Physical chemistr Reaction Kinetics(1) Xuan Cheng Xiamen University
1 Reaction Kinetics (1) Xuan Cheng Xiamen University Physical Chemistry
Ch ical chemistr Reaction Kinetic Reaction kinetics For example G/k- mol N2(g)+H2(g8)→NH3(g) 1663 H2(g)+O2(g)→H2O() 237.19 Thermodynamics: spontaneous reactions(possible to take place) Thermodynamics: can t answer (1) how to make them happen (2)how fast they will take place (3)the reaction mechanism
2 Physical Chemistry Reaction Kinetics ( ) ( ) 2 3 ( ) 2 1 N2 g + H2 g → NH3 g For example ( ) ( ) 2 1 ( ) 2 2 2 H g + O g → H O l 1 / − G kJ mol o r -16.63 -237.19 Thermodynamics: spontaneous reactions (possible to take place) Thermodynamics: can’t answer (1) how to make them happen (2) how fast they will take place (3) the reaction mechanism Reaction Kinetics
Ch ical chemistr Reaction Kinetic Reaction kinetics Chemical Kinetics N2(g)+H2(g)→NH3(g) T.P. catalyst H2(g)+O2(g)→>H2O() T catalyst Chemical Kinetics The study of the rates and mechanisms of chemical reactions a reacting system is not in equilibrium
3 Physical Chemistry Reaction Kinetics ( ) ( ) 2 3 ( ) 2 1 N2 g + H2 g → NH3 g ( ) ( ) 2 1 ( ) 2 2 2 H g + O g → H O l T, P, catalyst T, catalyst Chemical Kinetics: Chemical Kinetics The study of the rates and mechanisms of chemical reactions A reacting system is not in equilibrium Reaction Kinetics
Ch ical chemistr Reaction Kinetic Rate of reaction Consider the homogeneous reaction(occurs entirely in one phase) aA+bB+…→>eE+fF+ (171) dn a/dt n B dnB /dt b a dt b di The rate of conversion j B anE F b dt (172) e At equilibrium, J=0
4 Physical Chemistry Rate of Reaction Consider the homogeneous reaction (occurs entirely in one phase) b a dn dt dn dt B A = / / aA+ bB +→ eE + fF + (17.1) The rate of conversion J dt dn dt f dn dt e dn dt b dn a J 1 A 1 B 1 E 1 F − = − == = (17.2) dt dn dt b dn a 1 A 1 B = At equilibrium, J = 0 Reaction Kinetics
Ch ical chemistr Reaction Kinetic Rate of reaction The rate of reaction r (173) At constant v 1 d[a 1 d B 1 de 1 dF e dt (17 mol dms. mo cms
5 Physical Chemistry Rate of Reaction = − dt dn V V a J r 1 1 A (17.3) = − = − == = = dt d F dt f d E dt e d B dt b d A a r 1 [ ] 1 [ ] 1 [ ] 1 [ ] (17.4)* At constant V The rate of reaction r mol dm-3 s -1 mol cm-3 s -1 Reaction Kinetics