To find the concentration of the complex [Fe(SCN)]^2+, each solution is measured

Question

To find the concentration of the complex [Fe(SCN)]^2+, each solution is measured with the same spectrophotometer at the appropriate wavelength, while careful attention is being paid to the blankin process.

Vial# 1
Absorbance = 0.302

Vial# 2
Absorbance = 0.368

Vial# 3
Absorbance = 0.383

Vial# 4
Absorbance = 0.345

Vial# 5
Absorbance = 0.267

I was not sure if the path length and molar absorptivity were constant because nothing was given in my example but on another example the molar absorptivity was 4234 and the path length is 1.445

Explanation / Answer

KSCN + Fe(NO3)3 + HNO3 --> Fe(SCN) 2+... Fe 3+ + SCN- --> Fe(SCN) 2+ = net ionic equation moles Fe(NO3)3 = moles KSCN used A: 0.005L x 0.015M = 7.5x10^-5moles KSCN, 0.005L x 0.25M = 1.25x10^-3moles Fe(NO3)3 1.25x10^-3moles Fe 3+ + 7.5x10^-5moles SCN- --> 7.5x10^-5moles Fe(SCN) 2+ 7.5x10^-5moles Fe(SCN) 2+ / 0.015L = 0.005M Fe(SCN) 2+ B. 0.003L x 0.015M = 4.5x10^-5moles KSCN, 0.005L x 0.25M = 1.25x10^-3moles Fe(NO3)3, 4.5x10^-5moles SCN + 1.25x10^-3moles Fe 2+ --> 4.5x10^-5moles Fe(SCN) 2+ 4.5x10^-5moles Fe(SCN) 2+ / 0.015L = 0.003M Fe(SCN) 2+

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