The anode used in the commercial production of Aluminum

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					CHAPTER 5 REVIEW

1.   The following represents the process used to produce iron from iron III oxide:
     Fe2O3 + 3CO → 2Fe + 3CO2 What is the reducing agent in this process?

     A.     Fe                                                C.      CO2
     B.     CO                                                D.      Fe2O3

2.   Consider the following reaction: 2HNO2 + 2I- + 2H+ → 2NO + I2 +2H2O
     The oxidation number for each nitrogen atom

     A.     increases by 1                                    C.      decreases by 1
     B.     increases by 2                                    D.      decreases by 2

3.   Which of the following reactions is spontaneous?

     A.     2I- + Ag → Ag+ + I2
     B.     Co2+ + Cu → Co + Cu2+
     C.     Cu2+ + Pb → Pb2+ + Cu
     D.     Ni2+ + 2Ag → 2Ag+ + Ni

4.   Consider the following redox reaction for a lead-acid storage cell:
     Pb + PbO2 + 4H+ + 2SO42- → 2PbSO4 + 2H2O
     The balanced, reduction half reaction is

     A.     Pb +   SO42- → 2PbSO4 + 2e-
     B.     Pb +   2H+ + SO42- → PbSO4 + 2H2O + 2e-
     C.     PbO2   + 4H+ + SO42- + 2e- → 2PbSO4 + 2H2O
     D.     PbO2   + 2SO42 + 2H2O + 2e- → PbSO4 + 2OH-

5.   Consider the following reaction: Cd2+(aq) + Zn(s) → Cd(s) + Zn2+(aq)
     The potential for the reaction is +0.36 V. What is the reduction potential for the cadmium ion?
     A.     -1.12 V                                            C.      +0.40 V
     B.     -0.40 V                                            D.      +1.12 V

6.   Which of the following involves a nonspontaneous redox reaction?

     A.     fuel cell                                         C.      redox titration
     B.     electroplating                                    D.      carbon dry cell

7.   Consider the following redox reaction:
     2MnO4- + 16H+ + 5Sn2+ → 2Mn2+ + 8H2O + 5Sn4+
     In a redox titration, 0.60 mole of KMnO4 reacts completely with a solution of Sn(NO3)2. How
     many moles of Sn(NO3)2 were present in the solution?

     A.     0.024 moles                                       C.      1.5 moles
     B.     0.060 moles                                       D.      0.30 moles



                                                                                                       1
8.    Which of the following is not a redox reaction?

      A.       Cu + Br2 → CuBr2                                 C.       CH4 + H2O → CO2 + 2H2O
      B.       CO + H2O → CO2 + H2                              D.       NaOH + HCl → NaCl + H2O

9.    What is the minimum voltage required to form nickel from an aqueous solution of NiI2 using inert
      electrodes?

A.    0.26 V                B.      0.28 V              C.      0.54 V                D.      0.80 V

10.   What substances are formed at the anode and cathode during electrolysis of molten sodium
      chloride?

               Anode          Cathode

      A.       O2             H2
      B.       Na             Cl2
      C.       Cl2            H2
      D.       Cl2            Na

11.   A solution containing an unknown cation reacts spontaneously with both zinc and copper. The
      unknown cation is

      A.       1.0 M H+                                         C.       1.0 M Sr2+
      B.       1.0 M Ag+                                        D.       1.0 M Mn2+

12.   Which of the following half-reactions are balanced?

      A.       ClO- + H2O + e- → Cl2 + 2OH-
      B.       2ClO- + H2O + 2e- → Cl2 + 3OH-
      C.       2ClO- + 2H2O + 2e- → Cl2 + 4OH-
      D.       2ClO- + 2H2O → Cl2 + 4OH- + 2e-

13.   Which of the following is a spontaneous redox reaction?

      A.       Ag+ + I- → AgI
      B.       Ag+ + Fe2+ → Ag + Fe3+
      C.       3Ag+ + Au → 3Ag + Au3+
      D.       2Ag+ + Ni2+ → 2Ag + Ni

14.   Salting the roads during the winter increases the amount of corrosion of cars. The is because the
      salt

      A.       reacts with the iron                             C.       acts as a reducing agent
      B.       provides an electrolyte                          D.       acts as an oxidizing agent



                                                                                                          2
Consider the following electrochemical cell for the next five questions.

                          voltmeter




                      1.0 M KCl


      Cu                                     Ni




            1M Cu(NO3)2        1M Ni(NO3)2

15.    The half-reaction that occurs at the anode is

       A.         Ni → N2+ + 2e-                                 C.        Cu → Cu2+ + 2e-
       B.         Ni2+ → 2e- + Ni                                D.        Cu2+ → 2e- + Cu

16.    The half-reaction that occurs at the cathode is

       A.         Ni → N2+ + 2e-                                 C.        Cu → Cu2+ + 2e-
       B.         Ni2+ + 2e- → Ni                                D.        Cu2+ + 2e- → Cu

17.    The cell potential or Eo is

A.     0.41 V                         B.     0.78 V       C.     0.34 V                D.    0.60 V

18.    The following ions migrate to the Cu electrode

       A.         K+        Cu2+ Ni2+
       B.         Cu2+      Ni2+
       C.         Cl-       NO3-
       D.         Cl-       NO3- 2e-

19.    The electrons flow

       A.         through the salt bridge from Cu to Ni
       B.         through the salt bridge from Cu to Ni
       C.         through the wire from Cu to Ni
       D.         through the wire from Ni to Cu

20.    Which of the following will not react spontaneously with 1.0 M HCl?

       A.         tin                                            C.        mercury
       B.         lithium                                        D.        magnesium

                                                                                                      3
21.   Which of the following can be produced by electrolysis from a 1.0 M aqueous solution containing
      its ion?

      A.     nickel                                                C.    aluminum
      B.     sodium                                                D.    magnesium


22.   In order for an electrolytic cell to operate, it must have

      A.     a voltmeter.                                          C.    a power supply.
      B.     a salt bridge.                                        D.    an aqueous solution.

23.   In the electrolysis of molten ZnCl2 using carbon electrodes, the reaction that occurs at the anode is

      A.     Zn → Zn2+ + 2e-                                       C.    2Cl- → Cl2 + 2e-
      B.     Zn2+ + 2e- → Zn                                       D.    Cl2 + 2e- → 2Cl-

24.   In the electrolysis of aqueous zinc chloride, the half-reaction at the cathode is

      A.     Cl2 + 2e- → 2Cl-                                      C.    Zn2+ + 2e- → Zn
      B.     2Cl- → Cl2 + 2e-                                      D.    Zn → Zn2+ + 2e-

25.   The corrosion of iron can be prevented by attaching a piece of

      A.     Mn                     B.      Cu                     C.    Pb                     D.   Sn

26.   The oxidation number of carbon in CaC2O4 is

      A.     +2                     B.      +3                     C.    +4                     D.   +6

27.   To plate a nickel coin with copper,

      A.     the nickel coin must be the cathode.
      B.     the cathode must be made out of copper
      C.     the electrons must flow to the anode
      D.     the solution must contain nickel ions




                                                                                                          4
Consider the following electrochemical cell for the next five questions.
                           voltmeter




                       1.0 M KNO3


        Cu                                     Zn




             1M Cu(NO3)2        1M Zn(NO3)2

28.    Which of the following statements apply to this electrochemical cell?

       I        Electrons flow through the wire toward the copper electrode.
       II       The copper electrode increases in mass.
       III      Anions move toward the Zn half-cell.

       A.       I and II only                                    C.        II and III only
       B.       I and III only                                   D.        I, II, and III

29.    The balanced equation for the overall reaction is

       A.       Zn + Cu2+ → Cu + Zn2+
       B.       Cu + Zn2+ → Zn + Cu2+
       C.       Zn2+ + Cu → Cu2+ + Zn
       D.       Cu + Zn → Zn2+ + Cu2+

30.    At equilibrium the voltage of the above cell is

A.     -1.10 V                    B.          0.00 V       C.    +0.42 V                 D.   +1.10 V

31.    This redox reaction occurs because

       A.       Zn is a stronger oxidizing agent than Cu
       B.       Zn is a stronger reducing agent than Cu
       C.       Zn2+ is a stronger oxidizing agent than Cu2+
       D.       Zn2+ is a weaker reducing agent than Cu2+

32.    The initial cell voltage at 25 oC is

       A.       -1.10 V                                          C.        +0.91 V
       B.       +1.10 V                                          D.        +0.86 V




                                                                                                        5
33.   Consider the following redox reaction: Co2+(aq) + 2Ag(s) → 2Ag+(aq) + Co(s)
      The reaction is

      A.     spontaneous and Eo is positive              C.   non-spontaneous and Eo is positive
      B.     spontaneous and Eo is negative              D.   non-spontaneous and Eo is negative

34.   When MnO4- reacts to form Mn2+, the manganese in MnO4- is

      A.     reduced as its oxidation number increases
      B.     reduced as its oxidation number decreases
      C.     oxidized as its oxidation number increases
      D.     oxidized as its oxidation number decreases

35.   The electrolyte used in the alkaline battery is

      A.     KCl                                              C.      H2SO4
      B.     NaOH                                             D.      KOH

36.   The electrolyte used in an automobile battery is

      A.     KCl                                              C.      H2SO4
      B.     NaOH                                             D.      KOH

37.   The anode used in the commercial production of Aluminum is

      A.     C                                                C.      Al
      B.     Pt                                               D.      AL2O3

38.   The anode and cathode used in the electrorefining of impure lead to pure lead are

             Anode                   Cathode

      A.     Pure Pb                 Impure Pb
      B.     Impure Pb               Pure Pb
      C.     Pb2+                    Pb
      D.     Pb                      Pb2+

39.   The anode in the Zinc or common dry cell is

      A.     C                                                C.      Mg
      B.     Zn                                               D.      KOH

40.   Which of the following are electrolytic cells

      I      Electrowinning                                   III     Charging a car battery
      II     Electroplating                                   IV      Fuel cell


      A.     I and II only                                    C.      II and II only
      B.     I, II, and III only                              D.      I, II, III, and IV
                                                                                                   6
Subjective

1.     Balance the following in basic solution.

       MnO4- + C2O42- → MnO2 + CO2 (basic)




2.     Consider the electrolysis of 1.0 M H2SO4 using platinum electrodes.

       a)         Write the oxidation half-reaction


       b)         Write the reduction half-reaction


       c)         Write the overall reaction and determine the minimum theoretical voltage required.


Consider the following diagram for the electrorefinning of lead.


                                  Power Source




        Pure Pb                                           Impure Pb




a)     On the diagram, label the anode and cathode.



b)     Write the formula for a suitable electrolyte



c)     Write the equation for the reduction half-reaction.




                                                                                                       7
4.   Describe two chemically different methods that can be used to prevent corrosion of iron and
     explain why each method works.

     Method 1:

     Explanation:



     Method 2:

     Explanation:



5.   The data below were obtained in a redox titration of a 25.00 mL sample containing Sn2+ ions using
     0.125 M KMnO4 according to the following reaction:
                      2MnO4- + 16H+ + 5Sn2+ → 2Mn2+ + 8H2O + 5Sn4+
                                   Volume of KMnO4 used (mL)

                                   Trial 1        Trial 2       Trial 3

     Initial burette reading       2.00           13.80         24.55
     Final burette reading         13.80          24.55         35.32




6.   A student wanted to electroplate a coin with copper.

a)   Identify a suitable anode


b)   Identify an appropriate electrolyte


c)   To which battery terminal (positive or negative) should the coin be connected?


7.   Consider the electrolysis of molten magnesium chloride.

a)   Identify the product at the anode.


b)   Write the equation for the reduction half-reaction.



                                                                                                    8
c)   Write the equation for the overall reaction.


8.   Consider the following electrochemical cell.

                             voltmeter




                           1.0 M KNO3


        Sn                                     Mn




             1M Sn(NO3)2          1M MnNO3)2




a)   Write the anode reaction


b)   Write the cathode reaction


c)   Write the overall reaction and determine the initial cell potential (Eo).


d)   Explain in words how the electrons move through the cell.


e)   List all of the ions that migrate toward the Sn electrode.


f)   Which electrode loses mass?


g)   What is the purpose of the salt bridge?



h)   What is the cell potential once equilibrium is achieved




                                                                                 9
UNIT 5 REVIEW - SOLUTIONS
1. The following represents the process used to produce iron from iron III oxide:
Fe2O3 + 3CO → 2Fe + 3CO2 What is the reducing agent in this process?

       A.      Fe
       B.      CO
       C.      CO2
       D.      Fe2O3

2. Consider the following reaction: 2HNO2 + 2I- + 2H+ → 2NO + I2 +2H2O
The oxidation number for each nitrogen atom

       A.      increases by 1
       B.      increases by 2
       C.      decreases by 1
       D.      decreases by 2

3. Which of the following reactions is spontaneous?

       A.      2I- + Ag → Ag+ + I2
       B.      Co2+ + Cu → Co + Cu2+
       C.      Cu2+ + Pb → Pb2+ + Cu
       D.      Ni2+ + 2Ag → 2Ag+ + Ni

4. Consider the following redox reaction for a lead-acid storage cell:
Pb + PbO2 + 4H+ + 2SO42- → 2PbSO4 + 2H2O
The balanced, reduction half reaction is

       A.      Pb +    SO42- → 2PbSO4 + 2e-
       B.      Pb +    2H+ + SO42- → PbSO4 + 2H2O + 2e-
       C.      PbO2    + 4H+ + SO42- + 2e- → 2PbSO4 + 2H2O
       D.      PbO2    + 2SO42 + 2H2O + 2e- → PbSO4 + 2OH-

5. Consider the following reaction: Cd2+(aq) + Zn(s) → Cd(s) + Zn2+(aq)
The potential for the reaction is +0.36 V. What is the reduction potential for the cadmium ion?
       A.      -1.12 V
       B.      -0.40 V
       C.      +0.40 V
       D.      +1.12 V

6. Which of the following involves a nonspontaneous redox reaction?

       A.      fuel cell
       B.      electroplating
       C.      redox titration
       D.      carbon dry cell
7. Consider the following redox reaction: 2MnO4- + 16H+ + 5Sn2+ → 2Mn2+ + 8H2O + 5Sn4+

                                                                                                  10
In a redox titration, 0.60 mole of KMnO4 reacts completely with a solution of Sn(NO3)2. How many
moles of Sn(NO3)2 were present in the solution?

       A.     0.024 moles
       B.     0.060 moles
       C.     1.5 moles
       D.     0.30 moles

8. Which of the following is not a redox reaction?

       A.     Cu + Br2 → CuBr2
       B.     CO + H2O → CO2 + H2
       C.     CH4 + H2 → CO2 + 2H2O
       D.     NaOH + HCl → NaCl + H2O

9. What is the minimum voltage required to form nickel from an aqueous solution of NiI2 using inert
electrodes?

       A.     0.26 V
       B.     0.28 V
       C.     0.54 V
       D.     0.80 V

10. What substances are formed at the anode and cathode during electrolysis of molten sodium chloride?

              Anode          Cathode

       A.     O2             H2
       B.     Na             Cl2
       C.     Cl2            H2
       D.     Cl2            Na

11. A solution containing an unknown cation reacts spontaneously with both zinc and copper. The
unknown cation is

       A.     1.0 M H+
       B.     1.0 M Ag+
       C.     1.0 M Sr2+
       D.     1.0 M Mn2+




                                                                                                      11
12. Which of the following half-reactions are balanced?

       A.        ClO- + H2O + e- → Cl2 + 2OH-
       B.        2ClO- + H2O + 2e- → Cl2 + 3OH-
       C.        2ClO- + 2H2O + 2e- → Cl2 + 4OH-
       D.        2ClO- + 2H2O → Cl2 + 4OH- + 2e-

13. Which of the following is a spontaneous redox reaction?

       A.        Ag+ + I- → AgI
       B.        Ag+ + Fe2+ → Ag + Fe3+
       C.        3Ag+ + Au → 3Ag + Au3+
       D.        2Ag+ + Ni2+ → 2Ag + Ni

14. Salting the roads during the winter increases the amount of corrosion of cars. The is because the salt

       A.        reacts with the iron
       B.        provides an electrolyte
       C.        acts as a reducing agent
       D.        acts as an oxidizing agent

Consider the following electrochemical cell for the next five questions.

                         voltmeter




                     1.0 M KCl


      Cu                                    Ni




           1M Cu(NO3)2        1M Ni(NO3)2

15. The half-reaction that occurs at the anode is

       A.        Ni → Ni2+ + 2e-
       B.        Ni2+ → 2e- + Ni
       C.        Cu → Cu2+ + 2e-
       D.        Cu2+ → 2e- + Cu



16. The half-reaction that occurs at the cathode is

       A.        Ni → N2+ + 2e-
       B.        Ni2+ + 2e- → Ni

                                                                                                             12
       C.      Cu → Cu2+ + 2e-
       D.      Cu2+ + 2e- → Cu

17. The cell potential or Eo is

       A.      0.41 V
       B.      0.78 V
       C.      0.34 V
       D.      0.60 V

18. The following ions migrate to the Cu electrode

       A.      K+        Cu2+ Ni2+
       B.      Cu2+      Ni2+
       C.      Cl-       NO3-
       D.      Cl-       NO3- 2e-

19. The electrons flow

       A.      through the salt bridge from Cu to Ni
       B.      through the salt bridge from Cu to Ni
       C.      through the wire from Cu to Ni
       D.      through the wire from Ni to Cu



20. Which of the following will not react spontaneously with 1.0 M HCl?

       A.      tin
       B.      lithium
       C.      mercury
       D.      magnesium

21. Which of the following can be produced by electrolysis from a 1.0 M aqueous solution containing its
ion?

       A.      nickel
       B.      sodium
       C.      aluminum
       D.      magnesium


22. In order for an electrolytic cell to operate, it must have

       A.      a voltmeter.
       B.      a salt bridge.
       C.      a power supply.
       D.      an aqueous solution.

23. In the electrolysis of molten ZnCl2 using carbon electrodes, the reaction that occurs at the anode is
                                                                                                            13
       A.       Zn → Zn2+ + 2e-
       B.       Zn2+ + 2e- → Zn
       C.       2Cl- → Cl2 + 2e-
       D.       Cl2 + 2e- → 2Cl-

24. In the electrolysis of aqueous zinc chloride, the half-reaction at the anode is

       A.       Cl2 + 2e- → 2Cl-
       B.       2Cl- → Cl2 + 2e-
       C.       Zn2+ + 2e- → Zn
       D.       Zn → Zn2+ + 2e-

25. The corrosion of iron can be prevented by attaching a piece of

       A.       Mn
       B.       Cu
       C.       Pb
       D.       Sn

26. The oxidation number of carbon in CaC2O4 is

       A.       +2
       B.       +3
       C.       +4
       D.       +6

27. To plate a nickel coin with copper,

       A.       the nickel coin must be the cathode.
       B.       the cathode must be made out of copper
       C.       the electrons must flow to the anode
       D.       the solution must contain nickel ions




Consider the following electrochemical cell for the next five questions.
                           voltmeter




                       1.0 M KNO3


        Cu                                    Zn




             1M Cu(NO3)2        1M Zn(NO3)2
                                                                                      14
28. Which of the following statements apply to this electrochemical cell?

        I       Electrons flow through the wire toward the copper electrode.
        II      The copper electrode increases in mass.
        III     Anions move toward the Zn half-cell.

        A.      I and II only
        B.      I and III only
        C.      II and III only
        D.      I, II, and III

29. The balanced equation for the overall reaction is

        A.      Zn + Cu2+ → Cu + Zn2+
        B.      Cu + Zn2+ → Zn + Cu2+
        C.      Zn2+ + Cu → Cu2+ + Zn
        D.      Cu2+ + Zn → Zn2+ + Cu

30. At equilibrium the voltage of the above cell is

        A.      -1.10 V
        B.      0.00 V
        C.      +0.42 V
        D.      +1.10 V

31. This redox reaction occurs because

        A.      Zn is a stronger oxidizing agent than Cu
        B.      Zn is a stronger reducing agent than Cu
        C.      Zn2+ is a stronger oxidizing agent than Cu2+
        D.      Zn2+ is a weaker reducing agent than Cu2+

32. The initial cell voltage at 25 oC is

        A.      -1.10 V
        B.      +1.10 V
        C.      +0.91 V
        D.      +0.86 V

33. Consider the following redox reaction: Co2+(aq) + 2Ag(s) → 2Ag+(aq) + Co(s)
The reaction is

        A.      spontaneous and Eo is positive
        B.      spontaneous and Eo is negative
        C.      non-spontaneous and Eo is positive
        D.      non-spontaneous and Eo is negative

34. When MnO4- reacts to form Mn2+, the manganese in MnO4- is

                                                                                  15
       A.      reduced as its oxidation number increases
       B.      reduced as its oxidation number decreases
       C.      oxidized as its oxidation number increases
       D.      oxidized as its oxidation number decreases

35. The electrolyte used in the alkaline battery is

       A.      KCl
       B.      NaOH
       C.      H2SO4
       D.      KOH

36. The electrolyte used in an automobile battery is

       A.      KCl
       B.      NaOH
       C.      H2SO4
       D.      KOH

37. The anode used in the commercial production of Aluminum is

       A.      C
       B.      Pt
       C.      Al
       D.      AL2O3




38. The anode and cathode used in the electrorefining of impure lead to pure lead are

               Anode                    Cathode

       A.      Pure Pb                  Impure Pb
       B.      Impure Pb                Pure Pb
       C.      Pb2+                     Pb
       D.      Pb                       Pb2+

39. The anode in the LeClanche or common dry cell is

       A.      C
       B.      Zn
       C.      Mg
       D.      KOH

40. Which of the following are electrolytic cells

       I       Electrowinning
       II      Electroplating
       III     Charging a car battery
                                                                                        16
IV   Fuel cell

A.   I and II only
B.   I, II, and III only
C.   II and II only
D.   I, II, III, and IV




                           17
Subjective

1.    Balance the following in basic solution.

      MnO4- + C2O42- → MnO2 + CO2 (basic)


      2(MnO4- + 4H+ + 3e- → MnO2 + 2H2O )

      3(C2O42- → 2CO2 + 2e-)

      Acid: 2MnO4- + 3C2O42- + 8H+ → 2MnO2                  + 6CO2 + 4H2O

      Basic: 2MnO4- + 3C2O42- + 4H2O → 2MnO2 + 6CO2 + 8OH-


2.    Consider the electrolysis of 1.0 M H2SO4 using platinum electrodes.

      a)     Write the oxidation half-reaction

      H2O → 1/2O2 + 2H+ + 2e-                     Eo = -0.82 V


      b)     Write the reduction half-reaction

      SO42- + 4H+ + 2e- → H2SO3 + H2O                    Eo = +0.17 V


c)    Write the overall reaction and determine the minimum theoretical voltage required.


      SO42- + 4H+ → 1/2O2 + 2H+ + H2SO3                  Eo = -0.65 V

      MTV = +0.65 V




                                                                                           18
3. Consider the following diagram for the electrorefinning of lead.


                               Power Source



         Cathode                                        Anode
         Pure Pb                                        Impure Pb




a)     On the diagram, label the anode and cathode.



b)     Write the formula for a suitable electrolyte

                        Pb(NO3)2

c)     Write the equation for the reduction half-reaction.

                   Pb2+ + 2e- → Pb(s)



4.     Describe two chemically different methods that can be used to prevent corrosion of iron and
explain why each method works.

       Method 1:              Painting
       Explanation:           Prevents reactants H2O and O2 from contacting the iron


       Method 2:              Attach some Zn


       Explanation:           Fe is forced to be the cathode and cannot oxidize


5.     The data below were obtained in a redox titration of a 25.00 mL sample containing Sn2+ ions using
       0.125 M KMnO4 according to the following reaction:
       2MnO4- + 16H+ + 5Sn2+ → 2Mn2+ + 8H2O + 5Sn4+


                                      Volume of KMnO4 used (mL)
                                                                                                     19
                                      Trial 1         Trial 2       Trial 3

     Initial burette reading         2.00           13.80           24.55
     Final burette reading           13.80          24.55           35.32
                                     11.80          10.75           10.77
                               Average last two to get 10.76 mL
     Calculate the [Sn2+]


     [Sn2+]          =         0.01076 L        x      0.125 mole   x    5 moles Sn2+
                                                       1L                2 moles MnO4-
                                                0.0250 L


                     =         0.135 M

6.   A student wanted to electroplate a coin with copper.

a)   Identify a suitable anode                  Cu



b)   Identify an appropriate electrolyte              CuSO4



c)   To which battery terminal (positive or negative) should the coin be connected?

                                                      Negative

7.   Consider the electrolysis of molten magnesium chloride.

a)   Identify the product at the anode.

                               Cu2+

b)   Write the equation for the reduction half-reaction.

                            Mg2+ +         2e-            Mg(s)
c)   Write the equation for the overall reaction.

Mg2+ +        2Cl-         Mg(s)     +         Cl2

8.   Consider the following electrochemical cell.

                         voltmeter




                     1.0 M KNO3
                                                                                         20
         Sn                                Mn
Cathode                                             Anode




a)   Write the anode reaction

     Sn2+   +       2e-            Sn

b)   Write the cathode reaction

     Mn      Mn2+          +       2e-

c)   Write the overall reaction and determine the initial cell potential (Eo).

     Sn2+   +       Mn                     Mn2+ +          Sn

d)   Explain in words how the electrons move through the cell.

     From anode Mn to cathode Sn

e)   List all of the ions that migrate toward the Sn electrode.

     Sn2+           Mn2+            K+

f)   Which electrode loses mass?

     Anode Sn


g)   What is the purpose of the salt bridge?
     To allow cations and anions to flow from one half cell to the other



h)   What is the cell potential once equilibrium is achieved?
     0.00 v




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posted:10/4/2012
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