Fe3+(aq) + KSCN(s) → FeSCN2+(aq) + K+(aq) To determine the…
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Fe3+(аq) + KSCN(s) → FeSCN2+(аq) + K+(аq) Tо determine the mоles оf Fe3+(aq) in a 100. mL sample of an unknown solution, excess KSCN(s) is added to convert all the Fe3+(aq) into the dark red species FeSCN2+(aq), as represented by the equation above. The absorbance of FeSCN2+(aq) at different concentrations is shown in the graph below. The figure presents the graph in the first quadrant of a coordinate plane. The horizontal axis is labeled “Concentration of F e S C N with a positive 2 charge, in Molar,” and the following three numbers are indicated: 0, 5 times 10 to the negative 5, and 10 times 10 to the negative 5, in increments of 1 times 10 to the negative 5. The vertical axis is labeled “Absorbance at 453 nanometers,” and the numbers 0 through 0 points 5 0, in increments of 0 point 1 0, are indicated. The line of best fit is drawn. The line begins where the axes meet. It moves steadily upward and to the right passing through the point 5 times 10 to the negative 5 Molar and 0 point 2 5 absorbance. The line ends at 10 times 10 to the negative 5 Molar and 0 point 5 0 absorbance. There are 6 data points along the line. 1 point is at the origin, 3 points are above the line, and 2 points are below. If the absorbance of the mixture is 0.20 at 453 nm, how many moles of Fe3+(aq) were present in the 100. mL sample? (Assume that any volume change due to adding the KSCN(s) is negligible.)
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