Nguyen Khac Duy K4/01-AP
The Laboratory Report
I. Experiment 6 – Strong acid-strong base titration:
1. Purpose:
- The solutions we prepare in the strong acid-strong base experiment will be used as standardized solutions when we explore the additional complexities of a weak-acid titration curve experiment and the titration of a polyprotic acid experiment.
- Draw the strong acid-strong base titration curve
- Calculate the initial concentration of HCl
- Chemical reactions in the experiment:
H+ + OH- -> H2O
NaOH + HCl -> NaCl + H2O
2. Procedure:
- Step 1: Clean and dry all equipment especially the pH meter.
- Step 2: Take 10mL of HCl solution in small beaker, add 40 mL of distilled water and 3 drops of phenolphthalein. Then put the beaker on the pH meter.
- Step 3: Take 0.1M NaOH solution in small beaker, then pour it into Volumetric Buret.
- Step 4: Turn on the pH meter, record the initial value of pH in the report.
- Step 5: Add each of 5mL NaOH solution into beaker containing HCl solution until pH jump fastly.
- Step 6: After the pH jump quickly, add each of 2mL NaOH solution until pH > 11, then the process stops.
Note: Remember to record the results of pH after each addition of base.
3. Data and Observations:
VNaOH added (mL)
pH value
VNaOH added (mL)
pH value

0.00
2.04
7.00
2.61

0.50
2.04
7.50
2.71

1.00
2.05
8.00
2.81

1.50
2.09
8.50
2.91

2.10
2.09
9.00
3.16

2.50
2.14
9.50
3.62

3.00
2.19
9.70
4.00

3.50
2.19
9.90
6.75

4.00
2.25
9.95
7.20

4.50
2.30
10.00
9.02

5.00
2.35
10.20
10.22

5.50
2.40
10.50
11.24

6.00
2.45
10.70
11.32

6.50
2.50
10.90
11.60

4. Make the titration curve:
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5. Calculations:
Suppose CM of HCl is 𝑥 M
When we mix 40 mL pure water and 10 mL HCl 𝑥 M, so we have a
𝑥
5 M HCl solution.
Consider 50 mL HCl
𝑥
5 M + y mL NaOH 0.1M
The mole of HCl is
𝑥
5
50
1000
𝑥
100 mol
The mole of NaOH is 0.1
𝑦
1000
𝑦
10000 mol
If pH <7, so HCl is in excess.
nHCl in excess =
𝑥
100−
𝑦
10000 mol
[H+] = CM (HCl in excess) =
𝑥
100−
𝑦
10000
50+𝑦
1000=
10𝑥−
𝑦
10
50+𝑦 M
We have [H+] =
10−𝑝𝐻

=> 𝑥=
10−𝑝𝐻
50+𝑦+
𝑦
10
10 M
We have table:
VNaOH added (mL)
pH value
 CM HCl
VNaOH added (mL)
pH value
 CM HCl

0
2.04
0.0456
7
2.61
0.0840

0.5
2.04
0.0511
7.5
2.71
0.0862

1
2.05
0.0555
8
2.81
0.0890

1.5
2.09
0.0569
8.5
2.91
0.0922

2.1
2.09
0.0633
9
3.16
0.0941

2.5
2.14
0.0630
9.5
3.62
0.0964

3
2.19
0.0642
9.7
4
0.0976

3.5
2.19
0.0695
9.9
6.75
0.0990

4
2.25
0.0704
9.95