Chemistry B2A
Chapter 15
Solutions
Mixtures
Mixture: is a combination of two or more pure substances.
Homogeneous: uniform and throughout
Air, Salt in water
Solution
Heterogeneous: nonuniform
Soup, Milk, Blood
Solutions
Gas in gas (air)
solid in solid (alloys)
Gas in liquid (cokes)
liquid in liquid (alcohol in water)
solid in liquid (sugar in water)
Solutions
Well-mixed (uniform) – single phase
homogenous
transparent
sugar in water
cannot be separated by filter
cannot be separated on standing
Solutions (liquid in liquid)
Solvent: greater quantity (water)
Solute: smaller quantity (sugar)
Immiscible: two liquids do not mix.
Miscible: two liquids can mix.
(in any quantities)
alcohol in water
Solvent and Solute
Polar dissolves polar
like dissolves like.
Nonpolar dissolves nonpolar
Hydrogen Bonds
Between H bonded to O or N (high electronegativity) → +ᵟ
and another O or N → -ᵟ
hydrogen
bond
H2O
H
-
O
-
+
H
H
hydrogen
bond
+
O
H
(a)
High boiling point
(b )
surface tension
(
Dissolving Ionic compounds
Ions Hydrated by H2O
Hydration
Electrolytes
bulb
Na+
Cl-
Electrolyte: conducts an electric current.
electrolyte
+
-
Ionization (Dissociation)
NaCl → Na+ + Cl-
strong electrolytes: molecules dissociate completely into ions (NaCl).
weak electrolytes: molecules dissociate partially into ions (CH3COOH).
nonelectrolytes: molecules do not dissociate into ions (DI water).
Solvent and Solute
All nitrates (NO3-) and acetate (CH3COO-) are soluble in water.
Most salts of Na+, K+, and NH4+ are soluble in water.
Most chlorides (Cl-) and sulfates (SO42-) are soluble in water.
(except AgCl, PbCl2, BaSO4, CaSO4, PbSO4)
Most carbonates (CO32-), phosphates (PO43-), Sulfide (S2-),
and hydroxides (OH-) are insoluble in water.
(except NaOH, KOH, Ba(OH)2, Ca(OH)2, and NH4OH)
Solutions
Saturated: solvent contains or holds all the solute it can (at a given T).
maximum solute that solvent can hold (Equilibrium).
Unsaturated: solvent can hold more solute (at a given T).
Is not the maximum solute that solvent can hold.
Supersaturated: solvent holds more solute that it can normally hold
(at a given T).
(more than an equilibrium condition)
Temperature and Solutions
Solubility: the maximum solute that will dissolve in a given amount of a solvent
(at a given T).
T
Solubility 
T
Crystal is formed.
Temperature and Solutions
T
Solubility 
Supersaturated solution
Seeding
A surface on which to
being crystallizing.
gas in liquid: T ↑
Solubility ↓
Global Warming
Pressure and Solutions
Henry’s law
P
Solubility  (gas in liquid)
Concentration
Concentrated solution: large amount of solute is dissolved.
Strong Coffee
Dilute solution: small amount of solute is dissolved.
Weak Coffee
Concentration
Concentration: amount of a solute in a given quantity of solvent.
1. Percent concentration:
Weight / volume (W / V)% =
Weight solute (g)
Volume of solution (mL)
Weight / Weight (W / W)% =
Weight solute (g)
× 100
Weight of solution (g)
Volume / volume (V / V)% =
Volume solute (mL)
× 100
× 100
Volume of solution (mL)
Concentration
2. Molarity (M): number of moles solute dissolved in 1 L of solution.
Molarity (M) =
moles solute (n)
volume of solution (L)
Molarity × V = number of moles (n)
prepare the solution: M, V → n (mol) → m (g)
Prepare the solution
prepare the solution: M, V → n (mol) → m (g)
m (g)
Volumetric flask
Concentration
3. Parts per Million (ppm):
g solute
ppm =
× 106
g solvent
Parts per billion (ppb):
ppb =
g solute
× 109
g solvent
Dilution
Concentrated solution
(Stock solution)
Standard solution: a solution with known concentration.
Dilute solution
Dilution
M1V1 = moles(n)
before dilution
Mole remains constant.
M2V2 = moles(n)
after dilution
M1V1 = M2V2
% V1 = % V2
Neutralization Reactions
We will talk about this in Chapter 16.
Normality
We will talk about this in Chapter 16.
Colloids
Solutions: diameter of the solute particles is under 1 nm.
Colloids: diameter of the solute particles is between 1 to 1000 nm.
non transparent, non uniform, large particles, cloudy (milky)
But it is a stable system.
Colloids
Tyndall effect:
You can see the pathway of the light passes
through a colloid. (particles scatter light.)
emulsion: a mixture of immiscible substances (liquid-liquid).
(milk and mayonnaise)
Brownian motion
Random motion of colloid particles.
Dust
Why do colloidal particles remain in solution and do not stick together?
1. Surrounding water molecules prevent colloidal molecules
from touching and sticking together.
2. A charged colloidal particle encounters another particle
of the same charge, they repel each other.
Suspension
suspension: system does not stays stable and settle (> 1000 nm).
(sand in water)
But it is not a stable system.