Transcript Unit 14: Solutions

Factors affecting
Solubility
Get out your lab to
complete it
Solutions are Mixtures
The Solution Process
Factors
Affecting the Rate
of Dissolving
1)
Crushing/Grinding
It reduces the particle size
and increases the surface
area of the solute exposed to
the solvent
2)
Agitation (stirring) - Brings
“fresh” solvent into contact with
the solute. (more collisions)
 3)
Heating the solvent- Increases
the kinetic energy (moving faster)
of the solvent molecules causing
more frequent collisions between
the solvent and solute.
Solubility and Factors affecting
solubility

Solubility- the amount of a
substance required to form a
saturated solution with a
specific amount of solvent at
a specific temp.
 ex:
the solubility of sugar in water
is 204 g/100 ml of water at 20oC.
The Solution Process
 Consider
a sugar solute with a
solubility (s) of 204 g per 100ml
water. The volume in the diagram
is 50 mL.
80g/50ml 102 g/50ml 120g/50ml
The Solution Process
1)
Saturated solution- a
solution that contains the
maximum amount of dissolved
solute
(solubility=204g/100ml)
80g/50ml 102 g/50ml 120g/50ml
The Solution Process
2)
Unsaturated solution- a
solution that contains less
solute than a saturated
solution
(solubility=204g/100ml)
80g/50ml
102 g/50ml 120g/50ml
The Solution Process
3)
Supersaturated solutiona solution that contains more
solute than a saturated
solution at the same
conditions
(solubility=204g/100ml)
80g/50ml
102 g/50ml
120g/50ml
Miscibilty
The Solution Process
Different solvents have the
ability to dissolve different
amounts of solute.
The key is the nature of the
solute and the nature of the
solvent.
The Solution Process
C.
“Like dissolves like”-
solubility of a substance
is related to the nature
of the solvent.
NATURE OF THE SOLUTE
POLAR WILL DISSOLVE:
 Polar substances
 Ionic compounds
NONPOLAR WILL
DISSOLVE:
 Nonpolar molecules
 covalent compounds
 Alcohols
The Solution Process
1)
“like dissolves like”- like
refers to the polarity of the
solute and solvent
 a) ex: water will dissolve
salt because salt is ionic and
water is polar
The Solution Process
b) ex: oil will not
dissolve in water
because oil is
nonpolar and
water is polar
The Solution Process
miscible
(soluble)- Alcohols
are miscible in
water (dissolves in
all proportions)
because they are
both polar
The Solution Process
Immiscible (not
soluble)- oil is
immiscible in
water.
Solvation:
Process that
occurs when a solute
dissolved. Ions or molecules
become completely
surrounded by solvent
molecules
Solubility Curve
A
graph that indicates how
likely a solute is to dissolve
in a solvent at any given
temperature.
(g solute/100 g solvent)
Solubility
of solids
The Solution Process
(Temperature)
Solubility of a substance is
related to temperature of the
solution
Temperature affects solids and
gases differently.
Solids increase in solubility
Gases decrease in solubility
The Solution Process
(Pressure)
Solubility of a gas is related to
pressure being exerted on the
solvent
Pressure only affects the
solubility of gases. Solubility of
liquids and solids is not changed
by changes in pressure.
 a)
Reason for sodas
“bubbling up” when the
top of a soda bottle is
open.
 When
the bottle is
opened, there is a rapid
decrease in the pressure
and the solubility of
carbon dioxide gas in the
water is greatly reduced
causing the familiar
bubbling and foaming.
b)
This rapid escape of a gas
from a liquid is called
effervescence.
 E.
Solubility of
a substance is
related to
temperature of
the solvent.
 1) Gases will
always have
greater
solubility in
cold solvents.
Types of Mixtures: Solutions
Ionic solutions- solutions composed
of ions that are free to move
throughout the solution
a) Electrolyte- Can conduct an
electric current;
acids, bases & salts
Ex: NaCl in water
Ex: Tap water
Solutions in which the solute
is composed of neutral
molecules
Non-electrolyte- cannot
conduct electric currents;
covalent compounds (except
acids)
Ex: Sugar in pure water
The Solution Process
Water
molecules are in
continuous motion.
When a solute is added 
the water molecules will
collide with it.
The Solution Process
The
water molecules attract
the solute particles and the
particles will break away.
The Solution Process
Solvation:
The process that
occurs when a solute
dissolves
– ions or molecules become
solvated or surrounded by
solvent molecules