Investigating The Ph With Potentiometric Measurement Using A Ph Meter And Electrode

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pH measurements and their application

Purpose: The motive of this experiment is to determine the pH with potentiometric measurement using a pH meter and electrode.
Procedure: In this lab we worked with several compounds, and we titrated an unknown weak acid as well as a known amount of potassium hydrogen phthalate. On day one we were tasked with filling several test tubes with a few milliliters of various solutions (pH 7, HCl, deionized water, H3BO3 NaHCO3, etc.) and evaluating the pH of each substance (refer to table I). The pH was evaluated using a pH meter as well as an electrode. Before the evaluation was performed, the pH meter/ electrode were calibrated using the instructions given in the box. The calibration was necessary in order
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4%
9
0.10M NaHCO3
9.68
8.05
16.84%
10
Na2CO3, NaHCO3 (equal volumes)
10.25
9.16
10.63%
11
Buffer pH 7
7.02
7.00
0.28%
12
Buffer pH 4
4.03
4.01
0.50%

Table II
Mass KHP (g)
Vi NaOH (mL)
Vf NaOH (mL)
Trial 1
0.418 g
5.27 mL
25.30 mL
Trial 2
0.423g
25.48 mL
45.67 mL
Trial 3
N/A
N/A
N/A

Table 3
-Trial 1 (NaOH to unknown weak acid)
Buret Reading [mL] mL NaOH Added pH Average Volume
((pH2-pH1)/(V2-V12))
0.00
0.00
1.89

3.50
3.50
2.67
1.75
0.22286
6.72
6.72
3.54
5.11
0.27019
9.72
9.72
3.70
8.22
0.05333
12.50
12.50
3.90
11.11
0.07194
15.60
15.60
4.16
14.05
0.08387
18.54
18.54
4.50
17.07
0.11565
21.50
21.50
4.80
20.02
0.10135
23.52
23.52
7.68
22.51
1.42574
24.50
24.50
10.14
24.01
2.51020
27.56
27.56
10.80
26.03
0.21569
30.58
30.58
11.76
29.07
0.31788
33.58
33.58
11.91
32.08
0.05000
36.69
36.69
12.04
35.14
0.04180

-Trial 2 (NaOH with unknown weak acid)

mL NaOH Added pH Average Volume
((pH2-pH1)/(V2-V12))
0.00
2.78

3.00
2.52
1.50
-0.0867
5.90
3.79
4.45
0.4379
9.20
4.11
7.55
0.0970
12.02
4.37
10.61
0.0922
15.00
4.57
13.51
0.0671
16.10
4.64
15.55
0.0636
17.20
4.69
16.65
0.0455
18.00
4.98
17.60
0.3625
19.00
4.61
18.50
-0.3700
20.10
4.75
19.55
0.1273
21.05
4.90
20.58
0.1579
22.00
5.15
21.53
0.2632
23.00
5.69
22.50
0.5400
23.27
5.83
23.14
0.5185
23.48
6.16
23.38
1.5714
23.72
7.84
23.60
7.0000
27.03
11.15
25.38
1.0000
30.19
11.41
28.61
0.0823
33.05
11.56
31.62
0.0524
36.10
11.66
34.58
0.0328
39.10
11.77
37.60
0.0367
44.20
11.87
41.65
0.0196

-Calculations:
A)
There are

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