Chemical Reaction End Point Timer. - page 4
Keywords: Physics Chemistry Practical Build device end point timer
By Jenny on 02/07/2009
Level: A Level (Year 13)
Page Number: 4 of 9 pages: 1 2 3 4 5 6 7 8 9
the average of these three for my results, this should minimise error, also if one set of results was very different to the other two I would know something might have gone wrong in that experiment.
Finally I did a last preliminary experiment; a test run the same as my final experiment to make sure there were no problems.
Diagram of practical set-up
Circuit Diagram
Apparatus
Hydrochloric acid (0.5M, 1M, 1.5M, 2M and 2.5M)
Sodium thiosulphate (0.25M)
LED (with integrated resistor)
LDR
Resistor (10kΩ)
Cover (made of black paper, built around apparatus)
Clamps
Stand
Test tube
Pipette (3ml)
Pipette filler
Beakers (25ml)
Wires
Crocodile clips
Power pack (use 12V setting)
Voltmeter (measuring accurately between at least 0.01 and 10V)
Stopwatch
Step by step instructions for experiment.
1. Connect circuits
2. Pour out HCl into beaker
3. Pour out Na²S²O² into beaker
4. Pipette out 3ml of HCl and pour into test tube
5. Pipette out 3ml of Na²S²O² and pour into test tube – easiest if you get some else to do this as at the same time you start the stopwatch
6. Take readings every 10 seconds for 300 seconds
7. Repeat 3 times for each concentration
Results
Preliminary experiment 1
This experiment, judging by eye when the reaction between 25ml of Na2S2O3 (0.25M) & 25ml of HCl (1M) finished, was primarily to gain a rough idea of how fast the chemicals reacted for future experiments.
End Point – 36.73 seconds
Preliminary Experiment 2
This was a reaction between 3ml of Na2S2O3 (0.25M) & 3ml of HCl (1M), measuring the voltage every 5 seconds from 0 seconds. Recording every 5 seconds was difficult so I only recorded for 180 seconds.
Time, t, (s) Potential difference across fixed resistor, V, (V)
0 5.29
5 4.74
10 -
15 4.66
20 4.60
25 4.46
30 4.27
35 4.06
40 -
45 3.54
50 3.33
55 -
60 3.08
65 2.92
70 2.83
75 2.81
80 2.74
85 2.69
90 2.65
95 2.59
100 2.57
105 2.55
110 2.53
115 2.52
120 2.45
125 2.41
130 2.40
135 2.42
140 2.40
145 2.43
150 2.38
155 2.29
160 2.31
165 2.44
170 2.45
175 2.46
180 2.46
Preliminary Experiment 3
Again a reaction between 3ml of Na2S2O3 (0.25M) & 3ml of HCl (1M), this time measuring the voltage every 10 seconds from 0 seconds.
Time, t, (s) Potential difference across fixed resistor, V, (V)
0 5.14
10 5.14
20 5.13
30 4.92
40 4.32
50 3.50
60 3.20
70 2.90
80 2.78
90 2.76
100 2.65
110 2.59
120 2.46
130 2.43
140 2.51
150 2.51
160 2.49
170 2.46
180 2.45
190 2.43
200 2.41
210 2.40
220 2.38
230 2.37
240 2.36
250 2.35
260 2.34
270 2.35
280 2.35
290 2.35
300 2.35
The following tables and graph are my official results, the reactions are all between 3ml of Na2S2O3 (0.25M) & 3ml HCl (0.5, 1, 1.5 & 2M), measuring the voltage every 10 seconds from 0 seconds.
Results for 0.5M
Time, t, (s) Potential difference across fixed resistor, V, (V)
Readings 1 Readings 2 Readings 3 Readings Average
0 5.43 5.48 5.39 5.43
10 5.39 5.48 5.40 5.42
20 5.40 5.49 5.40 5.43
30 5.40 5.48 5.37 5.42
40 5.20 5.31 5.21 5.24
50 4.82 4.86 4.68 4.79
60 4.35 4.36 4.33 4.35
70 4.01 3.99 4.00 4.00
80 3.85 3.82 3.84 3.84
90 3.76 3.73 3.75 3.75
100 3.70 3.68 3.70 3.69
110 3.66 3.65 3.67 3.66
120 3.63 3.62 3.65 3.63
130 3.60 3.60 3.62 3.61
140 3.55 3.59 3.61 3.58
150 3.57 3.58 3.60 3.58
160 3.54 3.57 3.59 3.57
170 3.53 3.56 3.57 3.55
180 3.52 3.55 3.57 3.55
190 3.48 3.53 3.57 3.53
200 3.51 3.53 3.56 3.53
210 3.50 3.53 3.56 3.53
220 3.50 3.52 3.54 3.52
230 3.49 3.52 3.53 3.51
240 3.48 3.52 3.52 3.51
250 3.48 3.52 3.51 3.50
260 3.48 3.51 3.47 3.49
270 3.47 3.51 3.50 3.49
280 3.46 3.51 3.50 3.49
290 3.46 3.50 3.49 3.48
300 3.45 3.50 3.49 3.48
Judging by eye
End Point – 140 seconds
Results for 1M
Time, t, (s) Potential difference across fixed resistor, V, (V)
Readings 1 Readings 2 Readings 3 Readings Average
0 5.41 5.42 5.43 5.42
10 5.41 5.37 5.43 5.40
20 5.41 5.37 5.43 5.40
30 5.32 5.30 5.30 5.31
40 4.60 5.03 4.52 4.72
50 3.72 4.32 3.28 3.77
60 3.05 3.62 2.67 3.11
70 2.72 3.04 2.40 2.72
80 2.56 2.71 2.25 2.51
90 2.46 2.55 2.10 2.37
100 2.39 2.44 2.05 2.29
110 2.35 2.35 2.04 2.25
120 2.32 2.25 2.00 2.19
130 2.30 2.23 1.96 2.16
140 2.27 2.19 1.93 2.13
150 2.23 2.15 1.91 2.10
160 2.20 2.12 1.89 2.07
170 2.18 2.09 1.87 2.05
180 2.15 2.07 1.86 2.03
190 2.13 2.05 1.84 2.01
200 2.11 2.04 1.84 2.00
210 2.11 2.03 1.83 1.99
220 2.10 2.02 1.82 1.98
230 2.09 2.01 1.81 1.97
240 2.09 2.01 1.81 1.97
250 2.10 2.00 1.81 1.97
260 2.12 2.00 1.80 1.97
270 2.10 1.99 1.80 1.96
280 2.09 1.98 1.80 1.96
290 2.08 1.99 1.79 1.95
300 2.08 1.98 1.80 1.95
Judging by eye
End Point – 96 seconds
Results for 1.5M
Time, t, (s) Potential difference across fixed resistor, V, (V)
Readings 1 Readings 2 Readings 3 Readings Average
0 5.42 5.44 5.42 5.43
10 5.42 5.45 5.43 5.43
20 5.43 5.45 5.42 5.43
30 5.41 5.42 5.42 5.42
40 5.28 5.23 5.42 5.31
50 5.14 4.75 5.39 5.09
60 4.66 4.06 5.33 4.68
70 4.12 3.52 5.21 4.28
80 3.50 3.28 5.04 3.94
90 3.18 3.12 4.81 3.70
100 3.00 3.03 4.50 3.51
110 2.88 2.95 4.19 3.34
120 2.80 2.89 3.85 3.18
130 2.74 2.84 3.62 3.07
140 2.69 2.80 3.38 2.96
150 2.65 2.76 3.24 2.88
160 2.62 2.70 3.12 2.81
170 2.59 2.67 3.01 2.76
180 2.56 2.60 2.93 2.70
190 2.55 2.63 2.87 2.68
200 2.53 2.62 2.82 2.66
210 2.51 2.64 2.77 2.64
220 2.49 2.60 2.73 2.61
230 2.48 2.62 2.69 2.60
240 2.47 2.61 2.66 2.58
250 2.46 2.60 2.63 2.56
260 2.46 2.59 2.60 2.55
270 2.46 2.59 2.58 2.54
280 2.45 2.58 2.56 2.53
290 2.41 2.57 2.53 2.50
300 2.45 2.57 2.52 2.51
Judging by eye
End Point – 91 seconds
Results for 2M
Time, t, (s) Potential difference across fixed resistor, V, (V)
Readings 1 Readings 2 Readings 3 Readings Average
0 5.48 5.48 5.39 5.45
10 5.48 5.49 5.40 5.46
20 5.48 5.49 5.40 5.46
30 5.48 5.43 5.29 5.40
40 5.44 4.96 4.89 5.10
50 5.40 4.02 4.03 4.48
60 5.25 3.27 3.46 3.99
70 4.95 2.95 3.21 3.70
80 4.54 2.80 3.12 3.49
90 4.14 2.71 3.06 3.30
100 3.77 2.65 3.02 3.15
110 3.50 2.60 2.98 3.03
120 3.32 2.56 2.92 2.93
130 3.20 2.53 2.87 2.87
140 3.11 2.51 2.83 2.82
150 3.05 2.49 2.82 2.79
160 2.99 2.48 2.84 2.77
170 2.95 2.46 2.84 2.75
180 2.90 2.45 2.83 2.73
190 2.88 2.44 2.82 2.71
200 2.85 2.43 2.81 2.70
210 2.82 2.42 2.81 2.68
220 2.80 2.41 2.79 2.67
230 2.77 2.41 2.80 2.66
240 2.75 2.40 2.79 2.65
250 2.73 2.40 2.78 2.64
260 2.72 2.35 2.72 2.60
270 2.76 2.35 2.72 2.61
280 2.68 2.39 2.72 2.60
290 2.67 2.38 2.77 2.61
300 2.66 2.38 2.78 2.61
Judging by eye
End Point –
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