The concept of spectroscopy has been applied in various fields especially after the advancement in science and technology. Apparently, the unique absorption wavelength of compounds or metals is fundamental in this experiment. Therefore, scientists can indemnify metals using absorbance of light intensity property. On the other hand, the flame test was also conducted in this experiment where the suggestions of the type of elements contained in the unknown were determined. There was an error of 1.0163% obtained in the experiment which can be associated with the approximations used during the reading and calculation of absorbance values.
Introduction
Researchers and scientists agree that the study of the interaction between electromagnetic radiation and matter is referred to as spectroscopy (Blauch). It should be noted that different elements display different colors when investigated using a spectrometer. The proponents of spectroscopy advanced their concepts from the study of dispersion of wavelengths of visible light through a prism ("Spectrophotometry"). In the bid to determine the element present, a spectrophotometer is used. This is a special device that is used to measure the absorbance or the intensity when a beam of light is passed through a solution. In this regard, the concentration of substance can be determined.
Figure 1: Spectrum of visible light through a glass prism
There are several laws or principles that can be applied in understanding the relationship between concentration and absorbance. One of these laws is the Beer-Lambert law; however, this law can only be applicable when there exist a linear relationship between the variable in the sample ("Spectrophotometry").
This experiment was divided into two sections; the first section entailed testing six types of metal using flame test while the second part entailed determination of the concentration of the solution by absorbance from the spectrophotometer. The primary aim of this experiment was to observe electromagnetic wave emission, construction of standard curves and be familiar with spectrophotometer.
Data
Section 1
Section 2
Solution Number
1
2
3
4
5
6
7
8
Absorbance
1.057
0.857
0.563
0.379
0.176
0.083
0.025
0.014
Table 2: Table of absorbance
Results and Discussion
In light of past research, the data in Table 1 conforms to the data available in literature for the chloride flames. The orange flame from the blank loop may be due to calcium chloride or copper (ii) sulphate. On the other hand, the unknown that depicts the red color may be attributed to calcium chloride.
In the bid to determine the concentrations of the solutions used to obtain the above absorbance we use the formula,
Therefore, concentration for the solution numbers,
A graph of concentration against absorbance
From the graph above it is evident that there is a positive linear relationship between concentration and the absorbance (Atkins and Julio 187). In this regard, the Beer-Lambert law can be applied. The dependent variable is taken as concentration and absorbance as the independent variable. From the linear regression line in the graph above, the concentration of the unknown is obtained as follows.
Therefore, the absorbance of 0.313 was obtained from a solution whose concentration was 0.6581. To calculate the percentage error in the experiment, the average of the absorbance is used.
% error =
% error =
Conclusion
From the data obtained in this experiment, the change in concentration directly affects the absorbance. Therefore, when the concentration is high, there are more molecules in the solution which increases the absorbance of the light through the spectrophotometer. This is in conjunction to Beer-Lamberts law.
Works Cited
Atkins, Peter, and Julio De Paula. Physical chemistry for the life sciences. Oxford University Press, USA, 2011.
Blauch, David N. "Spectrophotometry: Basic Principles." Davidson College Chemistry Resources, www.chm.davidson.edu/vce/spectrophotometry/Spectrophotometry.html.
"Spectrophotometry." Chemistry LibreTexts, 21 July 2016, chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Reaction_Rates/Experimental_Determination_of_Kinetcs/Spectrophotometry.
