1. The absorbance or percent transmittance measurements should be made at 410 nm. If other chemical species in the analytical solution absorb at 410 nm, then 575 nm would be a suitable wavelength.
   
   



2. The percent transmittance and absorbance measurements made at 410 nm are listed below.
   
   

   Standard Cr(III) Solutions	%T	A
   0.0100 M	66.0	0.180
   0.0200 M	43.7	0.360
   0.0300 M	29.3	0.532
   0.0400 M	20.2	0.694

   
   
   
3. A calibration curve was constructed with the aid of the Linear Regression applet. The plot of absorbances (y = A) versus the molarities of the standard Cr(H₂O)₆³⁺ solutions ( x = c = [Cr(III)] ) is a straight line. The Cr(H₂O)₆³⁺ solutions comply with Beer's law.
   
   
   
   



4. 
   
   





5. The percent transmittance and absorbance of unknown #1 were measured at 410 nm and are listed below.
   
   

   Unknown	%T	A
   #1	23.1	0.637

   
   
   Note that the intercept for the plot of A versus [ Cr(H₂O)₆³⁺] is not zero.