Question

a.If a solution of a compound that has a molar absorptivity 45 M–1 cm–1 placed in...

a.If a solution of a compound that has a molar absorptivity 45 M–1 cm–1 placed in a cuvette with a path length of 10 mm has an absorbance of 0.65, what is the molarity of the compound in solution? Show work.

b. What would the value of the equilibrium constant be for the formation of FeNCS2+ from Fe3+ and SCN– , if the final equilibrium concentration of [FeNCS2+] = 7.84 x 10–3 M when the solution initially had [Fe3+] = 1.5 x 10–3 M and [SCN– ] = 7.5 x 10–3 M?

c. Calculate the final [FeSCN2+] concentrations in flasks 1–6 from the Preparations of Calibration Curve procedure. Show work.

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Answer #1

a. The providing data in the question are as follow:-

Molar absorptivity () of a compound = 45 M-1cm-1

Path length (l) of a cuvette = 10 mm

= 1 cm [1 mm = 0.1 cm]

Absorbance (A) = 0.65

We need to find out the value of molarity (C) or concentration of the compound in solution -

We remember the formula,

A = cl

c = A / l

c = 0.65 / 45 M-1cm-1* 1cm

c = 0.0145 M

So, Molarity of the compound in solution = 0.0145 M

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