After the addition the solutions are diluted to mark and then covered with

# After the addition the solutions are diluted to mark

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After the addition, the solutions are diluted to mark and then covered with parafilm. The solutions were then subjected to the Uv-Vis spectrophotometer. The

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analytical wavelength or the wavelength where the absorbance of the solution is at its peak was first determined. The most concentrated solution was used to maximize the absorbing capacity of the solution, which is solution 6 for this experiment. Solution 6 was poured in the cell and the instrument was turned to spectrum mode. The wavelength range was set to 300nm to 700nm, the visible light range. The instrument scanned and the analytical wavelength was determined, this would be used for the absorbance reading of the other solutions since this is where absorbance is maximized and error possibility is at its lowest. The next step was to eliminate the effect of ammonia to the absorbance of the solution, in order to do this, solution 1 or the blank solution in the cuvette was scanned and the value was put to autozero. The absorbance of solutions 1-6 was then determined. The order is from the lowest to the highest copper (II) content to minimize concentration increase for each analyte. Lastly is the determination of the sample’s absorbance, which was done in triplicate. RESULTS AND DISCUSSION The analytical wavelength is 596 nm. This means the solution is the hue of blue-green. This is the monochromatic light that was used in the experiment (Jeffrey, 660). In the introduction, the concepts of spectrophotometry were discussed; it was then used to collect the needed data for the graph of the best-fit line and its equation. 50 100150200250300350400450500550 0 0.1 0.2 0.3 0.4 0.5 f(x) = 0 x − 0.01 R² = 1 Concentration A b s o r b a n c e Figure 3. Relationship of absorbance of Cu 2+ solutions to their corresponding concentrations As conferred before, the absorbance of an analyte is proportional to its concentration. Absorbance values from the copper solutions with known concentrations are collected and graphed vs. each parts per million or ppm of a solution, a trend line and a corresponding equation were determined. The equation was then used to determine the concentrations of copper solutions with known absorbance, x would be the value of concentration and y would be the absorbance. The equation for the relationship of the absorbance and concentration of the Cu 2+ solution is derived to be: y = 0.001 x – 0.005 ( 7 ) Concentration used absorbance instead of transmittance in quantification due to convenience with the linear relationship between A and c. This is the reason why the Beer’s Law is expressed in terms of absorbance rather than the transmittance. Since there is already a working equation, the concentration of the working sample solution and the initial analyte solution was calculated. Table 2. Sample Analysis Trial Absorban ce Cu 2+ ppm in Workin g Cu 2+ ppm in Initial Sampl
Sample e 1 0.386 381 ppm 2574 ppm 2 0.386 381 ppm 2574 ppm 3 0.386 381 ppm 2574 ppm Averag e 0.386 381 ppm 2574 ppm RSD 0 0 0 CI 0.386 381 ppm 2574 ppm Volume 50 mL 7.4 mL Percen t error 2.96% Table 1 shows the calculated data from the analysis of the sample copper solution. The concentrations and

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