Spectroscopic Determination of Nickel.docx - Spectroscopic...

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Spectroscopic Determination of Nickel (II)Chem120-8530
Purpose: A Spectronic20D was used to measure the wavelengths of known and unknown concentrations of Nickel (II) ions. The absorbance of the four known concentrations of NiSO4 were used to construct Beer’s Law plots at different wavelengths, which were used to determine the concentrations of an unknown solution of NiSO4.Introduction:The wavelength of visible light ranges from approx. 400-700nm on the electromagnetic spectrum. The color of visible light is determined by its wavelength, which results from an electron moving from one energy state to another. As the electron of an atom moves between its ground and excited state, the energy difference results in different wavelengths. Larger energy differences result in shorter wavelengths, closer to the violet end of the visible light spectrum, and smaller energy differences result in long wavelengths, closer to the red end of the visible light spectrum. In an absorbance spectrum, which plots the wavelength vs absorbance of a substance, the peaks correspond to the excitation of an electron from the ground to excited state energy level. These points where electrons can be excited into from the ground state are where radiation can be absorbed. The peaks for an absorbance spectrum of 0.1M NiSO4fall at wavelengths 395nm, 658nm, and 722nm. Absorption spectrometers measure absorbances at given wavelengths. This, and a resulting Beer’s Law plot, allows for the determination of concentrations of substances since the amount of light absorbed by the sample depends on the concentration of a substance in the sample. ABeer’s Law plot can be created by measuring the absorbances of solutions of known concentrations, at a specific wavelength. According to Beer’s Law, the absorbance of a solution 1
at a given wavelength is directly proportional to its concentration and the distance the light travels through the solution. This is shown in the equation |¿|ϵλbC, where ‘Abs’ is the
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