As size , rate

As To , rate

3. mixing

Factors Affecting Solubility

1. temperature

2. particle size

4. nature of solvent/solute (“like dissolves like”, polar dissolves polar)

More mixing, rate

Measuring Concentration

Concentration…a measure of solute-to-solvent ratio

concentrated vs. dilute“lots of solute” “not much solute”

“watery”

Add water to dilute a solution; boil water off to concentrate it.

Measuring Concentration“The amount of solute in a solution”

mol

L M

A. Parts per million (ppm) also, ppb and ppt = g solute/1,000,000 g solution

– commonly used for minerals or contaminants in water supplies

B. Molarity (M) = moles of solute L of solution – used most often

C. Molality (m) = moles of solutekg of solvent

One mole, in solution.

Molarity

solution of Lsolute of moles(M)molarity

liter of solutionL 1mol0.25 0.25m

Molarity

Find the molarity of a solution containing 75 g of MgCl2 in 250 ml of water.

75 g MgCl2 1 mol MgCl2

95.21 g MgCl2

= 3.2M MgCl2

0.25 L water

LmolM

Molality

solvent ofkg solute of moles(m)molality

mass of solvent only

1 kg water = 1 L waterkg 1mol0.25 0.25m

Molality

Find the molality of a solution containing 75 g of MgCl2 in 250 ml of water.

75 g MgCl2 1 mol MgCl2

95.21 g MgCl2

= 3.2m MgCl2

0.25 kg water

kgmolm

Molality

How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water?

0.500 kg water 1.54 mol NaCl

1 kg water

= 45.0 g NaCl

58.44 g NaCl

1 mol NaCl

kg 1mol1.5 1.5m

As size , rate

As To , rate

3. mixing

Factors Affecting Solubility

1. temperature

2. particle size

4. nature of solvent/solute (“like dissolves like”, polar dissolves polar)

More mixing, rate

Solubility (“Dissolution”)

• Temperature-The solubility of most solids in water increases as the temperature of the sol’n increases.

-The solubility of gases in water decreases with increasing temperature

Solubility (“Dissolution”)

Water

HOT

A B

AFTERBefore

Water

COLD

Water

HOT

Add 1 drop of red food coloring

Miscible – “mixable”

two gases or two liquids that mix evenly

Experiment 1:

Water

COLD

A B

Solubility (“Dissolution”)

Water Water

Oil

T30 sec

AFTERBefore

Add oil to water and shake

Immiscible – “does not mix”

two liquids or two gases that DO NOT MIX

Experiment 2:

T0 sec

Gas Solubility

CH4

O2

CO

He

Temperature (oC)

Sol

ubili

ty

2.0

1.0

0 10 20 30 40 50

Higher Temperature

…Gas is LESS Soluble

Solubility: forming a “saturated” solution in equilibrium

SATURATED SOLUTION

no more solute dissolves

UNSATURATED SOLUTIONmore solute

dissolves

SUPERSATURATED SOLUTION

becomes unstable, crystals form

increasing concentration

“Oil and Water Don’t Mix”

• Oil is nonpolar• Water is polar

“Like dissolves like”, nonpolar dissolves nonpolar, nonpolar does not dissolve polar

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 470

O2-

H+

H+H2O

++

Water MoleculeWater is a POLAR molecule

Dissolving of NaCl in Water

NaCl(s) + H2O Na+(aq) + Cl-(aq)

Cl-ions

Na+

ions Water molecules

O

H

Ethanol is Polar

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 469

C C

H

H

H

H

H

-

+

Polar bond

Ethanol and Water are Soluble

‘Like dissolves like’

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 469

O

H C C

H

H

H

H

H

O

H

H

Cleaning Action of Soap

Micelle

Timberlake, Chemistry 7th Edition, page 573

MODEL OF A SOAP MOLECULE

NONPOLARHYDROCARBON

TAIL

POLARHEAD

Na1+

emulsifying agent (emulsifier): -- molecules w/both a polar AND a nonpolar end-- allows polar and nonpolar substances to mix

detergent lecithin eggse.g., soap

Interstitial Spaces

Water Water Water Water Water Water WaterWaterdissolveddissolved

solidsolid

Oil Oil Oil Oil Oil Oil Oil

red foodred foodcoloringcoloring

Layer

Non-polar

Polar

"immiscible"

Water Water Water Water Water Water WaterWater

Clogged Pipes – Hard Water

‘hard’ water

carbonic acid

Step 1: Acid rain is formed

Step 2: Acid rain dissolves limestone

Water softner

H2O + CO2 H2CO3

H2CO3 + CaCO3 Ca(HCO3)2

H2CO3 + MgCO3 Mg(HCO3)2

Pipes develop ScalesStep 3: Hard water is heated and deposits scales

Ca(HCO3)2 CaCO3(s) + H2O + CO2

Mg(HCO3)2 MgCO3(s) + H2O + CO2

scales on pipes

Water PurificationHardWater

CationExchanger

AnionExchanger

DeionizedWater

(a) (b) (c)

H+

H+

H+

H+

H+

H+

H+

H+

OH-

OH-

OH-

OH-

OH-

OH-

OH-

OH-

(a) The cations in hard water are exchanged for H+.(b) The anions in hard water are exchanged for OH-.(c) The H+ and OH- combine to give H2O.

Hard water is softened by exchanging Na+ for Ca2+, Mg2+, and Fe3+.

Corwin, Introductory Chemistry 2005, page 361

Na+

Ca2+

Mg2+

Fe3+

Pure water does not conduct an electric current

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215

Source ofelectric power

Purewater

Ionic Solutions conduct a Current

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 215

Source ofelectric power

Free ionspresent in water

electrolytes: solutes that dissociate in solution-- conduct electric current because of free-moving ions e.g., acids, bases, most ionic compounds-- are crucial for many cellular processes-- obtained in a healthy diet-- For sustained exercise or a bout of the flu, sports drinks

ensure adequate electrolytes.

nonelectrolytes: solutes that DO NOT dissociate-- DO NOT conduct electric current (not enough ions) e.g., any type of sugar

NaCl Na1+ + Cl1–

CH3COOH CH3COO1– + H1+

Weak electrolytes exhibit little dissociation.

“Strong” or “weak” is a property of the substance.We can’t change one into the other.

Strong electrolytes exhibit nearly 100% dissociation.

NOT in water: 1000 0 0in aq. solution: 1 999 999

NOT in water: 1000 0 0in aq. solution: 980 20 20

Electrolytes

Timberlake, Chemistry 7th Edition, page 290

ElectrolytesElectrolytes - solutions that carry an electric current

NaCl(aq) Na+ + Cl- HF(aq) H+ + F-

strong electrolyte weak electrolyte nonelectrolyte

…normal boiling point (NBP) …higher BP

FREEZING PT.DEPRESSION

BOILING PT.ELEVATION

Colligative Properties depend on concentration of a solution

Compared to solvent’s… a solution w/that solvent has a……normal freezing point (NFP) …lower FP

1. salting roads in winter

FP BP

water 0oC (NFP) 100oC (NBP)

2. antifreeze (AF) /coolant

FP BP

water 0oC (NFP) 100oC (NBP)

water + a little AF –10oC 110oC

50% water + 50% AF –35oC 130oC

water + a little saltwater + more salt

–11oC 103oC–18oC 105oC

Applications (NOTE: Data are fictitious.)

Effect of Pressure on Boiling PointBoiling Point of Water at Various Locations

LocationLocationFeet Feet

above above sea levelsea level

PPatm atm (kPa)(kPa)Boiling Boiling Point Point ((C)C)

Top of Mt. Everest, Tibet 29,028 32 70

Top of Mt. Denali, Alaska 20,320 45.3 79

Top of Mt. Whitney, California 14,494 57.3 85

Leadville, Colorado 10,150 68 89

Top of Mt. Washington, N.H. 6,293 78.6 93

Boulder, Colorado 5,430 81.3 94

Madison, Wisconsin 900 97.3 99

New York City, New York 10 101.3 100

Death Valley, California -282 102.6 100.3