Solubility Factors

SOLUTE

Solutions
SOLVEN
& Solubility
T

Solutions
& Solubility

Solutions
& Solubility

SOLVENT SOLUTION SOLUTE
In a solution, the A homogenous Other substances
solvent is present in mixture present in a solution
the largest amount (looks uniform other than the
by volume, mass, or throughout) solvent.
number of moles

Solutions
& Solubility
 ACTIVITY 1: Examples of Solutions
Observe the samples of solutions and classify each solution under one category:

Original state of solute Solvent Example

Gas Gas
Oxygen in air
Gas Liquid CO2 in pop
Hydrogen in palladium
Gas Solid

Liquid Gas Water droplets in air

Liquid Liquid Alcohol in water
Amalgams
Liquid Solid
(i.e. mercury in silver)

Solid Gas
Dust in the air
Solid Liquid Sugar in water

Solid Solid Copper in bronze
3

Solutions
& Solubility
Hydrogen in palladium: A method for storing hydrogen gas
as fuel

Solutions
& Solubility
Amalgam: A metal and mercury solution

By mass: 43% to 54% mercury,
~20-35% silver, ~10% copper,
~2% zinc, and some tin

Remains soft for a
short time and then
forms a hard and
durable compound

Solutions
& Solubility
Identify the components of these solutions:

Solutions
& Solubility
Common Types of Solutions:

Alloys: Solid solutions of metal

Stainless steel: Iron, chromium, nickel, manganese, vanadium

Solutions
& Solubility

Alloys: Solid solutions of metal

Brass: Copper and zinc

Solutions
& Solubility
Liquid solution: A solution with two or more miscible liquids

Miscible = Can dissolve in Immiscible = Cannot dissolve
one-another in one-another

Rubbing alcohol Oil and water

Solutions
& Solubility
Gas solution: A solution of two or more gases

Air: 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide

Solutions
& Solubility
Aqueous solution: A solution where water is the solvent

Tap water

Solutions
& Solubility
AQUEOUS SOLUTIONS: SOLUBLE VS. INSOLUBLE
Not all substances dissolve equally in water.
Recall the solubility table (dissolving solids in water):

Although substances are classified as
either soluble or insoluble in this table,
substances are almost never completely
insoluble or completely soluble in
water.

The solubility of a solute is the amount of
solute that dissolves in a given quantity of
solvent, at a certain temperature.

For example, the solubility of sodium
chloride in water at 20ºC is 36g per
100mL of water.

Solutions
& Solubility
AQUEOUS SOLUTIONS: SOLUBLE VS. INSOLUBLE

Soluble Partly or Insoluble
slightly
soluble
More than 1g in Between 1g Less than 0.1g
100mL and 0.1g in in 100mL
OR 100mL OR
greater than OR Less than
0.1mol/L Between 0.01mol/L
0.1mol/L and
0.01mol/L

Solutions
& Solubility
AQUEOUS SOLUTIONS: SATURATED VS. UNSATURATED
One cannot endlessly dissolve salt in water

Solutions
& Solubility

Saturated solution:
Formed when no more solute will
dissolve in a solution, with excess
solute present.

Unsaturated solution:
A solution that is not yet saturated

Supersaturated solution:
Formed when a solution dissolves
more solute than allowed at a
specific temperature. No excess
solute is present.

Solutions
& Solubility

In a saturated solution with
excess solute present, the
rate of dissolution and
precipitation are the same

PbSO4(s) Pb2+(aq) + SO42-(aq)
precipitate dissolved ions

Solutions
& Solubility
FACTORS THAT AFFECT THE RATE OF
DISSOLVING AND SOLUBILITY
ACTIVITY 2: Who Can Dissolve the Most Salt?

Solutions
& Solubility
FACTORS THAT AFFECT THE RATE OF DISSOLVING AND SOLUBILITY

ACTIVITY 2: Who Can Dissolve the Most Salt? (10 min)
1) Work in groups of 3-4
2) Each group will be given a graduated cylinder of salt and 250mL
of water
3) Try to dissolve as much salt as you can
4) Try to alter the physical properties of your solvent and solute to
increase the amount of salt that you can dissolve
5) You cannot add water
6) You must not have precipitate in your solution, and your
solution cannot be boiling.

Solutions
& Solubility
FACTORS THAT AFFECT THE RATE OF DISSOLVING AND SOLUBILITY

ACTIVITY 2: Who Can Dissolve the Most Salt?
Factor Affect on rate of dissolving/solubility

Temperature Higher temperatures allow more
molecules to dissolve

Agitation Stirring/agitation allows more
molecules to dissolve

Surface area Increasing the surface area allows
more molecules to dissolve

Solutions
& Solubility
Temperature

WARMER COOLER
At higher temperatures, solvent molecules
move faster, and collide with undissolved
solid molecules more frequently

Solutions
& Solubility
Agitation

MORE MOLECULES IN FEWER MOLECULES IN
CONTACT CONTACT
Agitation brings fresh solvent into contact with
undissolved solid

Solutions
& Solubility
Surface Area
Molecules on the
inside are exposed,
enabling them to
collide with solvent
molecules

LOWER SURFACE AREA HIGHER SURFACE AREA
The greater the surface area of the reactant,
the greater the molecules are in contact with
the solvent

Solutions
& Solubility
Factors that affect solubility

Solutions
& Solubility
1) Molecule polarity

- Compounds dissolve due to the intermolecular forces
between solvent and solute molecules
Sugar: Forms H-bonds with water
H
O

H
H

O

H
H

O

H
O
H

H
H

H
H
H
O
O

O
H

Solutions
& Solubility

Ethanol: Forms H-bonds with water

H
O H

O
H

H
H
O
H

Solutions
& Solubility

Methanol: Forms H-bonds with water

Solutions
& Solubility

Octane: Cannot form H-bonds with water
H
H

O

Solutions
& Solubility
Which has greater solubility in water?

CH3OH vs. CH3CH2CH2CH2CH2CH3OH

Which has greater solubility in oil?

CH3OH vs. CH3CH2CH2CH2CH2CH3OH

The more attractive intermolecular forces exist
between solvent and solute molecules, the
greater the solubility

Solutions
& Solubility

The addition of
solute raises
the boiling point
of a solvent

Solutions
& Solubility
2) Temperature

- Greater temperatures result in greater solubility of
most solids
Which has greater solubility in water?

Instant coffee powder + water at 20°C vs. Instant coffee powder + water at 70°C

Solutions
& Solubility
2) Temperature

- The greater the temperature,
the lower the solubility of
gases

As temperature increases,
gas molecules gain kinetic
energy and are able to
leave a solution. Gases
become LESS soluble with
increasing temperature.

Solutions
& Solubility
3) Molecule charge

- Molecules that are charged can form dipole-ion
attractions or Van der Waals forces between solute and
solvent molecules H H

O O

H H
H

H
H

H
Na+ Cl-
O

O
O

O
H

H
H

H
H H

O O

H H

Salt: Ions exert dipole-ion attractive forces with water

Solutions
& Solubility
Factors that affect ion solubility

Solutions
& Solubility
1) Ion charge

- Ions with small charges tend to be soluble
- Increasing the charge increases the force that holds the
ions together
- (i.e. phosphates, PO43+, tend to be insoluble)

1+ 1- 3+ 3-

Solutions
& Solubility
2) Ion size

- Small ions tend to be less soluble than large ions
- Small ions bond more closely together than large ions
- Thus the bond between small ions is stronger than the
bond between large ions with the same charge

2+ 2- 2+ 2-

Solutions
& Solubility
Net Ionic Equations Use the
solubility
Chemical equation: table

K2CO3(aq) + CuSO4(aq)  ?K2SO4(aq) + CuCO3(s)

Ionic equation:
 Anything that is aqueous must be separated into its component ions

2K+(aq) + CO32-(aq) + Cu2+(aq) + SO42-(aq)  2K+(aq) + SO42-(aq) + CuCO3(s)

Net Ionic equation:
 Spectator ions* are eliminated

Cu2+(aq) + CO32-(aq)  CuCO3(s)

*Spectator ions are ions that do not participate in the actual reaction

Solutions
& Solubility
Solubility curves
A graph that displays the
maximum solute that can dissolve
in 100g of water at various
temperatures.

Why does the solubility curve of
NH3 have a negative slope?

NH3 is a gas. Gases become LESS
soluble with increasing
temperature.

Solutions
& Solubility
Solubility curves

1) Is 50g of NH4Cl in 100g of
water at 40ºC saturated,
unsaturated, or supersaturated?
Supersaturated

2) How many grams of KNO3 can
dissolve in 50g of water at 70ºC?
65g

3) How much water is required to
dissolve 60g of NaNO3 at 50ºC?
115g NaNO3 = 60g NaNO3
100g water x
x = 52g water

Solubility Factors

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Solubility Factors

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