# Homework Help: Absorbance of diluted solution

1. Apr 23, 2010

### hongkong

Solution A, while in a 1.0 cm cell, has an absorbance of 0.390 and a [Cu2+] = 0.0283 M. Then, 6.57 mL of solution A is diluted with pure water to 100.0 mL. What is the absorbance of this diluted solution?

The below is what I did. But I am not sure about the answer. Can you please check it? If there is something wrong, please correct! Thanks a lot!

concentration of dilute solution----6.57ml of 0.0283M = 100.0ml x M
Solve for M----( 100 x 0.0283 ) / 6.57 = 0.4307

Solve for absorbance: 0.390/A = 0.0283/0.4307

==> Absorbance (A) = 5.93607

2. Apr 29, 2010

### chemisttree

Do you really believe that when you dilute something with an original absorbance of about 0.4 you get a solution with an absorbance of about 6?

Remember A = abc where a is molar absorptivity, b is path length and c is concentration. You can solve for 'a' using nothing more than what is originally given to you for Solution A. Use it to solve for the new 'c' in the diluted sample. 'a' will be the same for this compound regardless of its concentration.