Potassium dichromate and potassium permanganat
问题详情
Potassium dichromate and potassium permanganate have over lapping absorption spectra in 1mol·L-1 H2SO4. K2Cr2O7 has an absorption maximum at 440nm，and KMnO4 has a band at 545nm. A mixture is analyzed by measuring the absorbance at these two wavelengths with the following result：A440=0.405，A545=0.712 in a 1.00cm cell(approximate；exact length not known). The absorbances of pure solution of K2Cr2O7(1.00×10-3mol·L-1)and KMnO4(2.00×10-4mol·L-1)in 1mol·L-1 H2SO4，using the same cell gave the following resuits；
ACr,440=0.374，ACr,545=0.009，AMn,440=0.019，AMn,545=0.475. Calculate the concentrations of dichromate and permanganate in the sample solution.
参考答案
Since A=kbc
0.374=kCr,440×1.00cm×1.00×10-3mol·L-1 kCr,440＝374L·mol-1·cm-1
0.009=kCr,545×1.00cm×1.00×10-3mol·L-1 kCr,545＝9.00L·mol-1·cm-1
0.019=kMn,440×1.00cm×2.00×10-4mol·L-1 kMn,440＝95.0L·mol-1·cm-1
0.475=kMn,545×1.00cm×2.00×10-4mol·L-1 kMn,545＝2380L·mol-1·cm-1
and
