[Sis290025]

A solution is prepared by dissolving 171 g of CdCl2 in enough water to make 250.0 mL of solution. If the density of the solution is 1.556 g/mL, what is the molarity of the solution?
 
 
a.0.440 M  
 
b.3.73 M  
 
c.0.933 M  
 
d.0.684 M  


Molarity = (mol solute)/(L solution)

Now my key question of this problem is about the given density. How do you use it (if you do use it)?

Normally, I would do so:

171 g CdCl2 * (1 mol CdCl2/183.311 g CdCl2) = 0.9328409 mol CdCl2

It is given that the solution volume = 250 mL = 0.250 L.

M = 0.9328409 mol CdCl2/0.250 L = 3.73 M

But the density is confusing me.

Please help soon.

Thank you.

[Alberto_Kravina]

You don't need the density to calculate the molarity in this case!

c=n/V

n=m/M = 0.9328409 mol

V=0.25L

c=0.9328409 mol / 0.25L = 3.73 mol/L