absorbance of 0.467. A standard solution was put through appropriate dilutions to give the concentrations of iron given in the table below and the absorbance measured. Calculate the percentage of iron in the grass sample. marks] [12 [Fe]/(ppm) Abs 2 0.164 5 0.425 8 0.628 12 0.951 16 1.26 20 1.582

A water sample was analyzed for Fe content using the iron- phenanthroline method. The following data were obtained from the analysis: Reagent Blank Absorbance Absorbance (au) Reagent Blank Absorbance 0.003 Concentration of Stock Solution: 10 ppm Volume of Stock Solution (mL) Total Volume of Standard Solution Concentration of Standard Solution (ppm) Absorbance (au) (mL) 0.50 10.00 0.012 1.00 10.00 0.132 2.00 10.00 0.267 3.00 10.00 0.349 4.00 10.00 0.428 5.00 10.00 0.560 Volume of Unknown Solution Total Volume of Unknown Solution Trial Absorbance (au) (mL) (mL) 1 5.00 10.00 0.289 2 5.00 10.00 0.296 3 5.00 10.00 0.281 Determine the value of the slope (m), y-intercept (b), and the coefficient of determination (r²) A m = 0.1128; b = -4.0 x 10-5; r2 = 0.9880 B m = 0.1128; b = -4.0 x 10-5; r² = 0.9762 C) m = 0.1128; b = -3.0 x 10-³; r² = 0.9880 D m = 0.1128; b = -3.0 x 10-³; r² = 0.9762

4. The %Mn in steel can also be determined spectrophotometrically by oxidizing the manganese to the intensely colored permanganate, MnO4-. Standard solutions of permanganate gave the following absorbances (in a 1 cm cell): ABSORBANCE CONC. OF MnO4 (g/mL) 0.210 1.05 x 10-5 0.315 1.61 x 10-5 0.429 2.21 x 10-5 0.599 2.98 x 10-5 0.801 4.04 x 10-5 The following samples of steel were thoroughly reacted to convert the manganese into permanganate and then diluted to 500.00 mL. WT. OF STEEL (g) ABSORBANCE 0.5886 0.611 0.3498 0.359 0.4555 0.482 Again using Excel, plot the calibration data and calculate the %Mn in the steel.

A mined alloy sample weighing 2.0840 g is dissolved in minimal amounts of concentrated HNO3 before diluted to 50 mL. Ten mL of this diluted sample was titrated using 0.091 M KSCN and required 14.20 mL to reach the endpoint. Calculate the concentration of silver (%w/w) in the mined alloy. (Hint: A dilution factor (DF) is needed in the formula.) Titration reaction: Agt + SCN- → A9SC'N(s) FW: Ag = 107.87 %3D