Chapter 13

13.1 What is a solution?• mixture

– two or more subs. that are physically combined

– no form./any proportion– subs. 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 – a two phase heterogeneous mixture that separates upon standing

• particles are >1000 nm in size

– clay in water– dust in air

• colloid – a two phase heterogeneous mixture that remains mixed(usually due to like charged particles)

• 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

• 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

13.2 Concentration and Molarity

• 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 to kilograms 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) volume % (%v/v)– volume solute per volume solution

13.3 Solubility and the Dissolving Process

• solubility – the 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

• dissolving– the breaking up of a solute to the smallest

particles that make up the solute• particles 0.1 to 2 nm• NaCl breaks apart to Na+ & Cl- ions• sugar break apart to C12H22O11 molecules

– occurs at surface of solute– methods utilized to increase dissolving rate of

a solid in a liquid• powdering/crushing

– more surface area

• stirring– fresh solvent in contact with solute

• heating

• 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– increasing temp. increases dissolving– temp. of solution decreases during dissolving– temp. of solution increases during crystallizing

• cold pack• most solutes

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

• heating decreases dissolving

– not very common• NaOH

• solubility of ionic compounds– vary due to many factors

• soluble – more than 1 g/100 g H2O

• slightly soluble – 0.1 to 1 g/100 g H2O

• insoluble – less than 0.1 g/100 g H2O

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

• if dissolving and crystallizing are at equilibrium– amount of undissolved solute remains

constant– saturated solution – solvent is “holding” the

maximum amount of solute at those conditions

– saturated solutions contain undissolved solute

• if dissolving is occurring faster than crystallizing– no undissolved solute– all solute dissolves– unsaturated solution – solvent is holding less

than the maximum amount of solute• dissolving > crystallizing• each substance has different solubility @ different

temperatures– solubility curve – figure 12, page 472

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

of solute @ the specified conditions• more solute than a saturated solution

– not common– very easily disturbed

• honey• liquid hand warmers

• 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