Question

25.0 ml C solution is diluted to 50.0 ml and the absorbance is 0.416 in 348...

25.0 ml C solution is diluted to 50.0 ml and the absorbance is 0.416 in 348 nm in a 1.00-cm cuvette. 25.0 ml second solution is added 10.0 ml solution that contains 23.4 ppm of C. After diluted to 50.0 ml this solution has absorbance 0.610 in the same cuvette and wavelength. Calculate concentration (ppm) C in sample.

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Homework Answers

Answer #1

20.08ppm

Explanation

Cx/(Cx + Ca) = Sx/Sx+a

Cx = unknown concentration

Ca = added concentration

Sx = unkown signal

Sx+a= signal for unknown + added concencentration

put , Cx = x

Ca = 4.68ppm ( 10ml of 23.4 ppm solution C is dilduted to 50ml , so final added Concentration is 23.4/5 = 4.68ppm)

x/(x + 4.68 ppm) = 0.416/0.610

x/(x + 4.68ppm) =0.6820

x = 0.6820x + 3.192ppm

0.318x = 3.192ppm

x = 10.04ppm

unknown concentration in 50ml solution = 10.04ppm

Dilution factor = 50/25 = 2

Concentration in sample = 10.02ppm × 2 = 20.08ppm

     

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