1. 9.2 Solution Stoichiometry
Learning Goals …
… determine the concentration of ions in a solution
… use Stoichiometry to find the minimum volume required to precipitate an ion
… use Stoichiometry to find the mass of a precipitate when two aqueous solutions are mixed

2. CONCENTRATION OF IONS
Ex. If the following solutions are mixed together, calculate the concentration of Mg2+, Cl-, and S2- in the mixture.
100 mL of 0.50 mol/L Magnesium chloride
200 mL of 0.75 mol/L Magnesium sulfide
100 mL of water
Concentration of mixture = total moles of ion
total volume of mixture

3. C = 0.5 mol/L  n = CxV  C = 0.75 mol/L n = CxV = 0.05 mol 0.05 mol
V = 0.100L
C = 0.5 mol/L 
MgCl2(aq)  Mg2+ (aq) Cl- (aq)
n = CxV
= 0.05 mol
0.05 mol
0.10 mol
Mg2+
Cl-
Cl-
V = 0.200L
C = 0.75 mol/L 
MgS(aq)  Mg2+ (aq) S2- (aq)
n = CxV
= 0.15 mol
0.15 mol
0.15 mol
Mg2+
S2-

4.   +  +  V = 0.100L Cmixture = nT n = 0 mol VT H2O
[Mg2+] = mol mol
0.400 L
= mol/L
 +  + 
[Cl-] = mol
0.400 L
= mol/L
Cl-
Mg2+
[S2-] = mol
0.400 L
= mol/L
[Mg2+] is 0.50 M,
[Cl-] is 0.25 M
and [S2-] is 0.50 M
S2-
V = 0.400L

5. What is the minimum volume of 0
What is the minimum volume of 0.25 mol/L magnesium chloride, MgCl2 (aq), needed to precipitate all the silver ions in 60 mL of 0.30 mol/L silver nitrate, AgNO3 (aq)?
MgCl2 (aq) + 2AgNO3 (aq)  2AgCl(s) + Mg(NO3)2 (aq)
2x1 n C V
mol
0.018 mol
n = CxV
0.25 mol/L
0.30 mol/L
0.036 L
0.060L
V = n/C
the volume of MgCl2 needed is 36 mL.

6. Calculate the mass of silver chromate that forms when 50. 0 mL of 0
Calculate the mass of silver chromate that forms when 50.0 mL of mol/L silver nitrate reacts with 25.0 mL of mol/L sodium chromate.
2AgNO3 (aq) Na2CrO4 (aq)  Ag2CrO4 (s) NaNO3 (aq)
2x1 n C V m M LR
0.005 mol
mol
mol
0.100 mol/L
0.150 mol/L
0.050 L
0.025L
0.829 g
m = nxM
331.7 g/mol
mol
mol
n = CxV
the mass of Ag2CrO4 that will form is g.

7. HOMEWORK CAN I … … determine the concentration of ions in a solution
… use Stoichiometry to find the minimum volume required to precipitate an ion
… use Stoichiometry to find the mass of a precipitate when two aqueous solutions are mixed
HOMEWORK
p421 #1-10