Chemistry Lab Report

Chemistry Lab Report




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Abstract
The concentration of unknown solutions can be determined by following a series of Spectrophotometric steps of a simple procedure, followed by data analysis. in which a series of steps are followed Lab #1 experiment (Absorption spectrum) was aimed at constructing an absorption spectrum starting at 380nm, from which the maximum absorption was determined and tabulated. In Lab Exercise #2 (Preparation of Standard Curve), the same solution was used, and the wavelength of Amax determined was set. The Absorbance was measured and recorded against the concentration, and a graph was plotted using excel. The concentration of the unknown values was determined from the data, and the molar extinction coefficient was calculated.













Introduction
An absorption spectrum is a spectrum in which a drop in radiation intensity at particular wavelengths indicative of an absorbing substance appears as a pattern of dark lines or bands. UV-V and electronic spectrum is another name for the absorption spectrum. According to Beer-Law, Lambert's sample path length and sample concentration are proportional to the light absorption for a given material.
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Materials and Methods
In the first experiment (Absorption spectrum), the mid-range of a colored solution's concentration was chosen. A 1cm diameter tube and a starting wavelength of 380nm in the variable mode absorbance values were read and recorded as A value in worksheet#1.
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Results of the experiment
Slope and two unknown samples were determined. In the first experiment, the Absorbance showed a rapid increase from 0.35 to a peak of 0.95, after which *******************************(Hidden info)
. In the second experiment, the intercept at Y-axis occurred at 0.24 in a linear plot. The tables and figures are attached below:
Results Tables and Graphs
Worksheet #1: Absorbance Spectrum readings
Wavelengths (nm) Absorbance Wavelengths (nm) Absorbance
380 0.35 590 0.01
390 0.57 600 0.01
400 0.81 610 0.01
410 0.95 620 0.01
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Figure 1 - Table of data for Absorption Spectrum (Worksheet 1)
Worksheet #2: Standard Curve Readings
Concentration Absorbance
1 0 0.24
2 50 0.48
3 100 0.71
4 150 0.95
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Figure 2 - Table of data for Standard Curve (Worksheet 2)

Figure 3 - Absorption spectrum plot 1

Figure 4 – Standard curve graph 1

Calculations
The concentration of unknown solutions (UK1 and UK 2)
Using Excel, Y410nm = 0.004X + 0.24 which is because m = 0.004
Y = Absorbance
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Molar extinction coefficient
The extinction coefficient measures how strongly a molecular species absorbs light at a given wavelength
E: extinction coefficient (liters/mole x cm)
A = Ecl this can be changed to E = A/cl
Where E is the extinction coefficient (liters/mole x cm)
A is an absorbance point
L is distance travelled by light through solution in cm. In this case, it is 1cm.
C is the Molar concentration that corresponds to "A."
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Discussion
The Amax values in our Lab #1 experiment were 0.95 at a wavelength of 410nm. This being K2Cr207, it forms an equation of A410 = 0.004X + 0.24 whereas a reference record shows an equation of A350 = 0.4875m - 0.0002.
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