The calibration curve observed in this investigation was the relationship measured between the concentration of the cobalt solution, or CO(NO3)2, and the absorbance of the wavelength. As it was impossible to measure the true standard curve, the data points and subsequent graphs demonstrated the qualitative information collected and the trend of these values. The calibration curve closely resembled a straight line, with only minimal deviations in either direction. This indicated that the solutions examined and the data attained had a low percentage of error and high accuracy. As the concentration of the cobalt (II) solution decreased, the absorbance also decreased. This direct proportional relationship, explicated by Beer-Lambert’s Law
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The more obvious and likely was the contamination by over-dilution of the known solution. Despite proper laboratory methods, the possibility of excess DI water or remnants of the previous concentration of the solution being retained in the vessels as they were mixed and transferred from pipette to graduated cylinder to glass test tube, is high. Consequently, in order to decrease this in future investigations, it would be advisable to use a separate pipette and graduated cylinder for each of the ten solutions. Other possible sources of error, not necessarily a factor in this experiment, included: utilizing dirty glassware and cuvettes, using tap water which contains contaminating ions, and not calibrating the spectrophotometer/colorimeter. Limitations to this procedure were that the measurement of cobalt in the soil is only theoretical in this instance, as the investigation does not include any actual soil samples. Furthermore, an aqueous solution and heterogeneous mixed solid would not be realistically comparable to the novice chemist, using the spectrophotometer/colorimeter technique. Other possible limitations, not necessarily a factor in this investigation, included: imprecise volume measurements, incorrect molar calculations, and utilizing the wrong prepared cobalt solution (with unknown concentration).
As defined in the lab manual, there was not enough cobalt in the tested soil samples. For
The more obvious and likely was the contamination by over-dilution of the known solution. Despite proper laboratory methods, the possibility of excess DI water or remnants of the previous concentration of the solution being retained in the vessels as they were mixed and transferred from pipette to graduated cylinder to glass test tube, is high. Consequently, in order to decrease this in future investigations, it would be advisable to use a separate pipette and graduated cylinder for each of the ten solutions. Other possible sources of error, not necessarily a factor in this experiment, included: utilizing dirty glassware and cuvettes, using tap water which contains contaminating ions, and not calibrating the spectrophotometer/colorimeter. Limitations to this procedure were that the measurement of cobalt in the soil is only theoretical in this instance, as the investigation does not include any actual soil samples. Furthermore, an aqueous solution and heterogeneous mixed solid would not be realistically comparable to the novice chemist, using the spectrophotometer/colorimeter technique. Other possible limitations, not necessarily a factor in this investigation, included: imprecise volume measurements, incorrect molar calculations, and utilizing the wrong prepared cobalt solution (with unknown concentration).
As defined in the lab manual, there was not enough cobalt in the tested soil samples. For