[Simons2]

A rock sample containing Cu was chemically digested; the resulting solution was made up to 100 mL in a volumetric flask. 10 mL of this solution was treated with appropriate reagents to result in 20mL of colored solution. The absorbance of this solution was measured at 454 nm in a 1 cm cell. The resulting absorbance was 0.393. A blank carried through the same procedure gave an absorbance of 0.045. If molar absorptivity of the Cu-containing colored compound is 7900, what is the amount of Cu in the rock sample (in mg)?

I've used the equation of A=ecl to get C.0497M (.393=7900*c*.01m) , but I'm not sure what I can do with this.

[Hunter2]

Lambert-Beer law
A = eps.*c*d. The eps is your 7900. But what is missing is the unit. So we dont know the concetration in which unit it will be given and which unit for the thickness of the cuvette has to be use. Normal value should be 7900 mol^-1*cm^-1*l, but it can be also different. Second thing you have to substract the blank.

[Simons2]

Lambert-Beer law
A = eps.*c*d. The eps is your 7900. But what is missing is the unit. So we dont know the concetration in which unit it will be given and which unit for the thickness of the cuvette has to be use. Normal value should be 7900 mol^-1*cm^-1*l, but it can be also different. Second thing you have to substract the blank.

If I use the units you gave, all I would need to do was divide the concentration by the MM of Cu to get grams correct?