Chapter 7 Electrochemistry - Shandong Example: The conductivity of a saturated AgCl solution is 1.86

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Transcript of Chapter 7 Electrochemistry - Shandong Example: The conductivity of a saturated AgCl solution is 1.86

  • Chapter 7 Electrochemistry

    §7.3 Applications of Conductivity Measurement

  • 1. Monitor the purity of water

    Silicon wafer

    Integrated circuit

    Fabrication of VLSI

    §7.3 Applications of Conductivity Measurement

  • 1. Monitor the purity of water Fabrication of VLSI

    §7.3 Applications of Conductivity Measurement

    Silicon wafer

  • In-situ monitoring of the cleaning

    process: H2O2/H2SO4 → DW rinse →

    dilute HF → SC-1 cleaning → DW

    rinse → hot DW rinse → DW rinse →

    SC-2 cleaning → DW rinse → dilute

    HF → DW rinse.

    DW⎯deionized water,

    SC ⎯ standard cleaning:

    SC-1: H2O2/NH3; SC-2: H2O2/HCl.

    1. Monitor the purity of water Fabrication of VLSI

    water Tap

    water

    Distilled

    water

    Deionized

    water

    Pure

    water

    /S·m-1 1 10-2 ~1 10-3

  • 2. Measure the ionizability and dissociation constant

    m

    ( )c Z F U U

    c  + + + −

    + =

    c+ =c

    m ( )U U F  + −= +

    At infinite dilution

    m ( )F U U   

    + −= +

    m

    m

    ( )

    ( )

    U U F

    U U F

      

     + −

      

    + −

    + = =

    +

    Arrhenius suggested that the degree of

    dissociation of an electrolyte can be

    calculated using molar conductivity.

    §7.3 Applications of Conductivity Measurement

  • 22 2 2

    m

    m m m(1 ) 1 ( )

    cc c K

    c

     

          = = =

    − − −

    Ostwald dilution law

    Ostwald showed how one can measure the

    dissociation constant of an acid.

    The equation can be rearranged to

    m2

    m m m

    1 1 1 ( )

    a

    c K

        

    = +

    Linearization

    2. Measure the ionizability and dissociation constant

    §7.3 Applications of Conductivity Measurement

  • 3. Determine solubility and solubility products

    -Ag Ag Cl Cl H H OH OH c c c c    + + − + + − −= + + +

    w Ag Ag Cl Cl Ag Cl ( )c c S     + + − − + −− = + = +

    w w

    mAg Cl

    S    

      + − 

    − − = =

    +

    Example: The conductivity of a saturated

    AgCl solution is 1.86  10-4 S·m-1, while

    that of water used for preparation the

    solution is 6.0  10-6 S·m-1. Given that the

    molar conductivity of AgCl is 0.01372

    S·mol-1·m2. Calculate the solubility

    product for AgCl. What assumption have we made?

    §7.3 Applications of Conductivity Measurement

  • 4. Determine ion product of water

    Water can be taken as a dilute solution

    of a strong electrolyte

    CH+ = COH- = Kw 1/2

    m m,H m,OHc

       + −

      = = +

    The specific conductance of highly purified

    water is 5.478 10-6 S·m-1. Calculate the

    concentration of hydrogen ion in water.

    -1 2

    m m,H m,OH 0.05481S mol m  + −

      = + =  

    6 1

    1 2

    m

    4 3

    7 3

    5.478 10 S m

    0.05481S mol m

    0.9995 10 mol m

    1 10 mol dm

    c 

    − −

     −

    − −

    − −

      = =

     

    =  

      

    §7.3 Applications of Conductivity Measurement

  • 5. Conductometric titration (the way to determine endpoint)

    The conductance variation of a solution

    during titration can serve as a useful

    method to follow the course of the

    reaction.

    Na+ + OH- + (HCl) = Na+ + Cl- + (H+ + Cl-)

    5.19 20.52 5.19 7.91 36.30

    Precipitation reactions,

    neutralization reactions,

    coordination reactions

    A

    B

    C

    A’

    B’

    C’

    V / ml

     /

    S ·m

    -1

    endpoint

    §7.3 Applications of Conductivity Measurement

  • 5. Conductometric titration

    §7.3 Applications of Conductivity Measurement

  • 6. Study on ionic channel in cell membrane

    §7.3 Applications of Conductivity Measurement

  • 6. Study on ionic channel in cell membrane

    §7.3 Applications of Conductivity Measurement