CHAPTER 12 Page 1. Terms describing how liquids mix miscible: substances that are soluble in each other in any proportion.

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1 CHAPTER 12 Page 1 Slutins A slutin is a hmgeneus mixture The cmpnents f a slutin are: slute: substance (r substances) present in lesser amunt being disslved slvent: substance present in greater amunt ding the disslving state f slutin state f slvent state f slute example gas gas gas air liquid liquid gas xygen in water liquid liquid liquid alchl in water liquid liquid slid salt in water slid slid gas hydrgen in platinum slid slid liquid mercury in silver slid slid slid silver in gld (allys) Terms describing hw liquids mix miscible: substances that are sluble in each ther in any prprtin. immiscible: substances that d nt mix, frms tw layers ` Types f slutins slubility: max. amunt f slute that will disslve in a given amunt f slvent at a specific temperature. 1) saturated slutin cntains the maximum amunt f slute in a given slvent at a specific temperature. a slutin in equilibrium with undisslved slute 2) unsaturated slutin cntains less slute than it has the capacity t disslve a slutin nt in equilibrium with disslved slute mre slute can be disslved 3) supersaturated slutin cntains mre slute than is present in a saturated slutin unstable slutin prep: heat slutin t high temperature, then slwly cl

2 CHAPTER 12 Page 2 Explaining Slubility Slubility depends n 1) natural tendency fr slute and slvent t mix 2) tendency fr system t have lwest energy pssible "Like disslves like" i.e.: substances with similar IMF tend t disslve in ne anther nnplar slutes disslve in nnplar slvents (IMF: Lndn frces) plar & inic slutes are sluble in plar slvents macrmlecules are nt sluble in either plar r nnplar slvents Mlecular slutins "like disslves like" nnplar slutes with nnplar slvents: mixing and Lndn dispersin frces plar slutes with plar slvents mixing and diple/diple interactins Inic slutins inic cmpund with plar slvent energy f attractin between an in and water (in-diple frce) attractin f ins fr water mlecules (hydratin) must be strnger that the attractin fr in in the crystal (lattice energy)

3 CHAPTER 12 Page 3 Effects n Slubility Temperature 1) slid in water in mst cases (nt all) slubility f slid as temp examples f exceptins where slubility with a temp CaSO 4, Ca(OH) 2, Ce 2 (SeO 4 ) 3 2) gas in water slubility f gas as temp Pressure 1) Slid and liquid: Nt much effect with pressure 2) Gases are greatly affected by pressure Relatinship between gas slubility and pressure Henry's Law: slubility f a gas in a liquid is directly prprtinal t the partial pressure f a gas ver the slutin S = k H P S - slubility P - partial pressure f gas k H - Henry's Law cnstant fr a given gas & temperature system at equilibrium partial pressure f gas - mre mlecules will disslve in liquid why? mre mlecules are striking the surface f the liquid

4 CHAPTER 12 Page 4 Types f Cncentratin Units Cncentratin - amunt f slute present in a given amunt f slutin (slutin) 1) Mlarity (M) Mlarity = mles f slute liters f sl n units f ml/l 2) Mlality (m) number f mles f slute disslved in 1 kg f slvent mlarity = ml f slute kg f slvent 3) Mle Fractin (χ, greek symbl chi) mle fractin f cmpnent A = χ A = ml f A ttal ml f sl n ttal ml f slutin = ml slute + ml slvent 4) Percent Cncentratin (*nt in text) a) mass percentage f slute mass % f slute = mass slute mass sl n 100 *b) vlume percentage f slute vlume % f slute = vlume slute vlume sl n 100 *c) mass t vlume percentage f slute (g/ml) mass t vlume % f slute = mass slute vlume sl n 100

5 CHAPTER 12 Page 5 Cmparisn f Cncentratin Units mlarity easier t measure vlume f slutin, than t weigh slutin mlality independent f temperature (vlume f slutin usually with temp.) ml fractin gd fr calculatins f partial pressures f gas dealing with vapr pressures f slutins percent by mass independent f temperature d nt need t knw mlar mass f slute

6 CHAPTER 12 Page 6 Examples using varius Cncentratin Units: 1) An experiment calls fr 35.0 g f hydrchlric acid slutin that is 20.2% HCl by mass. a) Hw many grams f HCl is in this slutin? b) Hw many grams f water? given: slutin cnc. given in % mass 20.2% HCl = 35.0 g f HCl slutin g HCl 1 g sl n a) 35.0 g HCl sl n g HCl = 7.07 g HCl 1 g sl n b) g slutin = g slvent + g slute g H 2 O = g slutin - g HCl = 35.0 g slutin g HCl = 27.9 g H 2 O 2) What mass f glucse (C 6 H 12 O 6 ) must be disslved in 563 g ethanl (C 2 H 5 OH) t prepare a 2.40 x 10 2 m slutin? 3) Hydrgen perxide is a pwerful xidizing agent that is used in cncentrated slutin in rcket fuel systems and in dilute slutin as a hair bleach. an aqueus slutin f H 2 O 2 is 30.0% by mass and has a density f 1.11 g/ml. Calculates its a) mlarity b) mlality c) mle fractin f H 2 O 2

7 CHAPTER 12 Page 7 Clligative Prperties 1) Vapr Pressure Lwering 2) Biling Pt Elevatin P = ip χ A B T b = ik b 3) Freezing Pt Depressin T f = ik f 4) Osmtic Pressure Π = imrt Clligative Prperties depend n number f slute particles NOT the nature f the slute particles particles are atms, ins r mlecules i - van't Hff factr shw the number f particles a substance prduces in slutin i.e. Substance Particles in Slutin van't Hff factr C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq) i = 1 H glucse 2 O nnelectrlyte H 2 O NaCl (s) Na + (aq) + Cl (aq) i = 2 H 2 O Mg(NO 3 ) 2 (s) Mg 2+ (aq) + 2 NO 3 (aq) i = 3

8 CHAPTER 12 Page 8 1) Vapr Pressure (v.p.) Lwering a) If a nnvlatile slute is present in slutin, the vapr pressure f the slutin is always less than pure slvent (less slvent at the surface f the slutin t escape int the vapr phase) b) The relatinship between slutin vapr pressure and slvent vapr pressure depends n cncentratin f slute in slutin pure slvent slutin vapr pressure lwering P = ip A χ B P - P A P A P A - partial pressure f pure slvent χ B - ml fractin f slute Nte: vapr pressure lwering is directly prprtinal t χ B Vapr pressure lwering can be derived frm Rault's Law P A = P A χ A partial pressure f a slvent ver a slutin, P A, is given by vapr pressure f pure slvent P A times ml fractin f slvent in the slutin, χ A if slutin cntains ne slute: χ A + χ B = 1 substitute int Rault's law: distribute P A : χ A = (1- χ B ) P A = P A (1 χ B) slve fr P A χ B : P A = P A P A χ B simplify: P A χ B = P A P A vapr pressure lwering equatin: P A χ B = P Example f vapr pressure lwering: Eugenl, C 10 H 12 O 2 is the chief cnstituent f il f clve. It is a pale yellw liquid that disslves in ethanl, C 2 H 5 OH; it has a bp f 255 C (relatively lw vapr pressure). What is the vapr pressure lwering at 20.0 C f ethanl cntaining 8.56 g f eugenl in 50.0 g f ethanl? The vapr pressure f ethanl at 20.0 C is 4.6 mmhg.

9 CHAPTER 12 Page 9 2) Biling pint (bp) elevatin a) nnvlatile slute lwers vapr pressure f the slutin which als affects biling pint f the slutin b) recall: biling pint - temperature at which vapr pressure f slutin equals external atmspheric pressure Pressure 1 atm The slid line represents phase bundaries fr the pure slvent and the dtted line represents phase bundaries fr the slutin. The nrmal freezing pint (fp) and biling pint (bp) f the pure slvent and the slutin are shwn by the dts. At 1 atm pressure the bp f the slutin is higher than the pure slvent. fp sl'n fp pure slvent bp sl'n bp pure slvent Temperature bp elevatin T b T b = T b T b T b = i k b : : T b - bp slutin; - bp pure slvent T b i - van't Hff factr k b - bp elevatin cnstant (depends n slvent) - mlality cncentratin

10 CHAPTER 12 Page 10 3) Freezing pint (fp) depressin usually pure slvent freezes ut f slutin Pressure 1 atm The slid line represents phase bundaries fr the pure slvent and the dtted line represents phase bundaries fr the slutin. The nrmal freezing pint (fp) and biling pint (bp) f the pure slvent and the slutin are shwn by the dts. At 1 atm pressure the fp f the slutin is lwer than the pure slvent. fp sl'n fp pure slvent bp sl'n bp pure slvent Temperature fp depressin T f T f = T f T f : T f - fp slutin; - fp pure slvent T f T f = i k f : i - van't Hff factr k f - fp elevatin cnstant (depends n slvent) - mlality cncentratin Nte: slute must be nnvlatile fr bp elevatin; N restrictin fr fp depressin Ethylene glycl (EG) CH 2 OHCH 2 OH, is a cmmn autmbile antifreeze. It is water sluble and fairly nnvlatile (bp = 197 C). Calculate the freezing pt. f a slutin cntaining 651 g f EG in 2505 g f water. Wuld yu keep this substance in yur car during the summer? (EG, M m = g/ml)

11 CHAPTER 12 Page 11 Determining Mlar mass frm bp elevatin r fp depressin experiments Derive an equatin relating bp t the M m f slute bp elevatin equatin. define sub int bp elevatin equatin. T b = ik b = ml slute kg slvent T b = ik b (ml slute) (kg slvent) define ml slute ml slute = g slute M m slute sub ml slute ik b (g slute) T b = (kg slvent)(m m slute) rearrange and slve fr M m M m = ik b (g slute) T b (kg slvent) Example: An 11.2 g sample f sulfur was disslved in 40.0 g f carbn disulfide (CS 2 ). the bp elevatin f CS 2 was fund t be 2.63 C. What is the M m f the sulfur in slutin? What is the frmula f mlecular sulfur?

12 CHAPTER 12 Page 12 4) Osmtic pressure (Π) Osmsis is the net mvement f slvent mlecules thrugh a semipermeable membrane frm a pure slvent r frm a dilute slutin t a mre cncentrated slutin. semipermeable membrane - allws slvent mlecules t pass thrugh but blcks passage f slute mlecules. wait sme time Π semipermeable membrane Osmtic pressure pressure required t stp smsis Π = imrt M - mlar cncentratin R - gas law cnstant = L-atm/ml-K T - abslute temperature i - van't Hff factr Osmsis an imprtant bilgical prcess A cell is an aqueus slutin surrunded by semipermeable membrane and utside the membrane is an aqueus slutin If a slutin has the same smtic pressure as then cell, the slutin is istnic If the slutin has a greater smtic pressure than the cell, the slutin is hypertnic If the slutin has a smaller smtic pressure than the cell, the slutin is hyptnic If a cell is place in a hypertnic slutin, the slvent flws ut f cell and the cell shrinks crenatin hyptnic slutin, the slvent flws int the cell and the cell swells and burst hemlysis

13 Cllids CHAPTER 12 Page 13 Dispersin f particle f ne substance thrughut anther substance Dividing line between slutins and hetergeneus mixtures Dispersed particles are larger than mlecules in a slutin but nt s large that the cmpunds f the mixture separate under the influence f gravity Examples: Fg, smke, whipped cream, milk, paint, marshmallw, butter, ruby glass Particle size: 10Å t 2000Å (can nt see withut micrscpe) Particles are large enugh t scatter light Tyndall effect - scattering f light by cllidal particles Types f Cllids aersls - liquid drplets (fg) r slid particles dispersed thrughut a gas emulsin - liquid drplets dispersed thrughut anther liquid (milk) sl - slid particles dispersed in a liquid (bilgical fluids) fam - gas in a liquid r slid (whipping cream) Tw majr classes f cllids 1) hydrphilic cllid water-lving strng attractin between dispersed phase and water 2) hydrphbic cllid water-hating lack f attractin between dispersed phase and water unstable, aggregates int larger particles Cagulatin - prcess by which dispersed phase f a cllid is made t aggregate and separate frm the cntinus phase examples f cagulatin curdling f milk - lactse ferments t lactic acid delta frmatin - sil in river water meets cncentrated inic slutin in the cean Cllids can have bth majr classes present in ne substance ne end is hydrphilic and the ther end is hydrphbic in water the hydrphbic ends assciate tgether while the hydrphilic ends assciate with water mlecules. This prcess is knwn as frming micelles micelles - a cllidal-sized particle frmed in water by the assciatin f mlecules r ins that have a hydrphbic end and a hydrphilic end. Saps are cllids which frm micelles- refer t yur text bk