Chmbd221 Potentiometric Halide Titration by hedongchenchen

VIEWS: 8 PAGES: 4

									mL (Ag+) added     mV
     0.51        -318.0
     1.00        -317.5
     1.50        -316.2
     2.01        -314.5
     2.51        -312.5
     3.00        -310.5
     3.51        -309.2
     4.00        -307.2
     4.51        -305.8
     5.00        -304.1
     5.50        -301.5
     6.00        -299.8
     6.52        -297.6
     7.05        -295.5
     7.50        -293.2
     8.04        -291.9
     8.50        -288.9
     9.00        -286.0
     9.50        -284.3
    10.01        -280.5
    10.51        -277.7
    11.00        -275.9
    11.49        -273.1
    12.00        -268.8
    12.50        -265.1
    13.15        -260.0
    14.00        -250.2
    14.50        -241.1
    14.61        -239.0
    14.81        -235.2
    15.05        -230.0
    15.15        -226.0
    15.30        -220.5
    15.61        -200.0
    15.90        -165.0
    15.98        -111.0
    16.05         -44.8
    16.19         -22.0
    16.30          -7.0
    16.50          10.3
    16.76          18.8
    16.80          23.1
    16.99          29.0
    17.24          36.0
    17.55          54.5
    17.70          63.4
    18.05          69.8
    18.50          72.0
    19.00          75.7
    20.00          77.8
    21.01          80.2
22.09    83.1
22.99    84.5
23.99    87.5
24.90    90.6
26.02    95.6
26.94    98.5
27.90   103.6
29.00   108.6
29.70   112.8
30.10   117.3
30.20   118.6
30.38   120.5
30.45   130.2
30.50   133.8
30.60   138.2
30.70   141.8
30.80   147.2
31.00   154.1
31.11   158.4
31.30   164.0
31.40   170.0
31.48   174.8
31.60   184.7
31.64   196.7
31.70   222.0
31.74   250.0
31.80   271.7
31.90   282.7
32.00   300.5
32.04   311.6
32.10   316.7
32.30   325.1
32.50   332.0
32.70   338.8
33.09   343.0
33.49   347.6
34.00   353.0
34.50   358.0
35.00   362.0
35.55   365.3
36.10   368.3
37.11   372.1
38.00   376.3
Heather Sopher CHMBD 221
Potentiometric Halide Titration with Ag+
November 14, 2006

                                             Potentiometric Halide Titration with Ag+
               400.0



               320.0



               240.0



               160.0
Voltage (mV)




                80.0



                  0.0
                    0.00   5.00            10.00      15.00       20.00      25.00      30.00   35.00   40.00

                -80.0



               -160.0



               -240.0



               -320.0
                                                          Volume Ag+ added (mL)
Heather Sopher CHMBD 221
Potentiometric Halide Titration with Ag+
November 14, 2006


Unknown: "Mike Hughes"
Mass of Unknown               1.1671 g

Molarity of Ag+ solution     0.74376 M

Mass KI                       0.8050 g
Mass % KI                     68.97%

Mass KCl                      0.3424 g
Mass % KCl                    27.78%




3.) a.) [Ag+] = 7.0632 x 10-14 after 0.5mL of Ag+ solution added
    b.) [Ag+] = 9.1104 x 10-9 at the equivalence point



4.) ΔmV = 311.0 mV
This value compares to the difference in Ag+ as predicted by the Nernst equation.
311.0/59.2 = 5.25 ≈ 5 mV changes by 59.2 five times from 0.5mL added to equivalence point
There are five factors of 10 in change in [Ag+] from 0.5mL added to equivalence point
7.0632 x 10-14 --> 9.1104 10 -9

Although the values agree very closely, a possible source of error is the loss of original solid Ag2O.
The loss of Ag2O carries through the calculations, eventually affecting the molarity of [Ag+] after
0.5mL of Ag+ solution was added. A lower Ag2O would cause the [Ag+] to be slightly higher, producing
a value that is even closer to being exactly five factors of 10 away from the [Ag+] at the equivalence
point.
Another source of error could be the reading of mV at the equivalence point. The voltage was changing
rapidly, and the mV could be slightly off. If the value were to be more negative, then the change in mV
from 0.5mL added to equivalence point would more closely change by 59.2 mV five times.

								
To top