To Whom it May Concern, I am having trouble understanding how to apply certainva

Question

To Whom it May Concern, I am having trouble understanding how to apply certainvariables in this question. Also, the wording is confusing me themore I look at it. It goes like this: Question: A substance is known to have itswavelength of maximum absorption a molar extinction coefficient of 4,000 L.mol-1.cm-1. Suppose that a25.00 mL aliquot of an aqueous solution of this substance indiluted to a total volume of 100.0 mL. The absorption of thissolution in a 1 cm sample cell was found to be 0.950. Determine theconcentration of the original solution. Thoughts: 1) I assume that you would want to rewrite Beer's Lawas c=(A/b). 2) An aliquot is a portion of a total amount of asolution. 3) The path length of the sample, b, is 1 cm? 4) Where do the two values for volume come intoplay?    To Whom it May Concern, I am having trouble understanding how to apply certainvariables in this question. Also, the wording is confusing me themore I look at it. It goes like this: Question: A substance is known to have itswavelength of maximum absorption a molar extinction coefficient of 4,000 L.mol-1.cm-1. Suppose that a25.00 mL aliquot of an aqueous solution of this substance indiluted to a total volume of 100.0 mL. The absorption of thissolution in a 1 cm sample cell was found to be 0.950. Determine theconcentration of the original solution. Thoughts: 1) I assume that you would want to rewrite Beer's Lawas c=(A/b). 2) An aliquot is a portion of a total amount of asolution. 3) The path length of the sample, b, is 1 cm? 4) Where do the two values for volume come intoplay?   

Explanation / Answer

You have c = (A/eb). Plugging the values you have intothe equation you get c = (0.950/(4000 Lmol-1cm-1*1cm)). c = 0.0002375 mol/L = 0.0002375 M So, you now have the concentration of the dilutedsolution. Next, useM1V1=M2V2 to determinethe concentration of the original solution. M1(25.00 mL) = (0.0002375 M)(100.0 mL) M1 = 0.00094 M

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