Chapter 12

12.1 What is a solution?• mixture

– two or more subs. physically combined– no formula, any proportion– retain properties– easily separated by physical means

• solution – homogeneous mixture– solute – subs. being dissolved(sugar)

• particles are 0.1 to 2 nm in size

– solvent – subs. doing the dissolving(water)

Solution Solute Solventsalt water salt(s) water(l)

radiator fluid antifreeze(l) water(l)

pop/cola CO2 (g) water(l)

dental filling Hg (l) Ag, Sn, Cu (s)

brass Cu (s) Zn (s)

filter on gas mask poisonous gas(g) charcoal(s)

air O2 (g) N2 (g)

????? ??? (l) ??? (g)

????? ??? (s) ??? (g)

• suspension – two phase heterogeneous mixture – separates

• particles are >1000 nm in size• clay in water• dust in air

• colloid – two phase heterogeneous mixture– remain mixed(usually due to like charged

particles)– emulsion/foam

• particles are 2 to 1000 nm in size• milk – fat and casein dispersed in whey• glue water – glue dispersed in water

• Tyndall effect – scattering of light caused by undissolved particles– gaseous or liquid solutions = dissolved - no

Tyndall effect– suspensions or colloids = undissolved –

positive for Tyndall effect

laser light show link

• separation techniques for mixtures– filter/decant - colloids and

suspensions

– evaporation – remove liquids from solids

– chromatography – separates solutions by molecular size

– distillation – separates solutions by boiling• fractional distillation – separation by boiling point

differences

• electrolyte– substance that when dissolved or molten

conducts electricity• carry e-‘s• ions need to be present• ionic compounds dissociate when dissolved

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

• acid ionizationHCl(l) H+(aq) + Cl-(aq)

– What are the electrolytes in Gatorade?– In Gatorade, the key electrolytes are the minerals

sodium, potassium and chloride. When athletes sweat, they lose electrolytes such as sodium, potassium, and chloride that are essential to hydration and muscle function. Unlike water and other beverages that are not scientifically formulated, Gatorade is lab-tested to ensure it helps replenish the electrolytes lost in sweat and stimulates thirst so athletes will ingest an adequate amount of fluid and electrolytes to stay better well-hydrated compared to when using beverages without electrolytes, particularly sodium.¹²³

http://www.gatorade.com/frequently_asked_questions/default.aspx

• strong electrolyte– completely ionize/dissociate– lots of ions

10 NaCl(s) 10 Na+(aq)+ 10 Cl-(aq)• weak electrolyte

– partially ionize/dissociate– few ions10 HC2H3O2(l) H+(aq) + C2H3O2

-(aq) + 9 HC2H3O2(aq)

• nonelectrolyte– no ionization/dissociation– no ions– molecules(not acids)

12.2 The Solution Process• solubility – ability of a subs. to dissolve @

specific T and P conditions– hydrophilic

• “water loving”• dissolve in water• vitamin C• most ionic compounds• polar molecules

– hydrophobic• “water fearing”• insoluble in water• soluble in fats or oils

– vitamin A– wax– styrofoam

• general rule of solubility– “like dissolves like”– soaps/detergents dissolve in both

• polar end of soap – attaches to water• nonpolar end of soap – attaches to dirt/oil/fat

– miscible – mutually soluble– immiscible – does not dissolve

laundry ball

• surfactants – substance that concentrates at the interface between two phases– solid-liquid, liquid-liquid, liquid-gas– detergent – synthetic surfactant(not natural)

• generally made from vegetable oil and sulfuric acid• often liquid

– soap – natural surfactant• generally made from sodium/potassium salts of

natural animal fatty acids• often solid

– emulsifying agent - substance, such as soap or eggs, that allows two immiscible liquids to remain dispersed in one another

• Sodium Lauryl Sulfate – SLS – An Industrial Detergent

• SLS is an Engine Degreaser! And it’s in nearly every cleansing product we use from toothpaste to beauty soap. SLS is generally made from petroleum oil and sulfuric acid, and may still contain traces of both. It makes personal products foamy, and is a strong detergent that strips away the skin’s precious oils in addition to removing dirt. Ironically, the FDA actually uses it as a skin irritant to test the anti-irritation properties of various drugs.

• Sodium Laureth Sulfate• Sodium Laureth Sulfate (SLES) is one of the most common shampoo

ingredients. In fact most personal hygiene products contain this specific ingredient. SLES is a washing surfactant, in other words a washing detergent. Imagine it as a car polish that returns the shine by removing the top layer of the paint.

• dissolving– breaking up of solute into the smallest particles that

make up the solute• ionic compounds -- NaCl Na+ & Cl- ions• molecules -- sugar C12H22O11 molecules

– occurs at surface of solute (simulation)– methods to increase dissolving rate of a solid in a

liquid• powdering/crushing

– more surface area

• stirring/agitating– fresh solvent in contact with solute

• heating– helps separate solute molecules

• dissolving mechanisms and NRG changes1) solute(s) solute(l)

• NRG is added to solute for phase change• dissociation – separation in to ions/molecules• endothermic

2) solvent moves apart to allow solute to enter• solvent makes room for solute• NRG needed to move solvent apart• endothermic

3) solute and solvent attract• solvation/hydration• decrease entropy – release NRG• exothermic

• if dissolv. mech. 1 & 2 > 3– dissolving is endothermic– heating increases dissolving– solution feels cold during dissolving– temp. of solution increases during crystallizing

• cold pack• most solutes

• if dissolv. mech. 1 & 2 < 3– dissolving exothermic– heating decreases dissolving

• cooling increases dissolving

– not very common• NaOH

• equilibrium – two opposing processes occurring simultaneously– melting/freezing– dissolving/crystallizing

• if a solution is at equilibrium– undissolved solute remains in solvent

• crystals in bottom of container

– saturated solution – solvent “holding” maximum amount of solute at those conditions

• if dissolving is occurring faster than crystallizing(not at equillibrium)– no undissolved solute– all solute dissolves– unsaturated solution – solvent holding less

than maximum amount of solute• dissolving > crystallizing

• supersaturated solution– unique phenomena– solvent holds more than maximum amount of

solute @ specified conditions• more solute than saturated solution

– not common– very easily disturbed

• honey• liquid hand warmers• video, video2, video3

• solubility of gases in liquids– different than solids/liquids– T affect solubility of gases

• solubility increases as T of solvent decreases– less molecular motion– gas particles remain isolated– cold liquids dissolve more gases

» cloudy ice– hot liquids dissolve less gases

» thermal pollution

– P affect solubility• Henry’s law

– solubility of a gas in a liquid is directly related to the P of that gas above the liquid

– fizz keeper

12.3 Concentration of Solutions

• concentration – the ratio of solute to solvent– qualitative

• dilute• concentrate

• quantitative1) parts per million(ppm)

• # of solute particles to solution particles• 1 ppm = 1 solute particle to 1,000,000 total

particles• 1 drop of food coloring in 40 gal H2O

• for aqueous solutions = mg solute/L solution

What is the concentration in ppm for a solution that has 0.0380 grams of lead in 300.0 mL of tap water solution?

X ppm = 1000 mg x 0.0380 g Pb x 1000 mL

1 g x 300.0 mL sol x 1L

X ppm = 127 mg/L or ppm

http://planetforlife.com/co2history/index.html

• Atmospheric carbon dioxide during the last four ice ages.

(http://planetforlife.com/co2history/index.html)

2) parts per billion(ppb)– micrograms/L (µg/L)– 1 ppb =

• 1 mL of water in an Olympic swimming pool• 7 people in the world at current population

• Sixteen pesticides have been detected in eight brand-name baby foods, according to a study by the Environmental Working Group and the National Campaign for Pesticide Policy Reform, two public interest groups based in Washington, DC.

• In their study, the EWG and the NCPPR collected a random sampling of 76 jars of baby food from grocery store shelves in Denver, Philadelphia, and San Francisco. The group chose fruits and vegetables babies most commonly eat during their first year of life. Of these, 53% harbored traces of one pesticide, and 18% had two or more pesticides. Plums contained the highest amounts at 46 parts per billion and peaches contained 29 parts per billion. Pears had the highest number of multiple pesticides overall (five).

3) molarity(M)• # of particles to volume of solution• M = mol solute/L solution

– vinegar is composed of 5.00 grams of acetic acid(HC2H3O2) in 100.0 mL of solution. What is the M of vinegar?

M = 1 mole acetic acid x 5.00 g acetic acid

60.06 g acetic acid x 0.1000 L solution

M = 0.833 mol/L or M

4) molality (m)– # particles solute to mass solvent– moles of solute per kilogram of solvent

• used in calculating freezing point depressions and boiling point elevations

5) karat (k)– concentration of Au in alloys

• 24 k gold = pure Au• 12 k gold = 50% Au & 50% other metal(s)

6) mass % (% m/m)– mass of solute per mass solution– used in industry

In a regular Coke there is 39 grams of sugar in 355 grams of pop, what is mass %?

% m/m = 39 grams sugar/355 grams pop

% m/m = 11% sugar

7) %(m/v)– mass of solute(g) per volume solution(mL)– typically used for unsaturated solutions and

medicine– saline solution = 0.90%(m/v)

Chapter 13 Colligative Properties

13.2 Colligative Properties of Solutions– any prop. that affects the solvents physical prop.

because of the number of solute particles– adding solute to solvent changes the prop. of

the solvent

1) vapor pressure • decreases when solute is added to solvent• vapor P = P created when a confined liquid evap.• less solvent part. at surface to evap.

– less evap. = less P– tap water evap. slower than distilled water– sim lab

2) freezing point – decreases when solute is added to solvent– freezing pt.(tf) – temp. at which the vapor P

of the solid = vapor P of liquid– since vapor P of liquid is reduced, tf is

reduced– solutions freeze at lower temp. than pure

solvents• more solute particles = lower freezing points

• (simulated lab)

• freezing pt. depression calculationΔtf = m x Kf x i

m = molality(mol solute/kg solvent)

Kf = freezing pt constant(water = 1.86o C/m)

i = van’t Hoff factor = # particles dissoc./ionized

• freezing pt depression sample problem– What temp. does 175 grams of water freeze if

22.5 grams of sodium chloride is added?

Δtf = m x Kf x i

Δtf = 1 mol NaCl x 22.5 g NaCl x 1.86o C x 2

58.44 g NaCl x 0.175 Kg H2O x m

Δtf = 8.18o C

normal tf = 0o C

- Δtf = 8.18o C

new tf = - 8.18o C

• How many grams of calcium chloride are needed to lower the freezing point of 750.0 grams of water to -6.55o C?

Δtf = 6.55o C

X m = 6.55o C____

1.86o C/m x 3

X m = 1.17 mX g CaCl2 = 110.98 g CaCl2 x 1.17 mol CaCl2 x 0.7500 Kg

1 mol CaCl2 x Kg

X g CaCl2 = 97.4 g CaCl2

3) boiling point – increases when solute is added to solvent• boiling point = temp. at which the vapor P of

the liquid is equal to atmospheric P• tb – H2O = 100o C @ 1 atm

• solute reduces vapor P of solvent• more NRG added to get same vapor P

• t of liquid will be higher to attain vapor P = atm. P

• solutions have higher boiling points than pure solvents

• more solute particles = higher boiling points

Δtb = m x Kb x i

m = molality

Kb = boiling point constant (H2O = 0.510o C/m)

i = van’t Hoff factor

My mom always adds salt to the water when she cooks noodles so the noodles cook faster. She adds about 2.0 grams of salt to 1.0 liter of water. What temp. does her water boil?

Δtb = 1 mol NaCl x 2.0 g NaCl x 0.510o C x 2

58.44 g NaCl x 1.0 Kg x m

Δtb = 0.035o C

normal tb = 100o C

+ Δtb = 0.035o C

new tb = 100.035o C

• How many grams of sugar(C12H22O11) would need to be added to 500.0 grams of water to increase the boiling point to 105.0o C?

Δtb = 5.0o C

X m = 5.0o C________

0.510o C/m x 1

X m = 9.8 m

X g = 342.34 g x 9.8 mol x 0.5000 Kg

1 mol x 1 Kg

X g = 1700 g sugar

– osmosis• movement of solvent through a semipermeable

membrane from lower solute conc. to higher solute conc.

http://chemed.chem.wisc.edu/chempaths/index.php?option=com_awiki&view=chemprime&Itemid=854&article=File:Osmosis.gif

• osmotic pressure– applied external pressure that stop osmosis– minimum pressure required to stop osmosis

• osmolarity– concentration of an osmotic solution– osmolarity(osmol/L or osM) = molarity(M) x i– what is osM of saline(sodium chloride)

solution(0.90%(m/v))?

• dialysis– the process of osmosis in most plant and

animal cells• solvent molecule, small solute molecules and ions

are allowed to pass thru the cell wall or membrane• artificial kidney machine

• isotonic solutions– solutions that have the same osmotic

pressure or same osmolarity– blood cells = 0.270 osmol to 0.300 osmol

• dialysing solution has same osmolarity/osmotic pressure as blood but with out the waste

• waste material passes thru semipermeable membrane/dialysis tubing

• IV fluids must have same osmolarity/osmotic pressure as blood

• hypertonic solution – solution with higher osmolarity or osmotic pressure– cell has lower conc. of solute than surrounding

solution• osmolarity solution > blood (0.30 osM)

– water moves out of cells, cells shrink(crenation)– salting foods kills bacteria cells

• hypotonic solution – solution with lower osmolarity or osmotic pressure– cell contains greater conc. of solute than

surrounding solution• osmolarity solution < blood(0.27 osM)

– water moves into cell, cells swell(hemolysis)

• reverse osmosis– process that exerts a pressure on the solvent

greater than osmotic pressure of solution– causes solvent to move from solution to

solvent side of semipermeable membrane

fractional distillation video