Posted by Lou on Friday, May 4, 2012 at 1:13am.
An aqueous solution of NaCl has a concentration of .500 M. 35.0 mL of this solution is allowed to evaporate to a volume of 20.0 mL.
a) Is the solution more concentrated or more dilute afterwards?
b) What is the new concentration of the solution?

Honors Chemistry  DrBob222, Friday, May 4, 2012 at 6:20pm
M = mols/L
a. If some solvent (L) has evaporated then L is a smaller number and M goes up and it is more concentrated.
b. new concn =
I would use 0.500M x (35/20) = ? BUT YOU may prefer to use the dilution formula.
c1v1 = c2v2
c = concentration
v = volume
35 mL x 0.500 = 20 mL x ?M
?M = 35*0.500/20 = ?