Solution Chemistry and Solubility

12A—Demonstrate and explain effects of temperature and the nature of solid solutes on the

solubility of solids

13A—Compare unsaturated, saturated, and supersaturated solutions

13B—Interpret relationships among ionic and covalent compounds, electrical conductivity, and

colligative properties of water

Review

Element—substance that cannot be broken down into simpler substances (periodic table)

Compound—a substance made of atoms of more than one element bound together (H2O, CO2, NaCl)

Mixture—a combination of more than one pure substance (Salt water, Powerade, Salad)

Mixture Review

Mixture—a physical blend of two or more substances

Heterogeneous mixture—one that is not uniform in composition

Homogeneous mixture—one that has a completely uniform composition

Mixture Review

Mixture REVIEW You can separate mixtures by PHYSICAL

means Distillation Separation Chromatography

Type Particle size

Settle upon standing

Tyndall effect (Scatter light)

Solutions Homo-geneous

0.01-1 nm No no

Colloid Hetero-geneous

1-1000 nm No Yes

Suspension Hetero-geneous

Greater than 1000 nm

Yes sometimes

Solution Chemistry Solution—a homogeneous mixture Solute—dissolved particles in a solution Solvent—the dissolving medium in a

solution (usually water, the universal solvent)

Kool-Aid Solution

Kool-Aid Juice is the SOLUTION Kool-Aid powder and Sugar are the

SOLUTES Water is the SOLVENT

Soluble vs. Insoluble

Soluble—dissolves completely so that solution looks transparent (free of any floating particles

Insoluble—does not dissolve completely; solution is cloudy

How does dissolving takes place?

What happens when salt is dissolved in water?

NaCl Na+ + Cl-

Complete the dissociation of the following salts:

KCl K+ + Cl-

MgCl2 Mg+2 + 2Cl-

AlCl3 Al+3 + 3Cl-

MgF2Mg+2 + 2F-

Solution Chemistry Electrolytes—compounds that conduct an

electric current ALL ionic compounds; NaCl, CuSO4, NaOH

Nonelectrolytes—Compounds that do not conduct an electric current in either aqueous solution or the molten state Many molecular compounds; carbon, sugar,

alcohol

Electrolytes vs. Nonelectrolytes

Electrolytes vs. Nonelectrolytes Some very polar molecular compounds are

nonelectrolytes in pure state but become electrolytes when dissolved in water

NH3(g) + H2O(l) NH4+(aq) + OH-(aq)

Electrolytes vs. Nonelectrolytes

Weak Electrolyte—only a fraction of the solute exists as ions

Strong Electrolyte—almost all the solute exists as separate ions

Weak Electrolyte in Weak Electrolyte in solution.solution.

Strong electrolyte Strong electrolyte in solution.in solution.

Electrolytes vs. Nonelectrolytes

STRONG ELECTROLYTES Strong acids (HCl, H2SO4, HNO3) Strong bases (NaOH, KOH)

WEAK ELECTROLYTES Weak acids (Vinegar, acetic acid, CH3COOH)

Weak bases (Ammonia, NH3)

NONELECTROLYTES Molecular compounds Nonmetal bonded to nonmetal

Electrolytes vs. Nonelectrolytes

More ions in solutions, the more conductivity Which salt would give more ions: NaCl or

MgCl2?

So, which will conduct electricity more/be a better electrolyte?

Look back at the dissociation reactions and determine the better electrolyte.

Solutions are homogeneous mixtures that could be solid, liquid, or gaseous

Gas Gas Oxygen in nitrogen

Gas Liquid CO2 in water

Liquid Gas Water in air

Liquid Liquid Alcohol in water

Liquid Solid Mercury in silver and tin (dental amalgam)

Solid Liquid Sugar in water

Solid Solid Copper in nickel (alloys)

Solubility Solubility—the amount that dissolves in a

given quantity of a solvent at a given temperature to produce a saturated solution. Solubility is often expressed in grams of solute

per 100g of solvent

Water and Solubility?

REMEMBER water is a POLAR molecule Polar means electrons are not spread evenly

throughout the molecule

Polar molecules dissolve polar molecules Water can dissolve ammonia

Nonpolar molecules dissolve nonpolar molecules Octane (gasoline) can dissolve CO2

LIKE DISSOLVES LIKE!!!!LIKE DISSOLVES LIKE!!!!

Solution Concentration

Concentration—the quantity of solute dissolved in a given quantity of solution Three ways to describe a solution

Unsaturated solutionSaturated solutionSupersaturated solution

Solubility

Unsaturated—a solution that contains less solute than solvent

Saturated—a solution that contains the maximum amount of solute for a given amount of solvent at a constant temperature

Supersaturated—a solution that contains more solute than it can theoretically hold at a given temperature; crystals form

Solubility

Two liquids are said to be MISCIBLE if they dissolve in each other Water and ethanol dissolve in each other

Liquids that are insoluble in each other are IMMISCIBLE. Oil and water do no dissolve in each other

MISCIBLE

Water and alcohol

IMMISCIBLE

Water and oil

Gas Solubility

Henry’s Law—as the pressure of the gas above the liquid increases, solubility of the gas increases and vice versa

Gas Solubility

Henry’s Law

S = solubility P = Pressure

S1 S2

P1 P2

=

Gas Solubility

EXAMPLES Ears Popping Underwater Diving (the bends) Airplane taking off or landing

Factors Affecting Solubility

SURFACE AREA Solutes with larger surface area dissolves faster

Smaller pieces dissolve faster than larger pieces

Factors Affecting Solubility

STIRRING Stirring or shaking a solution helps the solute

dissolve fasterStirring or shaking moves dissolved sugar away from

undissolved sugar crystals

Factors Affecting Solubility

TEMPERATURE Solutes dissolve faster when the solvent is hot

When substance is heated, particles move faster causing more collisions between particles

Factors Affecting Solubility

Things that dissolve in water are called SOLUBLE

Things that do not dissolve in water are called INSOLUBLE

Solubility Curves

Solubility curves (graphs) give the solubility and temperature of a saturated solution.

Solubility is on y-axis Temperature (°C) is on x-axis

Solubility Curve

Solubility Curves

SATURATED solution is ON line or curve UNSATURATED solution is BELOW line

or curve SUPERSATURATED solution is above line

or curve