# solution problem - (Jun/06/2006 )

Can someone please show me how to do this problem? I keep getting the wrong answer. For the problem, Substance X is a dye and in this case, it is added into water.

I have 1 mM of Substance X. It was given to us at 500ul, but after usage, this volume lowered. I don't have the current volume; it is lower than 500ul, but it's not 0 ul. I must make my own Substance X with a concentration of 50uM and 50ul final volume. How much of the Substance X do I pull up and add into the water?

Concen 1 = 1 mM
Vol 1 = x
Concen 2 = 50 uM
Vol 2 = final volume of 50ul total

1 mM = 1 mmol/ml = 0.001 mmol/ul

C1*V1 = C2*V2

How do I do this problem?? Please help! All I need to know is how much of Substance X dye do I pull up from the stock tube and add into the new test tube. I will raise the rest up with water to a final volume of 50ul. Thanks.

-ck111-

QUOTE (ck111 @ Jun 6 2006, 07:49 AM)
C1*V1 = C2*V2

N1*V1 = N2*V2

consider N= C/M

-akhshik-

not sure if i have misread or not, but it seems like you want to dilute something to a higher concentration!!!!
unfortunately you can't take some of this solution and then add water to give a concentration that is higher than your starting conc.....
so, you have 1mM and want 50mM?
do you mean 1M or 100mM?
sorry....

-aussieuk-

QUOTE (aussieuk @ Jun 6 2006, 11:36 AM)
not sure if i have misread or not, but it seems like you want to dilute something to a higher concentration!!!!
unfortunately you can't take some of this solution and then add water to give a concentration that is higher than your starting conc.....
so, you have 1mM and want 50mM?
do you mean 1M or 100mM?
sorry....

Oops, it is 50uM. I have changed the orig. post.

-ck111-

Youa re making a mistake with your units. The final concentration is 50uM...

To make it easier it is 1/20th of 1mM, so what you need is to dilute 20 times.

-Canalon-

1mM=1000uM
therefore your units need to be the same either both (mM) or (uM)

C1V1=C2V2
(1000uM)(V1)=(50uM)(50ul)
V1=2.5ul dye and top up to 50ul with water

or as stated above 1/20th of your final dilution

-grapes of wrath-