Experiment 2: Colorimeter
In the experiment a Vernier Colorimeter was used. After some research and lots of calculations and trial experiments the reaction between Vitamin C, Fe3+ and SCN- was found to be a working combination. After the first run of a week, measuring the light absorbed by the [Fe(H2O)5SCN]2+ it was concluded that the results were lacking accuracy. It was decided to repeat the experiment with diluted samples.
A colorimeter measures the absorbance of particular wavelengths of light by a specific solution. How much light is absorbed depends on the concentration of a substance (the amount of moles). This implies that, when the absorbance of an unknown concentration is measured, it is possible to detect the amount of moles …show more content…
Dilute the sample by adding distillate water to the cylinder up to 10 cm3.
8. Pipette 2 cm3 of the twice-diluted Vitamin C Fe3+ solution and 2 cm3 of the SCN- and this to a beaker.
9. Fill one of the other cuvettes with this solution.
10. Put the cuvettes in the colorimeter and record the value. Calibrate the colorimeter after every measurement.
11. Repeat daily.
As the initial amount of Fe3+ is known and the remaining amount of moles is being measured, the difference between these two values is the amount of moles that reacted with Vitamin C. The first day of the experiment (day 0), the concentration of Vitamin C was known, so this value has been added to the calibration curve. As the concentration of Vitamin C of the first day was a known concentration, the calibration curve was only a double check and the calculations where derived of the first day in order to minimalize systematic errors.
Results
Table 5.0: DATA COLLECTION of the colorimeter values when diluted once
Value Colorimeter
[(± 0,001), diluted once]
Time
[day] Lowest Value Obtained (-) Highest Value Obtained (+) Used Value* (± 0,001)
1 1,827 1,835 1,831
2 1,870 1,878 1,874
3 1,952 1,960 1,956
4 1,977 1,985 1,981
5 2,029 2,037 2,033
6 2,082 2,090 …show more content…
The value used was the value that was shown for the longest time. Reasons for this deviation might be small amounts of a substance so that it was hard to measure or inaccurate apparatus. It is important to note that these deviations are relatively small as they occurred in the second decimal point; therefore the measurements are vastly accurate.
The use of pipettes might have caused inaccuracies in the volumes used, as some part of the substance might have stayed behind in the pipette. Instead of using a pipette a small measuring cylinder can be utilized to measure the volume more accurately.
After the dilution of the Vitamin C sample unwanted substances of the water can react with Fe3+ causing the results to be inaccurate. This error cannot be prevented however by using the ‘known’ value of the first day in your calculations, the accuracy of the results can be checked and systematic errors can be eradicated. Experiment 3: pH
The word ‘acid’ in ascorbic acid is a reference for a
In the experiment a Vernier Colorimeter was used. After some research and lots of calculations and trial experiments the reaction between Vitamin C, Fe3+ and SCN- was found to be a working combination. After the first run of a week, measuring the light absorbed by the [Fe(H2O)5SCN]2+ it was concluded that the results were lacking accuracy. It was decided to repeat the experiment with diluted samples.
A colorimeter measures the absorbance of particular wavelengths of light by a specific solution. How much light is absorbed depends on the concentration of a substance (the amount of moles). This implies that, when the absorbance of an unknown concentration is measured, it is possible to detect the amount of moles …show more content…
Dilute the sample by adding distillate water to the cylinder up to 10 cm3.
8. Pipette 2 cm3 of the twice-diluted Vitamin C Fe3+ solution and 2 cm3 of the SCN- and this to a beaker.
9. Fill one of the other cuvettes with this solution.
10. Put the cuvettes in the colorimeter and record the value. Calibrate the colorimeter after every measurement.
11. Repeat daily.
As the initial amount of Fe3+ is known and the remaining amount of moles is being measured, the difference between these two values is the amount of moles that reacted with Vitamin C. The first day of the experiment (day 0), the concentration of Vitamin C was known, so this value has been added to the calibration curve. As the concentration of Vitamin C of the first day was a known concentration, the calibration curve was only a double check and the calculations where derived of the first day in order to minimalize systematic errors.
Results
Table 5.0: DATA COLLECTION of the colorimeter values when diluted once
Value Colorimeter
[(± 0,001), diluted once]
Time
[day] Lowest Value Obtained (-) Highest Value Obtained (+) Used Value* (± 0,001)
1 1,827 1,835 1,831
2 1,870 1,878 1,874
3 1,952 1,960 1,956
4 1,977 1,985 1,981
5 2,029 2,037 2,033
6 2,082 2,090 …show more content…
The value used was the value that was shown for the longest time. Reasons for this deviation might be small amounts of a substance so that it was hard to measure or inaccurate apparatus. It is important to note that these deviations are relatively small as they occurred in the second decimal point; therefore the measurements are vastly accurate.
The use of pipettes might have caused inaccuracies in the volumes used, as some part of the substance might have stayed behind in the pipette. Instead of using a pipette a small measuring cylinder can be utilized to measure the volume more accurately.
After the dilution of the Vitamin C sample unwanted substances of the water can react with Fe3+ causing the results to be inaccurate. This error cannot be prevented however by using the ‘known’ value of the first day in your calculations, the accuracy of the results can be checked and systematic errors can be eradicated. Experiment 3: pH
The word ‘acid’ in ascorbic acid is a reference for a