I have worked through the problem a multitude of times, and am unable to get the right answer. Any help would be appreciated. Thanks.
Cu does not absorb strongly in the visible, but a colored product containing only 1 mole Cu/mol product does. A series of Cu standards was prepared by mixing color developing reagents with different volumes of a stock Cu standard to form the product before diluting to volume in volumetric flasks. In a 3-cm cell, a graph of absorbance, A, vs concentration of Cu in µg Cu/mL gave a straight line calibration curve. The data were fit to a straight line:
A = a b C + Ablank
A = E*b*C, e= molecular absorption, b= cell size, and c = concentration.
The results of the Excel linest function are given below.
0.5707 -0.0760
0.001382 0.0433
0.99376 0.01810
x 7
x x
1) Calculate the 95 % confidence limit in the absorbance of the blank.
2) Calculate the molar absorptivity of the product in cm2/mmol Cu. a. w. Cu = 63.5