidizing agent      Sn2+     +          2e-       ----------->      Sn

                                                Ni2+     +          2e-       ----------->      Ni

                                                Fe2+     +          2e-       ----------->      Fe

                                                Cr3+     +          3e-       ----------->      Cr        strongest reducing agent

 

 

iii) Rank the reducing agents in decreasing order of strength.  See above.

           

iv) Will SnCl2 react with Cr? Explain?  Yes, because Sn2+ is a stronger oxidizing agent than Cr3+ .

           

v) Will Fe2+ react with Sn?                No, because Fe2+ is a weaker oxidizing agent than Sn2+

 

16.                  2H+      +          2MnO4-           +          5H2S   -------->           5S        +   6H2O   +    2MnO

                                                oxidizing agent           reducing agent

     

 

17.       2H+   +   10SO42-         +          4Br2    ---------->   5S2O32-   +   8BrO3-   +   H2O  

                        oxidizing agent        reducing agent

 

 

 

18.      Balance the redox equation in acid solution    IPO4  →   I2   +    IO3-    +    PO43-

         

           Hint: You need two half reaction

 

                 IPO4   →   I2                 +        PO43-

 

 

          IPO4   →  IO3-     +      PO43-

 

                       

          9H2O   +   5IPO4    →    3IO3-    +    I2   +    5PO43-    +   18H+

 

 

19.     Describe as spontaneous or non-spontaneous.  Use your reduction potential chart.

           

            a)         ZnCl2  &         Cu                        nonspontaneous        

            b)         CuCl2  &         NaCl                   nonspontaneous

            c)         Br2       &         Fe2+                   spontaneous

            d)         H2S      &         Al3+                        nonspontaneous

 

20.                   Can you keep HCl in a Zn container?                        No, Spontaneous reaction.

 

                        What about an Au container?                         Yes, nonspontaneous reaction.

 

Balance in basic solution

 

 

21.                               H2O   +    10SO42- +  4Br2    ------> 5S2O32-  +    2OH-    +    8BrO3-

 

 

 

 

Classify as an oxidizing agent, reducing agent or both based on its position on the table.

State the Eoor voltage of its position. Some of these are both, so state two voltages and indicate that it can be an oxidizing and reducing agent.

 

e.g.                  MnO4-  (in acid)                                  oxidizing agent                             1.51 v

            22.       Br2                                               oxidizing agent                                       1.09 v

            23.       Fe2+                                         oxidizing agent / reducing agent            -0.45 v / - 0.77 v

            24.       MnO4-  (water)                                    oxidizing agent                             0.60 v

            25.       Ni                                            reducing agent                                         0.26 v

            26.       Cr3+                                         oxidizing agent                                       -0.74 v / -0.41v

            27.       H2O                                         oxidizing agent / reducing agent           -0.41 v / -0.82 v

 

Indicate as spontaneous or non-spontaneous.

            28.       MnO4-             &         Fe2+                             non-spontaneous

            29.       Cu2+                 &         Br-                                non-spontaneous

            30.       HNO3              &         Ag                   spontaneous

            31.       MnO4- (acid)   &         H2O                 spontaneous

            32.       Ni(s)                 &         Al3+                             non-spontaneous

            33.       HCl                 &         Mg                  spontaneous

 

Write each oxidation and reduction half reaction for each question above. Determine the Eo for each. Calculate the Eo for the overall reaction.

 

34.                   MnO4-     +      2H2O     +   3e-   -------->       MnO2      +      4OH-               +0.60 v

                                    3(Fe2+    ----------->    Fe3+      +     1e-)                                              -0.77 v

MnO4-     +      2H2O     +   3Fe2+    -----------> 3Fe3+     +  MnO2        +      4OH-                         -0.17 v

 

35.

 

 

36.       NO3-    +          4H+      +3e-     ----------->      NO      +          2H2O                          +0.96 v

                                    3(Ag ----------> Ag+   +          1e-)                                                      -0.80 v

            NO3-    +          4H+      +     3Ag ----------> NO          +          2H2O   +   3Ag+            +0.16 v

 

37.

 

 

38.

 

 

39.                               2H+      +          2e-       ------> H2                                                        0.00 v

                                    Mg      ---------->        Mg2+    +      2e-                                               2.37 v

Mg      +          2H+      ---------->        Mg2+    +      H2                                   2.37 v

 

 

 

WS # 7            Electrochemical Cells

 

1. Oxidation is when electrons are lost.

 

2. Reduction is when electrons are gained.

 

3. The reducing agent undergoes oxidation.

 

4. The oxidizing agent undergoes reduction.

 

5. A negative voltage means the reaction is nonspontaneous.

 

6. In an electrochemical cell electrons exit the electrode, which is negative.

 

7. In an electrochemical cell the reduction reaction is higher on the chart, while the

oxidation reaction is lower.                          .

 

8. The cathode is the site of reduction and the anode is the site of oxidation.                         .

 

9. Anions migrate to the anode and cations migrate to the cathode.

 

10. Anions have a negative charge and cations have a positive charge.

 

 

 

Draw and completely analyze each electrochemical cell.

 

11. Zn  / Zn(NO3)2         Cu / Cu(NO3)2

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

12. Ag  / AgNO3         H2 / HCl

 

 



 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

WS # 8

 

 

1. In an electrolytic cell, reduction occurs at the negative electrode and oxidation occurs at the positive electrode.

 

2. If there are two possible reduction reactions, the highest one on the chart occurs.

 

3. For reduction, the chart is read from left to right.

 

4. For oxidation, the chart is read from right to left and the sign of the voltage is changed.

 

5. If there are two possible oxidation reactions, the lowest one on the chart occurs.

 

6. Corrosion of a metal is oxidation.

 

7. Electrolysis uses electrical energy.

 

8. Electrochemical cells produce electrical energy.

 

9. Electrolytic cells use electrical energy.

 

10. What is the standard reference cell? hydrogen   Eo = O v

 

 

Draw and completely analyze each electrolytic cell.

11. Molten NaCl

 

 


 

 

 

 

 

 

 

 

 

 

 

 

Cathode:  Na+   +   1e-       Na(s)     -2.71 v                                                 Anode:  2Cl-      Cl2  +  2e-        -1.36 v

 

Overall:  2Na+   +  2Cl-      Cl2  +  2Na(s)   -4.07 v                                     MTV = +4.07 v

 

 

 

 

 

 

12. Aqueous Na2SO4

 


 

 

 

 

 

 

 

 

 

 

 

 

Cathode:  2H2O   +   2e-       H2   +  2OH-    -0.41 v                                  Anode:  H2O       2H+   +   1/2O2  +  2e-      -0.82 v

 

Overall:  H2O     H2 +   1/2O2       -1.23 v                                                 MTV = +1.23 v

 

 

 

13. Liquid K2O

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

Cathode:  K+   +   1e-       K(s)         -2.93 v                                                 Anode:  2O2-      O2  +  4e-            ? v

 

Overall:  4K+   +  2O2-      O2  +  4K(s)       -? v                  MTV = +? v

 

 

 

 

 

14. 1.0 M LiI

 


 

 

 

 

 

 

 

 

 

 

 

Cathode:  Cathode:  2H2O   +   2e-       H2   +  2OH-          -0.41 v          Anode:  2I-      I2  +  2e-          -0.54 v

 

Overall:  2H2O   +   2I-      I2  +   H2   +  2OH-      -0.95 v             MTV = +0.95 v

 

 

15. 250ml of 0.200M MnO4- reacts with excess SO3-2.  How many grams of MnO2 are produced? This is Chemistry 11 stoichiometry.        2MnO4- + 3SO3-2 + H2O -----> 2MnO2 + 3SO4-2 + 2OH-

 

0.250L  MnO4-  x   0.200 mol   x   2 mol MnO2     x   86.9g  =  4.34g          

                                    L                2 mol MnO4-        mol

 

 

 

16. Determine the oxidation number for each underlined atom.

      MnO2        4          Cr2O7-2     6      IO3-      5          C2O4-2    3        Al(NO3)3         5

 

17.  Describe each term:

 

Salt bridge- a u-tube filled with salt solution that allows ions to flow in an electrochemical cell.

Electrolyte- a solution that conducts electricity                 

Anode- an electrode that is the site of oxidation

Cathode- an electrode that is the site of reduction 

Spontaneous- a reaction that occurs naturally and has a positive voltage

Electron affinity- the ability of a metal to attract electrons

 

18. What would happen if you used an aluminum spoon to stir a solution of FeSO4(aq) ? Write a reaction and calculate Eo.

 

2Al      +          3Fe2+   ------->            2Al3+   +          3Fe                  E0 = 1.21 v             Spontaneous. There would be a reaction!

 

 

19. Draw an electrochemical cell using Cu and Ag electrodes.

 

Cathode (+)                                                                Anode (-)

Ag                                                                               Cu

Ag+  + 1e--------->  Ag                        0.80v                           Cu   ------->  Cu2   +   2e        -0.34v

 

2Ag+    +    Cu   ------>     2Ag    +    Cu2+                  E0 = 0.46 v      spontaneous

 

 

 

20.  250ml of .500M MnO4- are required to titrate a 100ml sample of SO3-2.  Calculate the [SO3-2]

       2MnO4- + 3SO3-2 + H2O -----> 2MnO2 + 3SO4-2 + 2OH- 

 

.250L  MnO4-  x   0.500 mol   x   3 mol SO3-2           

                                    L              2MnO4-                  =          1.88M

                        0.100L

 

 

21. How is the breathalyzer reaction used to determine blood alcohol content (you might need to look this up in your textbook)?

 

The breathalyzer reaction uses a spontaneous redox reaction between acidic Cr2O72- and ethanol C2H5OH. If alcohol is present in your breath sample, it will react with a solution of Cr2O72- reducing the orange color as it reacts to form Cr3+, which is green. The drunker you are, the greater the reduction in orange color, which is measured with a spectrophotometer. 

 

 

22.     2H+ + Mg-----> Mg+2 +H2

            

Oxidizing agent                      H+                    Reducing agent                       Mg

 

 

 

 

WS #9             Electrolytic, Electrochemical Cells & Application

 

Determine the half reactions for each cell and the cell voltage or minimum theoretical voltage and overall equation.

 

1. Ag / Pb electrochemical cell.

 

Anode:                        Pb                                                                    Cathode:                    Ag 

Anode reaction:          Pb     -------->  Pb2+    +   2e-                          Cathode reaction:                Ag+      +   1e-    ------->  Ag                                     

Overall reaction:           Pb   +   2Ag+            ----->   Pb2+    +         2Ag          Voltage:   0.93v                

 

2. ZnCl2(l) electrolytic cell (electro-winning)

 

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          2Cl-  --------> Cl2   +   2e-             Cathode reaction:             Zn2+      +   2e-    ------->  Zn                                     

Overall reaction:           2Cl-     +   Zn2+         ----->   Cl2           +    Zn        MTV:   +2.12 v                 

 

3. CuSO4(aq) electrolytic cell (electro-winning)

 

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          H2O  --------> 2H+      +   1/2O2   +   2e-             Cathode reaction:                Cu2+      +   2e-    ------->  Cu                                     

Overall reaction:           H2O   +   Cu2+          ----->   2H+      +   1/2O2   +    Cu        MTV:   +0.48 v                 

 

 

4. The electrolysis of 1M NaI (electro-winning)

 

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          2I-  --------> I2   +   2e-                                    Cathode reaction:  2H2O  +  2e- ------->  H2 + 2OH-                                     

Overall reaction:           2H2O   +   2I-           ----->   H2   +   2OH-   +    I2        MTV:   +0.95 v                 

 

 

5. The reaction needed to make Al. The electrolyte is  Al2O3 and its phase is molten (molten or aqueous).

 

To lower the mp. from 2000 oC to 800 oC cryolite  is used.

 

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          2O2-   ------->  O2    +    4e-                            Cathode reaction:  Al3+      +   3e-    ------->  Al                                     

Overall reaction:           6O2-      +   4Al3+         ----->   3O2   +   4Al       

 

 

6.         The reaction needed to electroplate a copper penny with silver.

 

Anode:                        Ag                   Cathode:                      penny                                         

Anode reaction:            Ag-----> Ag+   +   e-                          Cathode reaction:        Ag+   +   e-   -----> Ag                              

 

 

7.         The reaction needed to nickel plate a copper penny.

 

Anode:                        Ni                   Cathode:                       penny                                         

Anode reaction:            Ni-----> Ni+2   +   2e-                        Cathode reaction:        Ni2+   +   2e-   -----> Ni                              

Possible Electrolyte      Ni(NO3)2               

 

8.         The reaction used in the electrorefining of lead.

 

Anode:                        Impure Lead                          Cathode:                     Pure Lead                                         

Anode reaction:            Pb-----> Pb+2   +   2e-           Cathode reaction:        Pb2+   +   2e-   -----> Pb                              

 

 

WS # 10  Electrolytic, Electrochemical Cells, Corrosion, & Cathodic Protection

 

Determine the half reactions for each cell and the cell voltage or minimum theoretical voltage.

 

1.         Zn / Mg  electrochemical cell

 

Anode:                        Mg                                                                  Cathode:                    Zn 

Anode reaction:          Mg     -------->  Mg2+    +   2e-                                    Cathode reaction:                Zn+2      +   2e-    ------->  Zn                                     

Overall reaction:           Mg   +   Zn2+ ----->   Mg2+    +         Zn          Voltage:   1.61v                

 

 

2.         The electrolytic cell used to produce Al.

 

Electrolyte:                Al2O3               Phase (aqueous or molten)          Molten          

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          2O2-   ------->  O2    +    4e-                            Cathode reaction:  Al3+      +   3e-    ------->  Al                                     

Overall reaction:           6O2-      +   4Al3+         ----->   3O2   +   4Al       

 

 

 

3.         The electrolysis KI(aq)

 

Anode:                        C                                                                                 Cathode:                    C 

Anode reaction:          2I-  --------> I2   +   2e-                                                Cathode reaction:  2H2O  +  2e- ------->  H2 + 2OH-                                     

Overall reaction:           2H2O   +   2I-           ----->   H2   +   2OH-   +    I2              MTV:   +0.95 v                 

 

4.         The electrorefining of Pb

 

Anode:                        Impure Lead                          Cathode:                     Pure Lead                                         

Anode reaction:            Pb-----> Pb+2   +   2e-           Cathode reaction:        Pb2+   +   2e-   -----> Pb                              

 

5.         Nickel plating an iron nail.

 

Anode:                        Ni                   Cathode:                       nail                                         

Anode reaction:            Ni-----> Ni+2   +   2e-                        Cathode reaction:        Ni2+   +   2e-   -----> Ni                               

Possible Electrolyte      Ni(NO3)2                The -ve side of the power supply is connected to the nail                     

 

6. Draw an Ag/ Zn electrochemical cell.

 

Anode:                        Zn                                                                    Cathode:                    Ag 

Anode reaction:          Zn     -------->  Zn2+    +   2e-                          Cathode reaction:                Ag+      +   1e-    ------->  Ag                                     

Overall reaction:           Zn   +   2Ag+            ----->   Zn2+    +         2Ag          Voltage:   1.56v                

 

 

7. Draw a KF(l) electrolytic cell.

 

Anode:                        C                                                                     Cathode:                    C 

Anode reaction:          2F-  --------> F2   +   2e-             Cathode reaction:                K+      +   e-    ------->  K                                     

Overall reaction:           2F-     +   2K+            ----->   Cl2           +    K        MTV:   +5.80v                 

 

 

8. Draw a KF(aq) electrolytic cell.

 

Anode:                        C                                                                                 Cathode:                    C 

Anode reaction:          H2O  --------> 2H+      +   1/2O2   +   2e-                    Cathode reaction:                2H2O  +  2e- ------->  H2 + 2OH-                                     

Overall reaction:           H2O              ----->   H2     +   1/2O2                                    MTV:   +1.23 v                 

 

 

9. Draw a FeI2(aq) electrolytic cell.

 

Anode:                        C                                                                                 Cathode:                    C 

Anode reaction:          2I-  --------> I2   +   2e-                                                Cathode reaction:  Fe2+  +  2e- ------->  Fe                                     

Overall reaction:           Fe2+     +   2I-             ----->   Fe        +    I2                           MTV:   +0.99 v                  

 

 

10. Draw a Cd/Pb electrochemical cell.  Cd is not on the reduction chart, however, the Cd electrode gains mass and the total cell potential is .5v.  Determine the half-cell potential for Cd.

 

 

Anode:                        Pb                                                                                Cathode:                    Cd 

Anode reaction:          Pb     -------->  Pb2+    +   2e-              0.13v              Cathode reaction:            Cd+2      +   2e-    ------->  Zn         x volts                           

Overall reaction:           Pb   +   Cd2+ ----->   Pb2+    +         Cd                     Voltage:   0.50v                

 

0.13 + x = 0.50            x = 0.37v

 

 

 

 

11. 2HIO3 + 5H2SO3 ----------> I2 + 5H2SO4 + H2O

    oxidizing agent                 HIO3                             substance oxidized           H2SO3                 

    substance reduced           HIO3                              reducing agent                H2SO3

 

 

12. What is the fuel in a fuel cell?     H2   and O2

 

13. Describe the differences and similarities between an electrolytic and electrochemical cell.

 

Electrolytic                                                                 Electrochemical

 

Uses electricity                                                          Produces electricity

Nonspontaneous                                                         Spontaneous

Makes chemicals                                                       Uses chemicals

Inert carbon electrodes                                             Usually has a salt bridge

The negative electrode is reduction                         The higher metal is reduction

 

Oxidation occurs at the anode and reduction occurs at the cathode.

Anions migrate to the anode and cations migrate to the cathode.

Electrons go from anode to cathode through the wire.

 

14. Describe and give two examples of electrowinning.       The electrolysis of water to make H2 and O2.        The electrolysis of Al2O3 to make Al and O2.

 

15. Describe and give one example of electrorefinning. The electrorefinning of Pb.

 

16. List three metals that can be won from aqueous solution.                      Pb        Au       Ag            Zn        Cu       Fe        Sn

 

17. List three metals that cannot be won from aqueous solution.     Na       K         Li        Ca            Mg      Al       

 

 

18. State two metals that can be used to cathodically protect Fe. Describe how they protect iron from corrosion.

 

Zn and Mg. When attached to Fe they form an electrochemical cell. Zn or Mg is a stronger reducing agent (lower on the chart) and is the anode and Fe is the cathode. Since the cathode is the site of reduction, Fe cannot oxidize or corrode.

 

19. Write the half reaction that describes the corrosion of iron. Fe -------->   Fe2+     +2e-

 

20. Write the half reaction that describes the reduction reaction that occurs when iron corrodes in air and water. 2e-  +   H2O  +  1/2O2  ---------->  2OH-

 

21. Why does iron corrode faster in salt water?        The salt acts like a salt-bridge and increases the rate of reaction in an electrochemical cell.

 

 

22. Write the anode and cathode reaction in an electrolytic cell with a CaCl2 (l) electrolyte.

 

Cathode:  Ca2+   +   2e-   ---------> Ca                      Anode:            2Cl-    ----------> Cl2     +    2e-  

 

23.  Explain why you would choose Zn or Cu to cathodically protect iron? Zn. It is a stronger reducing agent than Fe and it will allow Fe to be the cathode, which cannot corrode.

 

 

24. Choose a suitable redox reactant to oxidize Cl- to ClO4- in a redox titration.  

 

MnO4- in acid gives a spontaneous reaction as well as a color change from purple to clear.

 

25. Describe as an electrochemical or electrolytic cell:

           

a) Fuel cell                                          electrochemical          b)Charging a car battery            electrolytic

            c) Discharging a car battery               electrochemical          d) Ni plating                           electrolytic

            e) Industrial Al production                 electrolytic                 f) Cl2 production                     electrolytic

 

 

 

26) Al and AgNO3(aq) are mixed and the surface of the Al darkens. List the two oxidizing agents in decreasing strength.  List the two reducing agents in decreasing strength.

 

Oxidizing Agents       Ag+      Al3+

 

Reducing Agents        Al        Ag

 

29.       Analyze This

Label each anode and cathode. See Diagram
Write each anode and cathode reaction. See Diagram
Indicate the ion migration in each cell. See Diagram
Determine the initial cell voltage of the electrochemical cell. See Diagram
Determine the MTV for the electrolytic cell. See Diagram
Will electrolysis occur? Yes
Indicate electron flow. See Diagram
Indicate all electrodes that gain mass. Ag and Cu
Indicate all electrodes that lose mass. Mg
What happens to [NO3-] in the Mg half-cell? Decreases
What happens to the [Ag+] in the Ag half-cell? Decreases
What happens to [Mg2+] in the Mg half-cell? Increases
What is the equilibrium electrochemical cell potential? 0 V
What chemical is made at the Pt electrode on the right? Cu
What chemicals are made at the Pt electrode on the left? O2 and H+

Cell