Solutions
Homogeneous mixtures of 2 or more substances
Can be:
Solid Sterling
SilverGas
Air
Liquid
**Used most
frequently
in
chemistry**
Solution Components:
Solvent
Solute
the component present in the greatest amount
all other components dissolved in solvent
Aqueous Solutions
Solvent
Solute
WATER
Whatever is dissolved in the water
In chemical equations, denoted as aqueous (aq)
WATERUniversal solvent
POLAR molecule
Oxygen has higher electronegativity than Hydrogen so it pulls the bonded electrons closer to it giving it a partial negative charge
δ+
δ+
δ-
How things dissolve in
1) Ionic
Compounds
(Salts)
Ionic compounds dissociate into component
ions & surrounded by water molecules
(solvated)
WATER
Compound of cation & anion (normally metal + nonmetal)
How things dissolve in
2) Covalent
Compounds
(Molecules)
WATERCompounds of nonmetals
Molecular substances dissolve without forming ions -water molecules surround molecules
*EXCEPTION: Acids/Bases
How things dissolve in
3) Acids & BasesWATER
Form IONS in solution
Acids usually have Hydrogen at start of chemical formula or contains COOH group
Electrolyte & NonelectrolyteElectrolyte: a substance whose aqueous solutions contains ions
Nonelectrolyte: a substance whose aqueous solutions does not contain ions
Ions are able to carry electrical charge to and from electrodes—conduct electricity
No ions to carry electrical charge to and from electrodes— do not conduct electricity
Identifying ElectrolytesStrong electrolyteWeak electrolyteNonelectrolyte
Ionic
Molecular
All None None
Strong Acids
Weak Acids/Base
s
All other compounds
Strong Acids Strong BasesHClHBrHIHClO3HClO4HNO3H2SO4 (first proton)
Group 1A metal HydroxidesHeavy Group 2A Hydroxides
[Ca(OH)2, Sr(OH)2, Ba(OH)2]
Equations of Strong/Weak Electrolytes
HCl (aq)
H+ (aq)+ Cl- (aq)
CH3COOH (aq) H+ (aq)+ CH3COO- (aq)
Half arrows in opposite direction indicate chemical equilibrium- forward reaction
is equal to rate of backward reaction
In this case, molecules are ionizing and ions are recombining to form molecules
BaF2
*water molecules not shown for simplicity*
2+
- 2+2
+
2+
-
--
-
--
Electrolyte or Nonelectrolyte?
Strong or Weak?
Ions present?
-Ba2+
F-
Electrolyte or Nonelectrolyte?
Strong or Weak?POP QUIZ
Solution of:MgCl2
KClK2SO4
*water molecules not shown for simplicity*
2-
2- 2-
2-
+ +
+
+
+
++
+Extra Credit: Write the correctly balanced electrolyte equation that the picture could represent.
Precipitate ReactionsReaction in which two aqueous solutions produce an insoluble product called a precipitate
Solubility RulesSoluble Compounds Contain:C2H3O2 - , CH3COO-
NH4+
NO3-
CN-
ClO-
ClO2-
ClO3-
ClO4-
Br-
Cl-
I-
SO4-2
Common Exceptions:NoneNoneNoneNoneNoneNoneNoneNone
Compounds of Ag+, Pb2+, Hg2+2
Compounds of Ag+, Pb2+, Hg2+2
Compounds of Ag+, Pb2+, Hg2+2
Compounds of Sr+2, Ba+2, Pb+2, Hg2+2
Insoluble Compounds Contain:CO3
-2
PO4-3
CrO4-2
Cr2O7-2
OH-
S-2
Common Exceptions:Compounds of NH4
+ & Alkali MetalCompounds of NH4
+ & Alkali MetalCompounds of NH4
+ & Alkali MetalCompounds of NH4
+ & Alkali MetalCompounds of NH4
+ Alkali Metal, Ca+2, Sr+2, and Ba+2
Compounds of NH4+ Alkali Metal, Ca+2, Sr+2, and Ba+2
Ag2SO4 (aq) + Na(NO3) (aq)
2-
2-
+
++
+
- +-
- -+
+
+
+ 2-
2-
+
++
+-
+-
--
+
+
+
Both products soluble= no reaction
Ionic Equations & Spectator Ions2KI(aq) + Pb(NO3)2(aq) PbI2(s) + 2KNO3 (aq)Chemical Equation: shows chemical formulas without indicating ionic character
Complete Ionic Equation: all soluble strong electrolytes shown as ions2K+(aq) + 2I-(aq)+ Pb2+(aq)+2NO3
-(aq) PbI2(s)+2K+
(aq)+2NO3-(aq)
Net Ionic Equation: only the ions and compounds directly involved in reaction shown
Ions that appear in identical form on both sides of ionic
equation are called spectator ions- they don’t play a role in the reaction
2I-(aq)+ Pb2+(aq) PbI2(s)
Concentration of SolutionsConcentration: amount of solute dissolved in given quantity of solvent or quantity of solution
Molarity (M)Way to measure the concentration of a solutionNumber of moles of solute in a liter of solution
moles solutevolume of soln
(L)Molarity =
molV
M =
Practice!Calculate the molarity of a solution made by dissolving 23.4g of sodium sulfate in enough water to form 125mL of solution.
Practice!A solution of HNO3 has a concentration of 0.200M; how many moles does a 2.0L solution contain?
Making Solutions•Mass appropriate amount of solute•Add to container (volumetric flask, beaker, Erlenmeyer flask etc)•Add water, swirl to dissolve•Continue to add water until required volume of solution reached
DilutionProcess of making a lower concentration solution from a higher concentrated solution.
HOW???Add WATER
Dilution**Since you’re not changing the amount of solute:**
Mol of solute before dilution = mol of solute after dilution
molV
M =
M1V1 =M2V2
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