Môn Hóa Lý: Chapter 11 solid

PHYSICAL CHEMISTRY Chapter 11 – Phase equilibrium involving solids Dr Ngo Thanh An Chapter 11 – Equilibrium involving solids Content Freezing Point – Boiling Point – Osmotic pressure Two- component solid – liquid phase diagrams Three- component solid – liquid phase diagrams Chapter 11 – Equilibrium involving solids Freezing Point – Boiling Point – Osmotic pressure Vapor pressure depression No No solute solute vapor vapor  total total vapor vapor pressure pressure of of the the solution solution is is the the vapor vapor pressure pressure of of the the solvent solvent vap vap vap vap Raoult’s Raoult’s law: law: P P == P Psolv = = P P x x = = P P (1-x) solv solv solv solv solv solv solv (1-x) Where: Where: P P :: solution solution vapor vapor pressure pressure vap P Pvap vapor pressure pressure of of the the pure pure solvent solvent solv solv :: vapor xx :: total total mole mole fraction fraction of of solutes solutes Vapor pressure depression vap solv P  P vap solv P  P vap solv P x Higher the concentration of the solutes, the lower the vapor pressure Freezing Point & Boiling Point • Freezing Point depression and Boiling Point elevation: T = K.Cm Where: Cm : molarity (mol solute / 1000g solvent) RT02 M K 1000 (Applicable to very dilute solution) Freezing Point & Boiling Point Parameter T (K)  (cal/mol) To (K) Boiling point Elevation Freezing point Depression Heat of vaporization Heat of fusion Solvent’s boiling point Solvent’s freezing point R = 1,987 (cal/mol/K) : gas constant M2 (g/mol) : Solvent molar weight Freezing Point & Boiling Point Examples: – 50% NaOH: boiling point  1200C – 22% NaCl in water: freezing point -21 0C Osmotic pressure Osmotic pressure (): (): is is the the minimum minimum pressure pressure which which needs needs to to be be applied applied to to aa solution solution to to prevent prevent the the inward inward flow flow of of water water across across aa semipermeable semipermeable membrane membrane 10 In-Class activity Compute the osmotic pressure of the solution: Sucrose in water at 293 K at: C= 0.1 mol/l; comparing to  (measured)= 262 kPa C= 0.75 mol/l; comparing to  (measured)= 2,4 MPa 12 Two-component Solid – liquid phase diagrams 13 Two-component systems • Simplest solid-liquid phase diagram (two components) ToC b Liquid (A + B) a When crystallizing: SA  L SA e A -no solid solution SB  L SA + SB xB  SB -react to form a unstable compound B Example: NaCl – H2O; KCl – LiCl; MgO – CaO; naphthalene - diphenyamin… 14 Two-component systems • Crystallization To C Q l1 a l2 SA + SB A b s1 T1 Q2 s2 T2 SB  L SA  L SA P= const e H SB T e E xB  B System point Liquid phase’s point Solid phase’s point T Q Q - - l1 l1 s1 T1 Q2 l2 s2 T2 H e SB Te Degrees of freedom 15 Two-component systems To C Q l1 a l2 SA + SB A Q2 s2 T2 Q22= liquid(l22) + solid(s22) SB  L SA  L SA b s1 T1 Amount of phase, example at Q2: e H SB T e E xB  B g (s2 ) l2Q2  g (l2 ) Q2 s2 Lever rule! 16 Two-component systems At H: TC - phases: Solid A (sA) , Solid B (sB), Liquid AB (e) - Liquid “e” crystallize  Solid A and solid B o b Q a Continue the cystalization: sA S + S A B rC : move from rB to H SB  L SA  L A - Solid system (SC): = Solid A + Solid B e E H xB  Te sC sB g ( RC ) eH  g ( Le ) HRC B Kết tinh kết thúc khi: rC = H 17 Two-component systems • Eutectic mixtures ToC Liq A + B b at at P= P= const: const: Q Eutectic Eutectic mixtures mixtures melt/crystallize melt/crystallize at at constant constant temperatures temperatures a SB  L SA  L sA S + S A B A Te sB e E xB  Composition Composition of of Solid= Solid= Composition Composition of of liquid liquid Solid Solid phase: phase: mixture mixture of of fine fine crystal crystal of of solid solid A A ++ solid solid B B B 18 Two-component systems • Eutectic mixtures If P const: - Number of degrees of freedom: F = C – P +2 = When P change:  Tee change and xee change 19 Two-component systems • Applications of Eutectic mixtures: Cooling Cooling agent agent (NaCl(NaClH H22O): O): :: NaCl NaCl –– H H22O O (23,3%wt (23,3%wt NaCl): NaCl): TTee == -21,2 -21,2 00C C Eutectic Eutectic alloys alloys for for soldering, soldering, composed composed of of tin tin (Sn), (Sn), lead lead (Pb) (Pb) :: TTee