Spectroscopic Determination of Iron with Phenanthroline
Experiment A
Spectroscopic determination of Iron with Phenanthroline
Unknown # 2
Mass of Mohr’s Salt: 0.2040
1. 5mL of 6M acetic acid was measured and transferred into a 100mL volumetric flask with a pipette and diluted to the mark.
Concentration = [0.2040(±0.0001)g/100(±0.08)mL]*[(1mol/392.16g)/(1L/1000mL)] = 0.005202(±0.09382%)
= 0.005202(±0.000005)mol/L
2. 10mL of the above stock solution was transferred to a 250 mL volumetric flask and diluted to the mark.
Concentration = [0.005202(±0.09382%)mol/L]*[10(±0.02)mL/250(±0.12mL)] = 0.00020808(±0.22607%) = 0.00020808(±0.0000005)mol/L
3. Standard error of burette is 0.02mL in every reading. Solution | Desired Volume | Absorption 1 | Absorption 2 | Average Absorption | Standard 1 | 30 | 0.662 | 0.664 | 0.662 | Standard 2 | 25 | 0.544 | 0.546 | 0.545 | Standard 3 | 20 | 0.43 | 0.434 | 0.432 | Standard 4 | 15 | 0.317 | 0.309 | 0.313 | Standard 5 | 10 | 0.222 | 0.217 | 0.2195 | Standard 6 | 5 | 0.113 | 0.112 | 0.1125 | Unknown 1 | | | | 0.096 | Unknown 2 | | | | |
4. Sample standard concentration calculation with standard 1,
Concentration = [30(±0.02)mL/100(±0.08)mL]*[0.00020808(±0.0000005)mol/L] = 0.000062424(±0.2807%) = 0.000062424(±0.0000002)
5. From the Calibration curve of Absorbance Vs Concentration, we know the equation of the graph is : y = 10553.63(±190.5558)x - 0.00363(±0.007721)
Where, y is the absorbance and x is the concentration. We know the absorbance of the unknown is 0.096. Therefore,
0.096 = 10553.63(±190.5558)x - 0.00363(±0.007721) x= [0.096+0.00363(±0.007721)]/ [10553.63(±190.5558)] = 0.00000944(±7.957%) = 0.0000094(±0.0000008)
6.
Standard Concentrations | Uncertainties | Average Absorbencies | 0.000062424 | 0.0000002 | 0.662 | 0.00005202 | 0.00000013 | 0.545 | 0.000041616 | 0.000000108 | 0.432 | 0.000031212 | 0.00000007 | 0.313 | 0.000020808 | 0.00000006 | 0.2195 |
Spectroscopic determination of Iron with Phenanthroline
Unknown # 2
Mass of Mohr’s Salt: 0.2040
1. 5mL of 6M acetic acid was measured and transferred into a 100mL volumetric flask with a pipette and diluted to the mark.
Concentration = [0.2040(±0.0001)g/100(±0.08)mL]*[(1mol/392.16g)/(1L/1000mL)] = 0.005202(±0.09382%)
= 0.005202(±0.000005)mol/L
2. 10mL of the above stock solution was transferred to a 250 mL volumetric flask and diluted to the mark.
Concentration = [0.005202(±0.09382%)mol/L]*[10(±0.02)mL/250(±0.12mL)] = 0.00020808(±0.22607%) = 0.00020808(±0.0000005)mol/L
3. Standard error of burette is 0.02mL in every reading. Solution | Desired Volume | Absorption 1 | Absorption 2 | Average Absorption | Standard 1 | 30 | 0.662 | 0.664 | 0.662 | Standard 2 | 25 | 0.544 | 0.546 | 0.545 | Standard 3 | 20 | 0.43 | 0.434 | 0.432 | Standard 4 | 15 | 0.317 | 0.309 | 0.313 | Standard 5 | 10 | 0.222 | 0.217 | 0.2195 | Standard 6 | 5 | 0.113 | 0.112 | 0.1125 | Unknown 1 | | | | 0.096 | Unknown 2 | | | | |
4. Sample standard concentration calculation with standard 1,
Concentration = [30(±0.02)mL/100(±0.08)mL]*[0.00020808(±0.0000005)mol/L] = 0.000062424(±0.2807%) = 0.000062424(±0.0000002)
5. From the Calibration curve of Absorbance Vs Concentration, we know the equation of the graph is : y = 10553.63(±190.5558)x - 0.00363(±0.007721)
Where, y is the absorbance and x is the concentration. We know the absorbance of the unknown is 0.096. Therefore,
0.096 = 10553.63(±190.5558)x - 0.00363(±0.007721) x= [0.096+0.00363(±0.007721)]/ [10553.63(±190.5558)] = 0.00000944(±7.957%) = 0.0000094(±0.0000008)
6.
Standard Concentrations | Uncertainties | Average Absorbencies | 0.000062424 | 0.0000002 | 0.662 | 0.00005202 | 0.00000013 | 0.545 | 0.000041616 | 0.000000108 | 0.432 | 0.000031212 | 0.00000007 | 0.313 | 0.000020808 | 0.00000006 | 0.2195 |