Chemistry of solutions

SOLUTIONS

D’ CHEMISTRY OF

SOME DEFINITIONSA solution is a

_______________ mixture of 2 or more substances in a single phase.

One constituent is usually regarded as the SOLVENT and the others as SOLUTES.

SOME DEFINITIONSSolutions are

homogeneous mixtures of two or more pure substances.

In a solution, the solute is dispersed uniformly throughout the solvent.

PARTS OF A SOLUTION

• SOLUTE – the part of a solution that is being dissolved

(usually the lesser amount)• SOLVENT – the part of

a solution that dissolves the solute

(usually the greater amount)• Solute + Solvent =

Solution

ACTIVITY 2.1 IDENTIFYING COMPONENTS OF SOLUTIONS

Solution Solute Solvent

Air in balloon

Ammonia water

Rubbing alcohol (70%)

Rubbing alcohol (40%)

Tincture of Iodine

Sea water

O2 N2

NH3 H2O

H2O Isopropyl alcohol

H2OEthyl alcohol

Iodine Alcohol

Salt H2O

WHICH IS WHICH 1st ROUNDIdentify the solute and solvent in each of the

following solutions.

1.0 g of sugar dissolved in 100 g of water. 50 mL of water mixed with 20 mL isopropyl alcohol A tincture of Iodine is prepared with 0.10 g I2 and 10.0 mL of

ethyl alcohol. 40 % ethanol a rubbing alcohol.

Sugar is the smaller quantity that is dissolving. Therefore it the solute and water is the solvent. Since both water and isopropyl alcohol are liquids, the one smaller volume, is the solute and

water is the solvent. Iodine is the solute and ethyl alcohol is the solvent. Ethanol is the solvent and water is the solute.

WHICH IS WHICH 2nd ROUNDIdentify the solute and solvent in each of the

following solutions.

10 g NaCl and 100 g of water. 50 mL ethanol and 10 mL H2O 2.0 L oxygen and 8.0 L nitrogen.100 g silver and 40 g mercury. 100 mL H2O and 5.0 g sugar

TYPE OF SOLUTION Gas Liquid Solid

SOLUTION SOLUTE SOLVENT EXAMPLE

Gas in a gas

Gas in a liquid

Liquid in a liquid

Solid in a liquid

Liquid in a solid

Solid in a solid

SOME EXAMPLES OF SOLUTION

AirOxygen Nitrogen

Soda waterCO2 H2O

VinegarAcetic acid H2O

Sugar syrupSugar H2O

Dental amalgamAgHg

Brass or SteelZinc CopperCarbon Iron

WATERD’ UNIVERSAL SOLVENT

H2O

FORMED?

HOW SOLUTIONS ARE

DEFINE SOLUTIONSSolutions are

homogeneous mixtures of two or more pure substances.

In a solution, the solute is dispersed uniformly throughout the solvent.

1. Solvent molecules attracted to surface ions.2. Each ion is surrounded by solvent molecules.3. Enthalpy (DH) changes with each interaction broken or formed.

How Does a Solution Form?

Ionic solid dissolving in water

The ions are solvated

(surrounded by solvent).If the solvent is

water, the ions are hydrated.

The intermolecular forces.

How Does a Solution Form?

solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute in the solution.

What is solvation?

Dilute small amount of solute dispersed in the solvent

Concentrated large amount of solute is dissolved in the solvent

KINDS OF SOLUTION

Types of Solutions Based on Solute Concentration…

Hypotonic(lower solute concentration) to the solution

Hypertonic(higher solute concentration) to the solution

Isotonic solutions are equal in their solute concentrations. We say that theyare isotonic to each other.

Types of Solutions Based on Solute Concentration…

How does a solid dissolve into a liquid?

What ‘drives’ the dissolution process?

What are the energetics of dissolution?

QUESTIONS THAT NEEDS SOLUTIONS…

• is the process by which a solid, liquid or gas forms a solution in a solvent.

WHAT IS DISSOLUTION ?

• In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent.

DISSOLUTION PROCESS IN SOLIDS…

• For liquids and gases, the molecules must be compatible with those of the solvent for a solution to form.

DISSOLUTION PROCESS IN LIQUIDS & GASES…

Dissolution vs Reaction

• Dissolution is a physical change—you can get back the original solute by evaporating the solvent.

• If you can’t, the substance didn’t dissolve, it reacted.

Ni(s) + HCl (aq) NiCl2(aq) + H2(g) NiCl2(s)dry

SOLUBILITY?DEFINE

What is Solubility?

• refers to the maximum amount of solute, expressed

in grams, that can be dissolved in 100 g of water at a specific temperature &

pressure.

Soluble a substance that dissolves in a solvent

Insoluble a substance that does not dissolve in a solvent (sand is insoluble in water)

VOCABULARY

LABORATORY ACTIVITY 2.7SOLUBILITY IN WATER

SUBSTANCES KEROSENE OILETHYL

ALCOHOL WATER

SugarSalt DetergentPowdered chalk Powdered charcoalSulfur powderCuSO4

KMnO4

INSOLUBLEINSOLUBLEINSOLUBLE

INSOLUBLE

SOLUBLE

SOLUBLE

INSOLUBLEINSOLUBLE

INSOLUBLEINSOLUBLEINSOLUBLE

INSOLUBLE

SOLUBLE

SOLUBLE

INSOLUBLEINSOLUBLE

SOLUBLESOLUBLESOLUBLE

SOLUBLE

INSOLUBLE

INSOLUBLE

SOLUBLESOLUBLE

S/SOLUBLES/SOLUBLES/SOLUBLE

S/SOLUBLE

S/SOLUBLE

S/SOLUBLE

S/SOLUBLES/SOLUBLE

Immiscible Two liquids that are insoluble (Oil & Vinegar)

Miscible Two liquids that are soluble in each other (Alcohol & Water)

VOCABULARY

SOLVENT WATER KEROSENE ACETONE ALCOHOL

Oil IMMISCIBLE MISCIBLE MISCIBLE S/MISCIBLE

Saturated solutionSolvent holds as much

solute as is possible at that temperature.

Undissolved solid remains in flask.

Dissolved solute is in dynamic equilibrium with solid solute particles.

Degree of Saturation

Unsaturated SolutionLess than the

maximum amount of solute for that temperature is dissolved in the solvent.

No solid remains in flask.


Supersaturated Solvent holds more solute than is normally possible at that

temperature.These solutions are unstable; crystallization can often be

stimulated by adding a “seed crystal” or scratching the side of the flask.


SOLUBILITYFACTORS AFFECTING

Factors Affecting Solubility

• Chemists use the axiom

• “like dissolves like”Polar substances

tend to dissolve in polar solvents.

Nonpolar substances tend to dissolve in nonpolar solvents.

LABORATORY ACTIVITY 2.8FACTORS SOLUBILITY

SOLVENT NaCl C12H22O11 C10H8 I2

Water

SOLVENT WATER KEROSENE ACETONE ALCOHOL

Oil IMMISCIBLE MISCIBLE MISCIBLE S/MISCIBLE

SOLUBLE SOLUBLE INSOLUBLE INSOLUBLE

TemperatureGenerally, the solubility of solid solutes in liquid solvents increases with increasing temperature.


SOLUTE COLD WATER

HOT WATER

TIME TO DISSOLVE

Salt

Sugar

KNO3

TAKES TIME TO DISSOLVE

EASILYDISSOLVED



EASILYDISSOLVED

EASILYDISSOLVED

TemperatureThe opposite is true

of gases. • Higher temperature

drives gases out of solution.Carbonated soft drinks

are more “bubbly” if stored in the refrigerator.

Warm lakes have less O2 dissolved in them than cool lakes.

Molecular Size The larger the molecules of the solute are, the larger is their molecular

weight and their size. It is more difficult it is for solvent molecules to surround bigger

molecules. If all of the above mentioned factors all excluded, a general rule can be

found that larger particles are generally less soluble. If the pressure, and temperature are the same than out of two solutes of

the same polarity, the one with smaller particles is usually more soluble.


SOLVENT REFINED SALT ROCK SALT

Water

SOLVENT REFINED KNO3 KNO3 CRYSTALS

Water


EASILYDISSOLVED


EASILYDISSOLVED

Effect of Stirring

Stirring only increases the speed of the process - it increases the movement of the solvent that exposes solute , thus enabling solubility.

As molecules in liquid substances are in constant move, the process would take place anyway, but it would take more time.


SOLUTE SET-UP W/ STIRRING

UNDISTURBED SET-UP

TIME TO DISSOLVE

CuSO4

KNO3

DISSOLVESFASTER

DISSOLVESFASTER

TAKES TIMEDISSOLVES

TAKES TIMEDISSOLVES


The stronger the intermolecular attractions between solute and solvent, the more likely the solute will dissolve.

Example: ethanol in waterEthanol = CH3CH2OH

Intermolecular forces = H-bonds; dipole-dipole; dispersion

Ions in water also have ion-dipole forces.


Glucose (which has hydrogen bonding)

is very soluble in water.

Cyclohexane (which only has dispersion forces)

is not water-soluble.


• Vitamin A is soluble in nonpolar compounds (like fats).

• Vitamin C is soluble in water.

Which vitamin is water soluble and which is fat soluble?

HEALTH APPLICATION

Gases in Solution

• In general, the solubility of gases in water increases with increasing mass.

Why?• Larger molecules

have stronger dispersion forces.

Gases in Solution• The solubility of

liquids and solids does not change appreciably with pressure.

• But, the solubility of a gas in a liquid is directly proportional to its pressure.

Increasing pressure

above solution forces

more gas to

dissolve.

Henry’s LawStates that:

Henry’s LawSg = 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.

Chemistry of solutions

Education

Transcript of Chemistry of solutions