• Support PF! Buy your school textbooks, materials and every day products Here!

Dilutions question

  • Thread starter FuturePA
  • Start date
  • #1
2
0

Homework Statement


To what volume shuould you dilute 125 mL of an 8.00 mL CuCl2 solution so that 50.0 mL of the diluted solution contains 5.9 g CuCl2?


Homework Equations



M= mol solute / vol solution (L)
m = mol solute / mass solvent (kg)
mole percent = mol solute / mol solute + solvent


The Attempt at a Solution


8.00 M = mol CuCl2 / .125 L
1 mol CuCl2 x (65.55 + 2(35.45)g / 1 mol CuCl2 = 134.45 g CuCl2
5.9 g CuCl2 (final) x (1 mol CuCl2) / (65.55 +2(35.45)g = .4388 mol CuCl2
8.00 M = .44 mol CuCl2 --> .055 L solution???????????
I don't know how to use these formulas to find the diluted amount using the old amount? Do I subtract the grams CuCl2 to the new Molarity and find the tot vol? The answer is not the same as the back of the book.
THANKS SO MUCH!
 

Answers and Replies

  • #2
Borek
Mentor
28,326
2,710
How many moles of CuCl2 do you have?

What molarity do you need?

C=n/V
 
  • #3
2
0
Vapor Pressure Problem

An aq CaCl2 colution has a vapor pressure of 81.6 mmHg at 50 degrees C. The vapor pressure of pure water at this temperature is 92.6 mmHg. What is the concentration of CaCl2 in mass percent?

I don't even know where to start, if I can use Raoult's Law or not . . .
 
  • #4
Borek
Mentor
28,326
2,710
You can. Just assume that whatever is dissolved has a vapor pressure of zero.
 
  • #5
The question doesnt even make any sense.

you have 0.125dm3 of 8 molar CuCl2 and you want to turn it into 0.050dm3 of CuCl2?
 
  • #6
is the answer 9.09m3?

im guessing its a typo and you have 8 molar CuCl2 you need to dilute it so that 0.050dm3 has 0.044moles.

divide 8 moles with 0.044 and you get 181.81 then divide that with 0.050.
 

Related Threads for: Dilutions question

  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
811
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
3
Views
5K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
14
Views
621
Top