Question

Questions 1. Consider the calibration graph and the absorption spectrum for solutions of metal ion, M * Absorption Spectrum for M Calibration Curve for M 0.8 0.7 1.2 0.6 1 0.5 S 0.8 0.4 0.6 0.3 0.4 0.2 0.1 0.2 0- 0 0.5 0.4 0.3 0.2 0.1 400 450 500 550 600 650 700 [M*1 (Molar) (入) nm a) At what wavelength was the calibration curve obtained? Explain your answer. b) Use the calibration curve to calculate the concentration (M) of the M solution with an absorbance of 0.630. Show your work. c) If 3.00 mL of a concentrated M solution was diluted with water to make 15.00 mL of the solution in b), calculate the concentration of the original concentrated M solution. Show your work Absorption Absorption Purple Blue MO e6ueJo peH

Answer 1

Answer 1 a) The calibration curve is obtained by using wavelength at which metal ion absorbs to maximum extent.In absorption spectrum as shown in figure, metal ion absorbs o maximum extent around 425nm ( Purple region). Hence absorption is recorded using wavelength around 425nm.

b) To find the concentration of solution with an absorbance 0.630, a line is drawn(Orange line) as shown in figure. It corresponds to 0.35M (x-axis)

Calibration Curve for M 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.1 02 03 04 0.5 M)(Molar) Absorption

Answer c) M₁ V₁ = M₂V₂   

M_{1 =}  M₂ (from graph) x V₂ / V₁

M_{1 =}  M₂ (from graph) x V₂ / V₁

= 0.35 x 15 / 3

= 1.75 M