# Copper Sulphate Calibration

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Copper Sulphate Calibration
Copper Sulphate Calibration
Aim
The objective of this experiment is to determine the unknown concentrations of solutions.
Introduction
With the use of absorption of light a spectrophotometer sends UV wavelengths through solutions to determine their concentrations. The light absorbed is measured as the atoms, molecules and ions absorb the wavelengths of light that the spectrophotometer gives off (Meah,2013). The level of light transmitted defines the amount of light absorbed, for instance, the lower the light absorbance the higher the amount of light transmitted. Ultraviolet (UV) light is radiation but the wavelength is shorter than visible light.
A solution is a mixture of two or more substances. A stock solution is used to make a variety of other solutions which hold different concentrations; this is done via dilutions (Meah, 2013). Diluting a solution means dispersing an amount of solute over a bigger solution. A standard solution has a known concentration and it is prepared from a stock solution which has a fixed volume and has been weighed. Having a standard solution is essential as it will be easy when finding the unknown concentrations as it allows for better comparison between the two.
Method
As per laboratory protocol.
Results and Discussion
From the table and graph it shows that there is a linear relationship between concentration and absorption (Beer-Lambert Law). As the concentration increases so does the absorbance. The line of regression fits into the averages of the UV Absorbance, the R2 is 0.9538 this shows that the data is accurate as it is very close to the regression line. Taking the averages of the UV Absorbance allows the data to become more accurate and reliable.
Cuvette
1M CuSO4 (mL)
Distilled Water (mL)
Concentration (M)
UV Absorbance (Average)
1
2
8
0.2
0.566
2
4
6
0.4
0.955
3
6
4
0.6
1.243
4
8
2
0.8
1.539
5
10
0
1
1.995

Dividing the unknown solutions by y is the way to find the concentrations of the unknown solutions. Plotting the

References: Determining the Concentration of Copper Sulphate available from http://www.westminster.edu/acad/sim/pdf/SDETERMININGTHECONCENTRATIONOFACOPPER.pdf [25th November 2014] Meah, M, and Kebede-Westhead, E (2013) ‘Spectrophotometer’ in Essential Laboratory Skills for Biosciences. 60-61 Introduction of UV radiation and UV index available from http://www.hko.gov.hk/wxinfo/uvindex/english/whatisuv.htm [25th November 2014] Meah, M, and Kebede-Westhead, E (2013) ‘Solutions’ in Essential Laboratory Skills for Biosciences. 22 Standard Solution available from http://www.chem-ilp.net/labTechniques/StandardSolutions.htm [25th November 2014] Spectronic 20D+ Spectrophotometer available from http://umdearborn.edu/casl/fileadmin/casl/departments/naturalsciences/PDFS/Spec20D__new_module.pdf [26th November 2014] Beer-Lambert Law available from https://hplc.chem.shu.edu/NEW/Undergrad/Molec_Spectr/Lambert.html [28th November 2014]

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