Chapter 13 Properties of Solutions

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1 화학 1 1 장물질과측정 2 장원자, 분자, 이온 3 장화학양론 4 장수용액반응 5 장열화학 6 장원자의전자구조 7 장원소의주기적성질 8 장화학결합 9 장분자의기하학적구조와결합이론 10 장기체 11 장액체와분자간힘 12 장고체및신소재 화학 2 13 장용액의성질 14 장화학반응속도론 15 장화학평형 16 장산 - 염기평형 17 장수용액평형의다른관점 18 장환경화학 19 장화학열역학 20 장전기화학 21 장핵화학 22 장비금속화학 23 장전이금속과배위화학 24 장생명의화학 : 유기화학과생화학

2 CHEMISTRY? 케미?

3 CAS [Chemical Abstract Service] 1907 년에설립되었으며현재는사실상전세계화학정보센터역할을하고있으며, 따라서 CAS 가작성하는화학정보데이터베이스는세계최대이다. 또 CAS 는세계의화학문헌을망라한 Chemical Abstracts 를발행하고있다. 보통화학상품에는 CAS 넘버 ( 번호 ) 가부여되고있다.

4 LPG 의주성분은프로페인이며프로페인은탄소를 3 개를가지는유기화합물 ( 탄화수소 ; C 3 H 8 ) 이다. 다음물음에답하시오. a) 가스버어너에서프로페인의연소반응식을쓰시오. b) a) 항에대해서화학양론을설명하시오. c) b) 항을이용하여프로페인 20L 를연소시켰을때발생하는이산화탄소는몇 L 인가?( 표준상태로가정하라 ) 또한이산화탄소의분자갯수는몇개인가? [ 단프로페인의비중 ( 밀도 ) 은 0.9, C;12, H;1] d) a) 항에서 H(kJ/mol) 를구하시오. [ 단 25 에서 propane 의 H f o = (kJ/mol), CO 2 의 H f o = (kJ/mol), H 2 O(l) 의 H f o = (kJ/mol)] e) 가정용 LP 가스탱크에는프로페인 (C 3 H 8 ) 1.32 x 10 3 g 들어있다. 그탱크속에있는모든프로페인이완전연소될때, 연관된열량 (kj) 을계산하라. 원자, 분자, 분자식, 원자량, 몰질량, 몰, 화학양론, 밀도, 기체법칙

5 Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 13 Properties of John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc.

6 are homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the solvent.

8 The intermolecular forces between solute and solvent particles must be strong enough to compete with those between solute particles and those between solvent particles.

9 How Does a Solution Form? As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates(hydrates), them.

10 How Does a Solution Form If an ionic salt is soluble in water, it is because the iondipole interactions are strong enough to overcome the lattice energy of the salt crystal.

11 Energy Changes in Solution Simply put, three processes affect the energetics of the process: Separation of solute particles Separation of solvent particles New interactions between solute and solvent

12 Energy Changes in Solution The enthalpy change of the overall process depends on H for each of these steps. MgSO 4 NH 4 NO 3

13 Enthalpy Is Only Part of the Picture The reason is that increasing the disorder or randomness (known as entropy) of a system tends to lower the energy of the system.

14 Enthalpy Is Only Part of the Picture So even though enthalpy may increase, the overall energy of the system can still decrease if the system becomes more disordered.

17 NiCl 2 (aq) NiCl 2 (s) Ni(s) + 2HCl(aq) NiCl 2 (aq) + H 2 (g)

18 CoCl 2 6H 2 O CoCl 2 NaCl solution NaCl( 소금 ) Δ

19 Types of Saturated Solvent holds as much solute as is possible at that temperature. Dissolved solute is in dynamic equilibrium with solid solute particles.

20 Types of Unsaturated Less than the maximum amount of solute for that temperature is dissolved in the solvent.

21 Types of Supersaturated Solvent holds more solute than is normally possible at that temperature. These solutions are unstable; crystallization can usually be stimulated by adding a seed crystal or scratching the side of the flask.

22 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.

23 Factors Affecting Solubility The more similar the intermolecular attractions, the more likely one substance is to be soluble in another.

24 Factors Affecting Solubility Glucose (which has hydrogen bonding) is very soluble in water, while cyclohexane (which only has dispersion forces) is not.

25 Factors Affecting Solubility Vitamin A is soluble in nonpolar compounds (like fats). Vitamin C is soluble in water.

26 Gases in Solution In general, the solubility of gases in water increases with increasing mass. Larger molecules have stronger dispersion forces.

27 Gases in Solution The solubility of liquids and solids does not change appreciably with pressure. The solubility of a gas in a liquid is directly proportional to its pressure.

28 Henry s Law where S g = kp g S g is the solubility of the gas; k is the Henry s law constant for that gas in that solvent; P g is the partial pressure of the gas above the liquid.

31 Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.

32 Temperature The opposite is true of gases: Carbonated soft drinks are more bubbly if stored in the refrigerator. Warm lakes have less O 2 dissolved in them than cool lakes.

33 Ways of Expressing Concentrations of

34 Mass Percentage Mass % of A = mass of A in solution total mass of solution 100

35 Parts per Million and Parts per Billion Parts per Million (ppm) ppm = mass of A in solution total mass of solution 106 Parts per Billion (ppb) ppb = mass of A in solution total mass of solution 109

36 Mole Fraction (X) X A = moles of A total moles in solution In some applications, one needs the mole fraction of solvent, not solute make sure you find the quantity you need!

37 Molarity (M) M = mol of solute L of solution You will recall this concentration measure from Chapter 4. Because volume is temperature dependent, molarity can change with temperature.

38 Molality (m) m = mol of solute kg of solvent Because both moles and mass do not change with temperature, molality (unlike molarity) is not temperature dependent.

39 Changing Molarity to Molality If we know the density of the solution, we can calculate the molality from the molarity, and vice versa.

Colligative Properties Changes in colligative

40 Colligative Properties Changes in colligative properties depend only on the number of solute particles present, not on the identity of the solute particles. Among colligative properties are Vapor pressure lowering Boiling point elevation Melting point depression Osmotic pressure

41 Vapor Pressure Because of solutesolvent intermolecular attraction, higher concentrations of nonvolatile solutes make it harder for solvent to escape to the vapor phase.

42 Vapor Pressure Therefore, the vapor pressure of a solution is lower than that of the pure solvent.

43 Raoult s Law where P A = X A P A X A is the mole fraction of compound A P A is the normal vapor pressure of A at that temperature NOTE: This is one of those times when you want to make sure you have the vapor pressure of the solvent.

44 Boiling Point Elevation and Freezing Point Depression Nonvolatile solutesolvent interactions also cause solutions to have higher boiling points and lower freezing points than the pure solvent.

45 Boiling Point Elevation The change in boiling point is proportional to the molality of the solution: T b = K b m T b is added to the normal boiling point of the solvent. where K b is the molal boiling point elevation constant, a property of the solvent.

46 어는점내림과끓는점오름 : 더낮은온도에서얼고더높은온도에서끓는물만들기 1.7 m 에틸렌글리콜용액의어는점을계산하라. 풀이 ) 주어진값 : 1.7 m 용액구하는값 : ΔT f o 계산식 : Ckg T = m K mol f = 1.7 용질용매 1.86 = 3. kg용매 mol용질 o f 2 실제어는점 = = -3.2 C 46

47 1.7 m 에틸렌글리콜용액의끓는점을계산하라. 풀이 ) 주어진값 : 1.7 m 용액구하는값 : 끓는점 o Ckg T m K mol f = f = 1.7 용질용매 = kg용매 mol용질 실제끓는점 = = o C 다음중어느용액이가장높은끓는점을가질것인가? (a) 0.50M C 12 H 22 O 11 (b) 0.50M C 6 H 12 O 6 (c) 0.50M C 2 H 6 O 2 (d) 이용액들모두같은끓는점을가질것이다. 풀이 ) (d) 끓는점오름은용해된입자의농도에만의존하고용해된입자의종류에는의존하지않기때문에, 이용액들모두같은끓는점을가질것이다. 47

48 Freezing Point Depression The change in freezing point can be found similarly: T f = K f m T f is subtracted from the normal freezing point of the solvent. Here K f is the molal freezing point depression constant of the solvent.

49 Boiling Point Elevation and Freezing Point Depression Note that in both equations, T does not depend on what the solute is, but only on how many particles are dissolved. T b = K b m T f = K f m

50 Colligative Properties of Electrolytes Since these properties depend on the number of particles dissolved, solutions of electrolytes (which dissociate in solution) should show greater changes than those of nonelectrolytes.

51 Colligative Properties of Electrolytes However, a 1 M solution of NaCl does not show twice the change in freezing point that a 1 M solution of methanol does.

52 van t Hoff Factor One mole of NaCl in water does not really give rise to two moles of ions.

53 van t Hoff Factor Some Na + and Cl reassociate for a short time, so the true concentration of particles is somewhat less than two times the concentration of NaCl.

54 The van t Hoff Factor Reassociation is more likely at higher concentration. Therefore, the number of particles present is concentration dependent.

55 The van t Hoff Factor We modify the previous equations by multiplying by the van t Hoff factor, i T f = K f m i

56 Osmosis Some substances form semipermeable membranes, allowing some smaller particles to pass through, but blocking other larger particles. In biological systems, most semipermeable membranes allow water to pass through, but solutes are not free to do so.

58 Osmosis In osmosis, there is net movement of solvent from the area of higher solvent concentration (lower solute concentration) to the are of lower solvent concentration (higher solute concentration).

59 Osmotic Pressure The pressure required to stop osmosis, known as osmotic pressure, π, is π = ( n V )RT = MRT where M is the molarity of the solution If the osmotic pressure is the same on both sides of a membrane (i.e., the concentrations are the same), the solutions are isotonic.

60 Osmosis in Blood Cells If the solute concentration outside the cell is greater than that inside the cell, the solution is hypertonic. 고장성용액 Water will flow out of the cell, and crenation( 축혈 ) results.

61 Osmosis in Cells If the solute concentration outside the cell is less than that inside the cell, the solution is hypotonic. 저장성용액 Water will flow into the cell, and hemolysis( 용혈 ) results.

62 Molar Mass from Colligative Properties We can use the effects of a colligative property such as osmotic pressure to determine the molar mass of a compound.

63 Colloids: Suspensions of particles larger than individual ions or molecules, but too small to be settled out by gravity.

65 Tyndall Effect Colloidal suspensions can scatter rays of light. This phenomenon is known as the Tyndall effect.

66 Colloids in Biological Systems Some molecules have a polar, hydrophilic (water-loving) end and a nonpolar, hydrophobic (waterhating) end.

67 Colloids in Biological Systems Sodium stearate is one example of such a molecule.

68 Colloids in Biological Systems These molecules can aid in the emulsification of fats and oils in aqueous solutions.

aids its cleaning action Soaps are biodegradable Soaps produce insoluble salts with divalent metal ions, predominantly calcium, which

70 Soaps, Detergents, and Detergent Builders Soaps are salts of long-chain fatty acids Sodium stearate: C 17 H 35 CO 2 - Na + 70 Soaps form spherical micelles which may entrain water-insoluble grease and oil particles (right) Soap lowers water surface tension which aids its cleaning action Soaps are biodegradable Soaps produce insoluble salts with divalent metal ions, predominantly calcium, which removes them from water, but reduces their effectiveness as cleaning agents in hard water Calcium stearate: Ca 2+ (C 17 H 35 CO - 2 ) 2 (s)

슬라이드 제목 없음

슬라이드 제목 없음 물리화학 1 문제풀이 130403 김대형교수님 Chapter 1 Exercise (#1) A sample of 255 mg of neon occupies 3.00 dm 3 at 122K. Use the perfect gas law to calculate the pressure of the gas. Solution 1) The perfect gas law p