Monday, March 28, 2011

LESSON 27 DILUTION

Diluting Solutions
  • when 2 solutions are mixed the concentrations changes
  • dilution is process of decreasing the concentration by adding a solvent(usually water)
  • the amount of solute doesn't change
    •  nB   =   nA       (n = the # of moles)         (B - before ,  A - after)
  • since concentration is mol/L you can write:
    • C = n/v
    • n = CV
    • C1V1  =  C2V2
eg. A 45.0 mL of 12.1 M of HCl is diluted to a final volume of 250mL. What is the concentration 
      of the new solution?
C1V1 = C2V2
1. (12.1M)(0.045L)  =  C2 (.250L)

2. (12.1)(0.045L)  =  C2 (.250)     -->   C2 = 2.18 mol/L
           .250                   .250 

eg. 150 mL of 0.266 M  2NaSO4 is added to 525 mL of 0.135 M 2NaSO4. What is the [2NaSO4].

(.150 L  x  0.266 mol)  =  0.0399  mol
                         L           +
(.525 L  x  0.135 mol)  =  0.07087 mol
                         L              0. 1108  mol

 [2NaSO4]  -->   0.1108 mol   =  0.16 M
                             .675 L

(150ml+525ml = 675ml)

eg. H2CO3 has a concentration of 16.5 M. How much concentrated do you need to make 2.00 L of 2.00M H2CO3? 
C1V1 = C2V2

(16.5)V1 =  (2.00)(2.00)    --->   V1 = 0.242 L
   16.5              16.5
 -sherilyn





posted by chemistry11 @ 11:20 PM

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