What happens to the absorbance of cobalt(II) chloride solution as the concentration of the solution increases?

Week 6 – Report Sheet

Beer’s Law

Name     Individual typed Submission
SEC Tues.                       Wed.                            Fri.

Activity I.

  1.  What happens to the absorbance of cobalt(II) chloride solution as the concentration of the solution increases? (3 points) Code: analysis, observations, numerical values
  • How are absorbance and transmission of cobalt(II) chloride related? (3 pts) Code: analysis, observations, numerical values
  • Use Beer’s law equation to determine the molar absorptivity (Ɛ) for cobalt(II) chloride . (3 pts) Code: general formula, substitution, significant figures, units

Activity II.

  • Did you measure the absorbance of the two solutions at the same wavelength? Explain. (3 points) Code: numerical value, analysis, observations
  • What is/are the color(s) from the light source used to measure the two solutions? Describe the relationship between the color from the light source, the solution color, and the absorbance for each measured solution. (3 pts) Code: descriptions, observations, analysis

Activity III.

  • Based on your , complete Table 3 (3 pts). Code: title, descriptions, numerical values, general formula, number substitutions, sig. figs. 

Table 3. ADD Title

Solution Concentration (Add Unit) Wavelength (Add unit) Cuvette pathlength (Add unit) Absorbance Transmittance (%)
Nickel(II) chloride          
Nickel(II) chloride          
Nickel(II) chloride          

Add descriptions

  • Describe the relationship between the width of the cuvette (pathlength) and absorbance of light for nickel(II) chloride solution (4 pts) Code: analysis, numerical values
  •  Use the Beer’s Law to explain the relationship between the pathlength and the absorbance of light. Does this relationship support your results?  (3 pts) Code: general formula, analysis
  • Why does the absorbance of a certain solution change upon changing the pathlength? (3 pts) Code: analysis

Activity IV.

  1. Based on your results, complete Table 4 and Explain how the color of potassium chromate solution is related to the obtained wavelength(s) (8 pts)? Code: title, descriptions, numerical values

Table 4. Data from simulation for potassium chromate solution measured at _______ nm

Solution # Concentration (Add Unit) Absorbance
1    
2    
3    
4    
5    

Add descriptions

  1. Based on your results, provide a graph of absorbance versus concentration. (8 pts) Code: scheme, title, descriptions, regression line equation, R2
  1. What are calibration curves used for? What do they tell us? Code: analysis (2 points)
  1. A sample of water is being analyzed for the amount of potassium chromate. A chemist used UV-Vis spectrophotometer to measure the absorbance of this aqueous sample. The data indicated that the sample has an absorbance of 0.25. Based on your graph, can you determine the concentration of potassium chromate in this water sample? If yes, solve for the concentration and show all your work.  If you are unable to determine the concentration, propose a way to modify your experiment. Explain. (4 points) Code: general formula, substitution, significant figures, units, analysis