Hóa lý 2 ĐHBK TPHCM Chương 5 Thầy Long

dung 5 2H2 + O2 2H2O G0298= - 109 kcal/mol Th c t : Ph n ng không x y Thermodynamics vs Kinetics THERMODYNAMICS ( ): cho THERMODYNAMICS không cho thông tin trình tác thành Thermodynamics vs Kinetics hóa KINETICS ( ): nghiên (REACTION RATES) (MECHANISM) Không ( Thermodynamics vs Kinetics có : ( G > 0) ( G < 0) ( ) ( G < 0) & nhanh) Thermodynamics vs Kinetics Không : : SiO2 Si + O2 G0298 (SiO2) = - 805 kJ/mol Diamond graphite G0298 (Diamond) = 2,9 kJ/mol G0298 (Graphite) = kJ/mol Thermodynamics vs Kinetics Kinetics ( ) Reaction rate ( & ) : C + O2 KINETICS CO2 Reaction mechanism ( G0298 (CO2) = - 394,4 kJ/mol ) (molecular kinetics) trình Reactants (tác Products ( Intermediates ( Các khái ) Các PU Reaction rate ( Rate laws (PT Simple reactions (PU complex reactions (PU Reaction order ( Simple reactions ) trung gian) PU) ) Complex reactions ) : 2N2O5 = 4NO2 + O2 PU Molecularity (phân PU) ) ): N2O5 = N2O3 + O2 N2O5 + N2O3 = 4NO2 Unimolecular ( phân ) Bimolecular ( phân ) Termolecular (tam phân ) Molecularity (Phân phân : H2 (k) + I2(k) = 2HI(k) ) PU) Reaction mechanism ( Elementary reactions (PU có Molecularity (Phân ) Unimolecular ( O3 tác hóa phân NO2 + NO2 rate = k [O3] phân NO3 + NO Termolecular (tam phân Br + Br + Ar (Reaction rate) Br2 + Ar* Reaction rate : mol tích mol tác tích W gian gian +: - : ) O2 + O Bimolecular ( dN i V dt Ni Ni tác ) ) rate = k [NO2]2 ) rate = k [Br]2[Ar] nv mol.lit-1.s-1 M.s-1 Reaction rate Reaction rate ( ): = k1 Step 1: NO(g) + Br2(g) NOBr2(g) k-1 Step 2: NOBr2(g) + NO(g) k2 dN i V dt W Trong pha khí (gas phase) (fast) V= constant 2NOBr(g) (slow) = dCi dt W Trong pha (liquid phase) Reaction rate Law of mass action aA + bB = dD + eE T W dC A dt a dCB b dt a dCD d dt / tích a dCE e dt (M.Guldberg P Waage) trình A+B products W = k.[A].[B] Là ph ng trình bi u di n m i quan h gi a t c ph n ng n ng tác ch t/s n ph m For elementary/simple reactions only trình simple reactions complex reactions (Rate laws) W = f (C) (Rate laws) Law of mass action ? trình aA + bB Rate laws (Rate laws) quát : dD + eE W = k[A]m [B]n k= m, n = (rate constant) (order of reaction) aA + bB dD + eE W = k.[A]m [B]n m: n: (m+n): theo A theo B / Tuân theo ? (1st Order Reaction ) (zero order Reaction) PT =0 : W= k.CA0 = k Expt CA (M) PT Rate (M/s) =1 : W= k.CA1 Expt CA (M) Rate (M/s) 0.50 1.00 0.50 1.00 1.00 1.00 1.00 2.00 2.00 1.00 2.00 4.00 (2nd Order Reaction) PT =2 : W= k.CA2 Expt CA (M) (3rd Order Reaction) : W= k.CACB PT Rate (M/s) =3 : W= kCA3 ; W= kCA2CB Expt CA (M) Rate (M/s) 0.50 0.50 0.50 0.25 1.00 2.00 1.00 2.00 1.50 4.50 1.50 6.75 Quan / gian Quan / gian Half-life time (t1/2): t = t1/2 : CA =CA0/2 (Th i gian/chu bán h y) Average life time ( ): t = : CA =CA0/e (Th i gian/chu s ng trung bình) dC A dt W V k0 CA vs t : CA CA0 k0t ng th ng H s góc : k0 (mol.lit-1.s-1) Quan / CA gian CA0 tg = -k0 CA CA0 k0t t1/ C A0 2k t (const) = CA0(e-1)/ek1 Quan / gian lnCA W dC A dt V lnCA0 ln CA ln CA0 k1t C ln A k1t C A0 k1C A lnCA vs t : tg = -k1 ng th ng t H s góc : k1 (s-1) Quan / gian Quan / ln gian CA C A0 TH 1: k1t 2A const ln k1 t1/ products A+B products CA0 = CB0 A+B products CA0 TH 2: 0,693 k1 CB0 = 1/k1 Quan / gian Quan / TH 1: 2A products A+B W gian dC A dt products CA0 = CB0 TH 1: dC A dt W V k2C 2A k2C 2A 1/CA vs t : CA C A0 ng th ng H s góc : + k2 (mol-1.lit.s-1) k2t Quan / 1/CA TH 1: tg CA = k2 1/CA0 C A0 t Quan / gian Quan / gian TH 2: TH 2: A+B products with CA0 dC A dt W kC A CB Quan CB0 W t= : CA= CA0; CB= CB0; t= t : CA= CA; CB= CB; dC A dt kC A CB CB= CA + CA0 - CA= CB0 CB CB0 CA0= CB CA = = const / gian Quan / CB= CA + kt (const) k C A0 t1/ TH 2: gian gian dC A dt W CB C A kC A CB ln C A0 CB CB C A TH 2: CB C A ln C A0 CB CB C A Ü¿1²¹ ¬«§»?² ¬3²¸æ k 2t ln CB CA (CB0 C A0 )k2t ln Quan / ln(CB/CA) tg = (CB0-CA0)k2 TH 2: ln(CB0/CA0) t k2 t CB C A ln C A0 CB CB C A k 2t CB C A0 gian Quan / 3( 3A gian ) products W dC A dt C 2A k3C 3A C 2A 2k3t Quy Reversible reactions (PU ) tuân theo Parallel reactions (PU song song) Consecutive reactions (PU trong ) aA + bB aA + bB dD + eE k k' k k' dD + eE k aA + bB k' Lúc cân (equilibrium): dD + eE aA + bB W k.C aA C bB d k.C aA eq C bB eq dD + eE W k '.C Dd eq C eE eq k k' e W ' k '.C D C E C Dd eq C eE eq C aA eq C bB eq (Quan 1-1 reversible reactions: A t= : CA= CA0; CB= CB0; t= t : CA= CA; CB= CB; t: X = CA0 CA CB0 CB = -X B CA = CA0 X CB = CB0 + X Equilibrium: CA-eq = CA0 X CB-eq = CB0 + X cân W' 1) 1-1 reversible reactions: A CA = CA0 X CB = CB0 +X W dC A dt dX dt k1 (C A ln X X X k1 C A B k1 '.C B X ) k1 '.(C B (k1 k1 ' )t K X) 1-1 reversible reactions: A (1) K (2) ln k1 k1 ' CB eq CA eq X X CB C A0 B ln[(X -X)/ X ] t X X tg = -(k1 + k1 (k1 k1 ' )t X song song 1-2 reversible reactions: A B+D A 2-2 reversible reactions: 2A B+D W song song A dC A dt W k1 B k'1 C (k1 dC A dt tg = -(k1 1) ln C A B k'1 C (k1 WB dCB dt k1 C A WC dCC dt k1' C A k1 ' ).C A song song k1 ' ).C A A lnCA lnCA0 k1 k1 B k'1 C ln C A0 (k1 k1' )t t= 0: CB0= CC0 = Quan t= t : CA0 = CA + CB + CC t song song A k1 B k'1 C WB= dCB/dt = k1.CA WC= dCC/dt 1.CA song song ln(CA0/CA)= (k1 1)t CA CB WB= dCB/dt = k1.CA dCB/dCC = k1/ CB/CC = k1/ WC= dCC/dt CC 1.CA CB (CB0 = CC0 = 0) CC A C A0 e k1 k1 B k'1 C ( k k1') t C A0 (1 e k1 k1 ' k1 ' C A0 (1 e k1 k1 ' k1 ( k k 1') t ) ( k k 1') t ) (C A0 C A ) k1 k1 ' k1 ' (C A0 C A ) k1 k1 ' song song A CB/CC = k1/ Quan k1 CB k1 k1 ' k1 B k'1 C C A0 (1 e ( k k 1') t ) ( k k 1') t ) song song k1 A A+B k2 B k'1 C k1 ' C A0 (1 e k1 k1 ' CC k1 A song song k1 C A D A+B CA -dCA/dt = k1.CA + k2.CA.CB -dCB/dt = k2.CA.CB C0 A C0 B dC B dt k2 CB C D k1 CB ln k C0 B k 2CB (C0 A C0 B CB k1 C B ln ) k C0 B A k1 A B k'1 C -dCA/dt = k1.CA dCB/dt = k1.CA dCC/dt 1.CB (B: intermediate) t= 0: CB0= CC0 = t= t : CA0 = CA + CB + CC CB CC CA CB CC C A0 e k1t k1 C A0 (e k k1 k1t e k 2t ) k1 B k2 C k2= 0.5k1 CB C A0 C A CB C A0 e CC C A0 e k1t k1 C A0 (e k k1 k1t e k 2t ) k1 C A0 (e k1 ' k1 k1t e k1 B k2 t= tm : dCB/dt =0 C A0 C A CB tm k2= 10k1 C k1 't ) C A0 C A CB k1 k2 k1 k2 ln k2= 2k1 k'1 k1t A CA B 1.CB CA A k1 C A C B , max k1 >> B: k1 CA0) CB= const zero order W = k CBm pháp (CA0 >> CB0) CA= const zero order 1st order 1st order 2nd n= theo A Xác 2nd order order nth order m= theo B BPU CA W = k CAn pháp vi phân CA1 tangent line W= - dCA/dt W = k CAn ln W tg =n t lnk lnW = lnk + n.lnCA lnCA W= - dCA/dt - CA/ t Van Xác BPU Xác pháp vi phân + CB0= const, Thay lnW2=lnk + n.lnCA0,2 + m.lnCB0 CA0= const, Thay W4 = k CA0n CB0,2m lnW4=lnk + n.lnCA0 + m.lnCB0,2 , ) 1: W = k CAn lnCA0 tg lnW3=lnk + n.lnCA0 + m.lnCB0,1 PU n CB0: W3 = k CA0n CB0,1m ý: Trong pháp tích phân (PP lnCA lnW1=lnk + n.lnCA0,1 + m.lnCB0 + BPU CA0: W2 = k CA0,2n CB0m CA0,1n CB0 W = k CAn CBm m W1 = k nth order thay m ln CA = -k1 ln CA0 k1t tra t Xác BPU Xác W = k CAn pháp tích phân BPU pháp tích phân 1/CA CA Gi s PU b c 2: Gi s PU b c 0: tg CA C A0 k2t W = k CAn CA0 = k2 tg CA 1/CA0 = -k0 CA0 k0t tra tra t Xác PP t BPU Xác gian phân 1/q PP BPU gian phân (1/q-conversion time method) q=2 PP gian bán W = -dCA/dt= k CAn C An 1 C An 01 (n 1).k t t=t1/q : CA= CA0/q qn C An 01 C An 01 (n 1).k t1 / q C An 01 (n 1).k t1/ q (q n 1) (half-life time method) ln t1/ q Xác PP W = k CAn 1/q (1 n) ln C A0 ln (n 1).k (q n 1) BPU gian phân 1/q ln t1/ q (1 n) ln C A ln (n 1).k (q n 1) ln t1 / (1 n) ln C A ln (n 1).k (2n 1) W = k CAn (n 1) Rate Rate Quy Khi hoá Rate Van k (T T T T 10.n ) lên 10 lên 2-4 n kT Vant Hoff Jacobus 1852-1911 Svante Arrhenius Nobel prize 1903 trình Arrhenius: vi phân: k: Ea : trình Arrhenius: hoá tích phân: lnk T1= 295 K T2= 305 K R= 8,314 J/mol.K lnk0 tg = -Ea/R k (T Kho ng nhi t yêu c u t i thi u xác nh Ea: (20-25)o 1/T k (T 10 n ) kT n ? 10.n ) kT n ? ... : 2N2O5 = 4NO2 + O2 PU Molecularity (phân PU) ) ): N2O5 = N2O3 + O2 N2O5 + N2O3 = 4NO2 Unimolecular ( phân ) Bimolecular ( phân ) Termolecular (tam phân ) Molecularity (Phân phân : H2 (k) + I2(k)... W= kCA2CB Expt CA (M) Rate (M/s) 0 .50 0 .50 0 .50 0 . 25 1.00 2. 00 1.00 2. 00 1 .50 4 .50 1 .50 6. 75 Quan / gian Quan / gian Half-life time (t1 /2) : t = t1 /2 : CA =CA0 /2 (Th i gian/chu bán h y) Average... ' k1 1: 2: CB,max C0A trung gian k 1' k1 k1 CM k1 CA k4 2k1.C A 2k4 C k3 CM 2C A 2k4 CM2 k2 CM 1CB k3 CM 2C A M1 0 dC A k1 C A k3 CM 2C A k4 CM2 dt dCB k CM 1CB dt dCC k2 CM 1CB k3 CM 2C A dt