Môn Hóa Lý: Chapter 10 liquid vapour

PHYSICAL CHEMISTRY Chapter 10 – Solution and Liquid-vapor equilibrium Dr Ngo Thanh An Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Solutions: solute and solvent Solutions • are homogeneous mixtures of two or more substances • consist of a solvent and one or more solutes Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Nature of solute in solution Solutes • • • • spread evenly throughout the solution cannot be separated by filtration can be separated by evaporation are not visible but can give a color to the solution Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Examples of solutions • The solute and solvent in a solution can be a solid, liquid, and/or a gas Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Water • • • is the most common solvent is a polar molecule forms hydrogen bonds between the hydrogen atom in one molecule and the oxygen atom in a different water molecule Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Combination of solutes and solvents in solutions Possible combinations of solutes and solvents Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Formation of a solution Na+ and Cl– ions • on the surface of a NaCl crystal are attracted to polar water molecules • are hydrated in solution by many H 2O molecules surrounding each ion Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Like dissolves like Two substances form a solution • • when there is an attraction between the particles of the solute and solvent • when a nonpolar solvent such as hexane (C6H14) dissolves nonpolar solutes such as oil or grease when a polar solvent (such as water) dissolves polar solutes (such as sugar) and/or ionic solutes (such as NaCl) Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Water and a polar solute Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Like dissolves like Solvents Solutes Water (polar) CH2Cl2 (nonpolar) Ni(NO3)2 (polar) I2 (nonpolar) 10 Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation More vapor forms; rate of condensation of that vapor increases … Liquid–Vapor Equilibrium … until equilibrium is attained Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation • • • • • Boiling point: the temperature at which the vapor pressure of the liquid equals the external pressure Normal boiling point: boiling point at atm Critical temperature (Tc): the highest temperature at which a liquid can exist The critical pressure, Pc, is the vapor pressure at the critical temperature The condition corresponding to a temperature of Tc and a pressure of Pc is called the critical point Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation (i) Simple distillation- difference in boiling points of compounds is more than 40ºC e.g.– chloroform (b p 334K) and aniline (b p 457K) Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation (ii) Fractional distillation- difference in boiling points of compounds is less than 40ºC e.g – acetone (b p 329K) and methyl alcohol (b p 338K) Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation (iii) Vacuum distillation- used for organic compounds which decompose at or below their boiling points e.g Glycerol Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation (iv) Steam distillation- used for organic compounds which are immiscible with water and are steam volatile e.g Aniline Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium III Distillation How to remove the aezotrope point? T P1 Changing pressure Adding the third component P2 P3 A xB→ B Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium IV Two-immiscible component solution The total vapor pressure above an immiscible system is equal to the sum of the vapor pressures independent of their relative amounts PT = P˚A + P˚B + P˚C + … The mixture will boil at a temperature typically lower than either liquid The mole fraction of each component (nA and nB) in the vapor phase is given by the ratio of its partial pressure over the total pressure: nA = P˚A/PT and nB = P˚B/PT If the vapor is condensed, the resulting distillate has the same composition The ratio of the mole fractions for A and B in the distillate is then given by equation: nA/nB = P˚A/P˚B Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium IV Two-immiscible component solution Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium IV Two-immiscible component solution A o T A • Pout PB Pout = PA + PB # • PA Pout • o T mixture B o T B Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium IV Two-immiscible component solution Application: Steam distillation gH O PH0 O M H O PH0 O 18 = = PA M A PA M A 2 Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium IV Two-immiscible component solution 65 Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium V Partially miscible liquid Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Lever rule V Partially miscible liquid TC n3   T3 n2 T2 T1 n1 A K H b3 Q2 Q1 b2 b1 B ... and E; fat-soluble Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Gas solubility in liquid Pressure effects Chapter Chapter 10 10 –– Solution Solution... ideal equation µi =µio+ RTlnxi Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Ideal solution Chapter Chapter 10 10 –– Solution Solution and and... ionic solutes (such as NaCl) Chapter Chapter 10 10 –– Solution Solution and and Liq Liq –– Vap Vap equilibrium equilibrium Water and a polar solute Chapter Chapter 10 10 –– Solution Solution and