# rxn problem, for the reawakening brain =)

Eric Wilk Eric.Wilk at tufts.edu
Sun Jul 6 18:37:04 EST 2003

```waym at ohsu.edu wrote in message news:<20030630224507.32686.qmail at ww02.hostica.com>...
> 1. Rxn: 10 uL, 100 mM NaCl
> then
> 2. Rxn: add 1 uL enyme, X uL H20, Y uL 5 M NaCl to final volume of 150 mM.
>
> What is X = ?
> What is Y = ?
>
> http://biowww.net/mynews/tree.php?group_name=bionet_molbio_methds-reagnts&begin=0

I got .134 ul of 5 M NaCl to make a total volume of 11.134 ul.  Don't
know why you'd need to add extra water, unless you don't want to
measure .134 ul.  In this case, decrease the molarity of the NaCl and
use this algebraic model using liters and moles as units only (i am
starting with an assumed .000011 L and .000001 mol and X is the volume
of NaCl to be added :

Total molarity = .000001 mol + (molarity of salt solution)X

Total volume = .000011 + X

(Total molarity)/(Total Volume) = .15 mol/L

Solve for X

(This was assuming no salt in the enzyme solution.)

Cheers!

-- Eric

```