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Question: A chemistry student wants to determine the concentration of copper (II) ions in a water sample. The student has access to a UV-Vis spectrophotometer and a copper (II) sulfate standard solution. Outline the steps the student should take to quantify the concentration of copper (II) ions in the water.

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ago by (450 points)
1. Prepare a series of standard solutions: The student should first prepare a series of standard solutions with known concentrations of copper  II  sulfate. This can be done by diluting the stock copper  II  sulfate solution to various concentrations, such as 1 ppm, 5 ppm, 10 ppm, 20 ppm, and 50 ppm.2. Measure the absorbance of the standard solutions: Using the UV-Vis spectrophotometer, the student should measure the absorbance of each standard solution at the wavelength where copper  II  ions have maximum absorbance  around 800 nm . Record the absorbance values for each standard solution.3. Plot a calibration curve: Using the absorbance values obtained in step 2, plot a calibration curve with absorbance on the y-axis and concentration on the x-axis. Fit a linear regression line to the data points, and determine the equation of the line  y = mx + b, where m is the slope and b is the y-intercept .4. Prepare the water sample: Filter the water sample to remove any suspended particles that may interfere with the absorbance measurements. If necessary, dilute the water sample to ensure that its copper  II  ion concentration falls within the range of the calibration curve.5. Measure the absorbance of the water sample: Using the UV-Vis spectrophotometer, measure the absorbance of the prepared water sample at the same wavelength used for the standard solutions  around 800 nm .6. Calculate the concentration of copper  II  ions in the water sample: Using the equation of the calibration curve obtained in step 3, substitute the absorbance value of the water sample  y  and solve for the concentration  x . This will give the concentration of copper  II  ions in the water sample.7. Adjust for dilution  if necessary : If the water sample was diluted in step 4, multiply the calculated concentration by the dilution factor to obtain the actual concentration of copper  II  ions in the original water sample.By following these steps, the student will be able to quantify the concentration of copper  II  ions in the water sample using a UV-Vis spectrophotometer and a copper  II  sulfate standard solution.

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