Beer’s Law
   A student is instructed to determine the concentration is a 
   solution of CoCl2 based on the absorption of light. 
   (spectrophotometer/colorimeter method).The student is 
   provided with a 0.10M CoCl2 solution with which they are to 
   prepare standard solutions with concentrations of 0.020M, 
   0.040M, 0.060M and 0.080M.
   Describe the procedure for diluting the 0.10M solution to a 
   concentration of 0.020M using distilled water, a 100ml 
   volumetric flask, and a pipet or buret. Include Specific 
   amounts where appropriate.
     Solution: 1pt for CoCl ; 1 pt for H O
                                       2                 2
     MV = MV             
       1 1    2 2
     0.10M(V1) = 0.02M(100ml)
     V1 = 20ml CoCl2        80ml = H2O
     Pipet 20ml of the CoCl2 into a volumetric flask. Add enough 
     distilled water to the flask to reach the 100ml marking on 
     the flask. Mix well.
  Part b.
  A student takes the 0.10M solution and determines the 
  percent transmittance and the absorbance at various 
  wavelengths. The two graphs below represent the data:
  b. Identify the optimum wavelength for the analysis.
  Solution – 1 point:  The optimum wavelength is in the range 
  of 490 – 520nm. The actual wavelength is 510nm
   Part c
   The student measure the absorbance of the 0.020M, 0.040M, 0.060M, 
   0.080M and 0.10M solutions. The data are plotted below.
   c. The absorbance of the unknown solution is 0.275. What is the 
   concentration of the solution?
   Solution – 1 point: The acceptable range is 0.045M – 0.055M. The 
   actual value is 0.050M.
  d. Beer’s Law is an expression that includes three factors 
  that determine the amount of light that passes through a 
  solution. Identify two of these factors. 
  Solution: 1 point each factor ID’d and explained
  A=abc
  a=molar absorbtivity
  b=path length of the cuvette
  c=concentration