uuestion 5 ol 8 En Sapling Learning Map An unknown amount of a compound with a m

Question

uuestion 5 ol 8 En Sapling Learning Map An unknown amount of a compound with a molecular mass of 270.08 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 325 nm is 0.516 in a 1.000- Cm cuvette. The molar absorptivity for this compound at 325 nm is E325 = 6531 M-cm-1. (a) What is the concentration of the compound in the cuvette? Number (b) What is the concentration of the compound in the 10-mL flask? Number C) How many milligrams of compound were used to make the 10-mL solution? Number mg O Previous @ Give Up & View Solution Q Check Answer O Next Exit

Explanation / Answer

the molecular formula = 270.08 g / mole

a) we will use beer lambert's law here

Absorbance = X c X l

l = length of cuvette = 1cm

= molar absrobptivity = 6531 M -1 cm-1

0.516 = concentration X 1 X 6531

concentration = 0.516 / 6531

concentration = 7.90 x 10^-5 M

b) concentration in 10mL will be

M1V1 = M2V2

M1 X 1 = 7.90 x 10^-5 X 25

concnetration = 1.98 x 10^-3 M

c) concentration = Mass of solute / molecular weight of solute X volume of solution

Mass of solute = 1.98 x 10^-3 X 270.08 X 10 mL

Mass of solute = 5.365 mg

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