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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: fatghost13 on August 08, 2013, 10:52:14 AM

Title: concentration problem
Post by: fatghost13 on August 08, 2013, 10:52:14 AM

The amount of chromium in a solution is to be determined by atomic absorption spectroscopy.
It is found that when 10.0 cm^3 of the unknown is diluted to 50.0 cm^3 the absorbance is measured as 0.201. A unknown sample of 10.0 cm3 is then added to 30.0 cm^3 of a solution containing 18.7 mg dm^3- of chromium and the mixture diluted to 50.0 cm^3; the absorbance of the second solution is found to be 0.603.
Given that the absorbance of the test solution is directly proportional to the concentration of the analyte, calculate the concentration of the unknown chromium solution.

As  absorbance  proportional to the concentration A1/A2=C1/C2 , A1=0.201 A2=0.603 ,
how can i find C1 and C2 ?

Title: Re: concentration problem
Post by: Hunter2 on August 09, 2013, 01:10:27 AM

You will have two equations.  A1 = k*C  and A2 = k*(add+C) Start with this