Determination Of The Quantity Of KI And

Topics: Titration, Integral, Equivalence point Pages: 7 (796 words) Published: December 3, 2014

I. Determination of the Quantity of KI and KCl salts by Potentiometric Halide Titration II. Executive Summary
The goal of this experiment is to determine the quantity of KI and KCl salts in an unknown mixture by potentiometric titration with . Potentiometric halide titration can be used to determine the composition of an unknown when there is more than one salt present in the mixture. The first end point is located by drawing appropriate lines tangent to the first titration curve and the second end point is determined by the second derivative of the titration curve. The determined amounts of the salts in the unknown mixture are as follows; 0.5975 g KI and 0.3010 g KCl. The weight percent was calculated to be 8.12%.

III. Methods
Refer to page 71 of Harris QCA Experiments PDF supplement to QCA, Harris, 8th Edition, 2010 for procedure. Modifications: Complete one rough titration and one precise titration, range for KCl is 0.20-0.40 g and range for KI is 0.50-0.70 g. Specific lab equipment used: pH meter 8, burette S, 25 mL pipette A831, 100 mL volumetric flask A831 and A001 (used for silver nitrate solution), balance #5, unknown vial 2. IV. Results

Bisulfate Buffer with a pH of 2:

Reactions:

Determining which Precipitates first:

AgI precipitates first since its solubility product is less than that of AgCl. Determination of mass of KI:
Mass = 1.2046 g
Mass corrected = 1.2046 g 1.011= 1.2179 g

Determination of Mass of KCl:

Total Mass KCl and KI:

Calibrated Glassware

100 mL vol. flask A831
25 mL pipette A831
100 mL vol. flask A001
Actual Volume
99.97 mL
24.97 mL
99.96 mL
Standard Deviation
0.02
0.03
0.11

Buoyancy Corrections @ 25°C

Unknown
AgNO3
Mass
0.9674 g
1.2046 g
Mass Corrected
0.9780 g
1.2179 g

1st Derivative
2nd Derivative
Volume Titrant (mL)
Vol. Titrant Corrected mL (Onswega's Buret S Graph)
Measured mV
mL AgNO3 (initial+final)/2
delta mV/ delta V
mL AgNO3 from first derivative (initial+final)/2
delta(delta mV/ delta V)/delta V
0.00
0.00
480
0.48
-3.16E+00
0.97
2.75E-01
0.95
0.95
477
1.47
-2.88E+00
2.01
-6.69E-01
1.99
1.99
474
2.55
-3.60E+00
3.06
-6.84E-01
3.10
3.10
470
3.57
-4.30E+00
4.07
-2.83E-01
4.03
4.03
466
4.58
-4.59E+00
5.07
4.23E-02
5.12
5.12
461
5.56
-4.55E+00
6.07
-1.52E+00
6.00
6.00
457
6.58
-6.09E+00
7.09
4.60E-01
7.15
7.15
450
7.60
-5.62E+00
8.07
-2.33E+00
8.04
8.04
445
8.55
-7.84E+00
9.06
-3.13E+00
9.06
9.06
437
9.56
-1.10E+01
10.07
-4.47E+00
10.06
10.06
426
10.58
-1.55E+01
10.91
-1.53E+01
11.09
11.09
410
11.25
-2.58E+01
11.36
3.43E+00
11.40
11.40
402
11.48
-2.50E+01
11.55
-5.95E+01
11.56
11.56
398
11.62
-3.33E+01
11.73
6.50E+01
11.68
11.68
394
11.84
-1.94E+01
11.95
-2.27E+02
11.80
11.99
388
12.06
-6.92E+01
12.15
-2.68E+02
11.94
12.12
379
12.24
-1.17E+02
12.33
-2.92E+02
12.18
12.35
352
12.42
-1.71E+02
12.47
-1.50E+04
12.32
12.49
328
12.51
-1.53E+03
12.54
1.14E+04
12.36
12.53
267
12.57
-9.00E+02
12.60
1.16E+04
12.43
12.60
204
12.64
-8.57E+01
12.69
5.37E+02
12.50
12.67
198
12.75
-2.67E+01
13.00
1.17E+01
12.66
12.82
194
13.26
-2.07E+01
13.68
8.46E+00
13.55
13.69
176
14.10
-1.36E+01
14.56
-9.11E-01

1st Derivative
2nd Derivative
Volume Titrant (mL)
Vol. Titrant Corrected mL (Onswega's Buret S Graph)
Measured mV
mL AgNO3 (initial+final)/2
delta mV/ delta V
mL AgNO3 from first derivative (initial+final)/2
delta(delta mV/ delta V)/delta V
14.48
14.50
165
15.02
-1.44E+01
15.53
1.15E+00
15.54
15.54
150
16.03
-1.33E+01
16.55
4.79E+00
16.52
16.52
137
17.06
-8.33E+00
17.57
6.14E+00
17.60
17.60
128
18.08
-2.11E+00
18.63
-9.41E-01
18.55
18.55
126
19.19
-3.15E+00
19.80
-1.62E+00
19.82
19.82
122
20.41
-5.13E+00
20.96
5.45E+00...
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