Question

# An unknown amount of a compound with a molecular mass of 284.04 g/mol is dissolved in...

An unknown amount of a compound with a molecular mass of 284.04 g/mol is dissolved in a 10 mL volumetric flask. A 1.00 mL aliquot of this solution is transferred to a 25 mL volumetric flask, and enough water is added to dilute to the mark. The absorbance of this diluted solution at 347 nm is 0.472 in a 1.000 cm cuvet. The molar absorptivity for this compound at 347 nm is ?347=6023 M−1cm−1. What is the concentration of the compound in the cuvet? concentration: M What is the concentration of the compound in the 10 mL flask? concentration: M How many milligrams of compound were used to make the 10 mL solution? mass: mg

Here we find the concentration of the solution in the cuvette by using Beer-Lambert's Law. It states that the absorbance of the solution is directly proportional to the concentration of the solution. Mathematically expression of the above statement is

A α c

A = l c

where A is the absorbance of the solution

is the molar conductivity of the solution

l is the path length

c is the concentration of the solution

After finding the concentration of the solution in cuvette we find the concentration in the first volumetric flask using the relation

M1V1 = M2V2

The complete solution is shown in the images below:

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