Dilution and Preparing solutions
Standard solution – a solution with a known concentration.
2 Ways to make standard solutions:
1)
Dissolve a known mass of solute in a certain volume of solution.
2)
Dilute a solution of known concentration.
Dilution – procedure for preparing less concentrated solutions from concentrated ones.
Eg. How would you prepare a 1L sample of 0.400 M KMnO4 solution from a solution of 1.00 M KMnO4?
C = n/V
or n = C x V = 0.4 M x 1L = 0.4 mol
 0.4 mol of KMnO4 is needed.
Find volume of stock solution:
CiVi = CfVf
C = n/V or
NOTICE:
V = n/C = 0.4 mol/1.0 M =0.4 L
Ci Vi = n
and
n = CfVf
(The Dilution Equation)
***DO NOT USE THIS FOR ANYTHING OTHER THAN A DILUTION SCENARIO!!!***
E.g. You want to prepare 500 mL of 1.75 M solution of H2SO4 from 8.61 M of H2SO4 stock solution.
What volume of the stock solution must you dilute?
Ci = 8.61 M
Vi = ?
Cf =1.75 M
VF = 500 mL = 0.5 L
CiVi = CfVf
Vi = CfVf
Ci
=
1.75 M x 0.5 L
8.61 M
=
Volume of water to be added
= 500 mL – 102 mL = 398 mL
0.102 L
p. 386 #51-60
p. 388 #13-18
p. 390 #1-14
p. 399 #1-39
p. 402 #1-28