Dilutions questions II - (Sep/04/2013 )

1.  Make 5 ml of .25 solution from 2.5 ml of a 1 M solution.

Why is 2.5ml not the initial volume.  Can you please explain.

I know the answer and the formula M1Vi=M2V2, but I want to know what concept I am missing.

2.  You have 5 ul of 1:60 Antibody +5 ul of buffer to make a ___________ dilution at ____________ ug/ul.

Antibody=600 ug/ul

The way I did it. 

1.  600 times 1/60=10 ug/ul

2.  I have 5 ul.  In 5 ul there is 50ug.  100ug/total volume=50ug/10ul=5 ug/ul

3.  5 ug/ul:600 ug/ul=1:120

My answer is correct, but I have a few questions.

Can we figure out the dilution first and how?

uzalive on Wed Sep 4 19:02:50 2013 said:

1.  Make 5 ml of .25 solution from 2.5 ml of a 1 M solution.

 

Why is 2.5ml not the initial volume.  Can you please explain.

I know the answer and the formula M1Vi=M2V2, but I want to know what concept I am missing.

 

 

 

2.  You have 5 ul of 1:60 Antibody +5 ul of buffer to make a ___________ dilution at ____________ ug/ul.

Antibody=600 ug/ul

The way I did it. 

1.  600 times 1/60=10 ug/ul

2.  I have 5 ul.  In 5 ul there is 50ug.  100ug/total volume=50ug/10ul=5 ug/ul

3.  5 ug/ul:600 ug/ul=1:120

 

My answer is correct, but I have a few questions.

 

Can we figure out the dilution first and how?

Second question:

If you have a 1:60 diluted sample in 5µl and you add 5 more µl, then what happened?

You diluted it again 1:2 ==> so total dilution is (1x1):(60x2)= 1:120

First question: I dont understand your question.

in question 1, if i understand you correctly, what you are missing is that you don't have to (in fact, you can't) use the whole 2.5 ml of 1.0M to make 5 ml of 0.25M (if you take 2.5 ml and dilute to 5 ml you will end up with 0.5M).