Chapter 6
Solutions and Colloids
Chemistry B11
Mixture: is a combination of two or more pure substances.
Homogeneous: uniform and throughout
Air, Salt in water
Heterogeneous: nonuniform
Soup, Milk, Blood
Mixtures
Solution
Solutions
Gas in gas (air) solid in solid (alloys) liquid in liquid (alcohol in water)
Gas in liquid (cokes) solid in liquid (sugar in water)
Solutions
Well-mixed (uniform) – single phase
homogenous
transparent
cannot be separated by filtration
cannot be separated on standing
sugar in water
Solutions (liquid in liquid)
Solvent: greater quantity (water)
Solute: smaller quantity (sugar)
Immiscible: two liquids do not mix.
miscible: two liquids can mix. alcohol in water (in any quantities)
for liquid in liquid
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
Seeding
A surface on which to being crystallizing.
Supersaturated solution
gas in liquid: T ↑ Solubility ↓
Global Warming
Pressure and Solutions
P Solubility (gas in liquid)Henry’s law
Concentration
Concentration: amount of a solute dissolved in a given quantity of solvent.
1. Percent concentration:
Weight / volume (W / V)% =Weight solute
Volume of solution (mL)× 100
Weight / Weight (W / W)% =Weight solute
Weight of solution× 100
Volume / volume (V / V)% =Volume solute (mL)
Volume of solution (mL)× 100
2. Molarity (M): number of moles solute dissolved in 1 L of solution.
Concentration
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
3. Parts per Million (ppm):
Concentration
ppm =g soluteg solvent
× 106
Parts per billion (ppb):
ppb =g soluteg solvent
× 109
Dilution
Concentrated solution(Stock solution)
Dilute solution
Dilution
M1V1 = moles(n) before dilution
M2V2 = moles(n) after dilution
M1V1 = M2V2
% V1 = % V2
Equivalent
Number of Equivalents (Eq) in 1 mole of each ion is number of charges of that ion.
Ion Charge # of Equivalents in 1 mole
Na+ 1+ 1 Eq
Ca2+ 2+ 2 Eq
Fe3+ 3+ 3 Eq
Cl- 1- 1 Eq
SO42- 2- 2 Eq
Equivalent
Ex. 1: How many equivalents of CO32- are in 1 mole of Al2(CO3)3?
The charge of CO32- is 2- → 1 mole Al2(CO3)3 has 2 Eq CO3
2-.
Ex. 2: How many equivalents of Fe3+ are in 5 mole of Fe2O3?
The charge of Fe3+ is 3+ → 1 mole Fe2O3 has 3 Eq.
5 moles: 5 × 3 = 15 Eq
Water in our body
1. About 60% of our body.
2. Most of the reactions occur in aqueous solution.
3. Participates in many biochemical reactions.
4. Transports reactants and products from one place in our body to another.
5. Eliminates the waste materials from cells and our body (urine).
Solvent and Solute
polar dissolves polar
Nonpolar dissolves nonpolarlike dissolves like
Ions Hydrated by H2O
Hydration
Solvent and Solute
Most chlorides (Cl-) and sulfates (SO42-) are soluble in water.
(except AgCl, BaSO4, and …)
Most carbonates (CO32-), phosphates (PO4
3-) and hydroxides (OH-) are insoluble in water.
(except NaOH, LiOH, KOH, and NH4OH)
All nitrates (NO3-) and acetate (CH3COO-) are soluble in water.
Electrolytes
+ -
electrolyte
Electrolyte: conducts an electric current.
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).
NaCl → Na+ + Cl-
Na+Cl-
bulb
Ionization (Dissociation)
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 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)
suspension: system does not stays stable and settle (> 1000 nm). (sand in water)
Suspension
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.
Freezing and boiling point
If we dissolve a solute in a solvent: bp fp
ΔT = ikMΔT: change of bp or fp (T2 - T1)i: number of particlesK: constant (depend on solute) – Kb Kf
M: molarity
NaCl Na+ + Cl- i = 2
C2H6O2 i = 1
K2SO4 2K+ + SO42- i = 3
osmotic pressure
Osmotic Pressure
Semipermeable membrane
Higher concentration → Higher osmotic pressure
Osmotic Pressure
Water flows from low concentration
tohigh concentration.
Osmotic Pressure
Osmolarity (osmol) = M × i
M: molarityi: number of particles
Osmolarity ↑ → Osmotic pressure ↑
Hemolysis Crenation
Isotonic solution Hypotonic solution Hypertonic solution
The most typical isotonic solutions
0.9% (m/v) NaCl
5% (m/v) Glucose
0.9 g NaCl/100 mL of solution
5 g glucose/100 mL of solution
Higher than these numbers → Hypertonic solution
Lower than these numbers → Hypotonic solution
Dialysis
Dilute solution