Sciencemadness Discussion Board

Dilutions in Chemistry

zinc1908 - 1-10-2009 at 16:59

What volume of .0250 M MgCl2 should be diluted to 250.0mL to obtain a solution with the [Cl] ion = .0135 M

Formula409 - 1-10-2009 at 17:20

Firstly I would post this in the Beginnings section.

Here goes:

So you have a .0250M MgCl2 solution. So you have 0.0250 moles of Mg and Cl2 (in a 1L soln).
This means that you have 0.05 moles of Cl- (again in a 1L soln).

So your solution is a 0.05M solution of the Cl- ion.

The moles in the original solution and the moles in the diluted solution will be equal.
n = n
But n = cv
So cv = cv
0.05*v = 0.0135 * .250
v = 0.0675L
v = 67.5mL

I hope that's right!

Pray tell you actually learn the method from this instead of me just doing your homework!

Formula409.

[Edited on 2-10-2009 by Formula409]

Magpie - 1-10-2009 at 17:30

molarity x volume = molarity x volume

2(0.0250)V = (0.0135)(250.0)