I have a couple questions (1) A sample containing 0.0250 M concentration of a dy

Question

I have a couple questions (1) A sample containing 0.0250 M concentration of a dye in a cell of 1 cm2 cross section has a measured absorbance of 1.012 at 650 nm. Calculate the instrumental constant "k" for the spectrophotometer at that wavelength. (2) A sample of the same dye in the same cell and spectrophotometer has a measured absorbance of 0.672 at the same wavelength. Calculate the dye concentration. (3) 5.00 mL of 0.00500 M ferric nitrate is added to 5.00 mL of nitric acid and 10.0 mL of 0.00250 M thiocyanate solution. Calculate the initial Fe3+ concentration before reaction.

Explanation / Answer

1)

A = E*C*L ..

where E=instrumental constant

A=absorbance

L=length

E=A/C*L=1.012/(0.0250*650*10^-9) = 6.22*10^7

2)

A=0.672

so,

C=A/E*L =0.672/(6.22*10^7*650*10^-9)=0.016 M

3)

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