SOLUBILITY

SolubilitySolubilitySolubility

how many grams of solute that will dissolve in 100 g of solvent to make it saturated at a given temperature

Dissolution- the rate at which a substance dissolves

FACTORS AFFECTING SOLUBILITY

Polarity

Factors Affecting Solubility

Temperature

Surface Area

Stirring

Pressure

Particle size – area of solute particles exposed to the action of the solvent particles. Increase in surface area of the solute particles , solubility increases

Example: fine table salt dissolves faster than rock salt

SURFACE AREA

Stirring or Agitation increases the solubility of solid solute particles in a solvent. Because it speeds up the contact between the surface of the solute and the solvent particles

AGITATION

Effect of Temperature on Solubility of Solids and Liquids

• Generally, increasing the temperature will increase solubility of solids and liquids.

• Application of heat - solvent molecules move faster and come in contact frequently with the solute particles, increasing solubility.

Solubility Curves

LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

0 10 20 30 40 50 60 70 80 90 100

Solubility vs. Temperature

Sol

ubili

ty (

gram

s of

sol

ute/

100

g H

2O)

KI

KCl

20

10

30

40

50

60

70

80

90

110

120

130

140

100

NaNO3

KNO3

HCl NH4Cl

NH3

NaCl KClO3

SO2

shows the dependence

of solubility on temperature

gases

solids

But increasing temperature will lower the solubility of gases (the gas will escape from solution, going back to the gas phase).

Effect of Temperature on Solubility of Solids and Liquids

Figure 13.18

To

Sol.

To

Sol.

Solids dissolved in liquids Gases dissolved in liquids

As To , solubility As To , solubility

• Thermal pollution: if lakes get too warm, CO2 and O2 become less soluble and are not available for plants or animals.

• Warm Pop

Making ConnectionsMaking Connections

The Effect of Pressure on the Solubility of Gases

• Pressure has no effect on the solubility of solids and liquids but has a strong effect on the solubility of gases.

• The solubility of gases increases when the pressure above the gas is increased. In other words, more gas will dissolve when pressure is increased. This is known as HENRY’S LAW (William Henry, English chemist).

Pressure Effects

Figure 13.14: Factors Affecting SolubilityFigure 13.14: Factors Affecting Solubility

Henry’s Law

Sg = kPg

where• Sg is the solubility of the

gas;• k is the Henry’s law

constant for that gas in that solvent;

• Pg is the partial pressure of the gas above the liquid.

• Nitrogen narcosis, the “bends” • Soda

Making ConnectionsMaking Connections

http://www.youtube.com/watch?v=LfCOnGHheok&feature=fvst

Solutions

How does a solid dissolve into a liquid?

What ‘drives’ the dissolution process?

Polarity Solute – Solvent Interactions

• Intramolecular Bonding

• Intermolecular Bonding

Intramolecular Bonding

• Intramolecular bonding refers to the chemical bonding that holds atoms together within a molecule of a compound

Covalent bonding and ionic bonding are the two main types of intramolecular bonding

• Ionic bonding involves the transfer of valence electrons from one atom to another.

• The electrostatic attraction between opposite charged ions holds the molecule (formula unit) together. An example is sodium chloride, NaCl, which involves the attraction between Na+ and Cl- ions.

IONIC BONDING

Covalent bonding involves the sharing of valence electrons between two atoms. Eg. covalent bonding holds hydrogen and oxygen atoms together to form a water molecule, H2O.

POLAR- unequal sharing of electronsNON POLAR – equal sharing of electrons

COVALENT BONDING

NON POLAR MOLECULE

• Nonpolar molecules either have no positive and negative ends, because the bonds making up the molecule are nonpolar, or because the entire outer "edge" is negative while the core of the molecule is positive (or vice versa), thus having no oppositely charged ends.

POLAR MOLECULE

• A polar molecule will have one end of the molecule bearing a partial positive charge while another end carries a partial negative charge. Polar molecules must contain polar bonds.

The oxygen end of the molecule has a partial negative charge (δ-), while the hydrogen end is partially positive (δ+).

Intermolecular Bonds occur between molecules

How Does a Solution Form?Solvent molecules cluster around the solute particles. If the intermolecular attraction between the solvent and solute is stronger than between the solute –solute or solvent-solvent molecules, then a solution forms.

“like dissolves like”Two substances with similar intermolecular forces are likely to be soluble in each other.

• non-polar molecules are soluble in non-polar solvents

CCl4 in C6H6

• polar molecules are soluble in polar solvents

C2H5OH in H2O

• ionic compounds are more soluble in polar solvents

NaCl in H2O or NH3 (l)

12.2

SOLUTE POLAR SOLVENT

NONPOLAR SOLVENT

Ionic Soluble Insoluble

Polar Soluble Insoluble

Nonpolar Insoluble soluble

Vitamins• Water Soluble

– Vitamin C– Must be replenished regularly

• Fat Soluble– Can overdose (liver damage,

hair loss, blurred vision, numbness)

– Vitamin A– Can be ingested periodically,

stored in body fat

Making ConnectionsMaking Connections

Factors Affecting Solubility• Vitamin A is soluble in nonpolar compounds (like

fats).• Vitamin C is soluble in water.

Watch video and write down explanation on sheet provided.

How Salt Dissolves? ION-POLE ATTRACTION

How Salt Dissolves? ION-POLE ATTRACTION

• Each ion in the solute is surrounded by the partial positive and negative solvent molecules in the water.

• Solute is pulled out of its lattice and solvent molecules spread the solute out throughout the solution.