Homework SourseTo Whom it May Concern I am having trouble understanding how
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?
Solution
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
