14-12 The method developed in Problem 14-11 was used for the routine determination of iron in 25.0-mL aliquots of groundwater. Express the concentration (as ppm Fe) in samples that yielded the accompanying absorbance data (1.00-cm cell). Calculate the relative standard deviation of the result. Repeat the calculation assuming the absorbance data are means of three measurements. (a) 0.143 (b) 0.675 (c) 0.068 (e) 1.512 (d) 1.009 (f) 0.546