Preparing 5 dilutions of 0.200M NiSO4?

Question

I’m supposed to be preparing five dilutions from 50.0 mL of 0.200M NiSO4 stock solution. Instructions say that I will need standard solutions with five different concentrations and all standards must have absorbances above 0.1

. How do I go about this?

Answer 1

Without knowing the extinction coefficient and/or the wavelength, one can't really say which dilutions will have absorbance values > 0.1, but you can start as shown below, and then if the absorbance of any is <0.1 you'll have to change. Otherwise, if you know the extinction coefficient, supply that in a re-post, and maybe we can help.

0.200 M NiSO4 stock (50 ml)

(1) dilute 1:1 => 5 ml stock + 5 ml H2O = 0.100 M NiSO4 (10 ml)

(2) dilute stock 1:5 => 5 ml stock + 20 ml H2O = 0.04 M NiSO4 (25 ml)

(3) dilute stock 1:10 => 0.1 ml + 9.9 ml H2O = 0.02 M NiSO4 (10 ml)

(4) dilute stock 1:20 => 1 ml + 19 ml H2O = 0.01 M NiSO4 (20 ml)

(5) dilute stock 1:50 => 0.1 ml + 4.9 l H2O = 0.004 M NiSO4 (5 ml)

 

If you are required to use SERIAL dilutions, then all above dilutions should be ignored, when you re-post the question, be sure to state the you want to make SERIAL dilutions.  The problem with serial dilution is that if you make an error in one, that is transferred to all the following solutions. This is especially concerning if the error is made in the very first dilution.