Kinetics Thermodynamics spontaneity of reaction G 0 spontaneous

Kinetics Thermodynamics : spontaneity of reaction G < 0 spontaneous 2 H 2(g) +O 2(g) 2 H 2 O(l) Go = -474 k. J Go = Ho - T So a) low T o H < 0 favorable b) high T o S < 0 unfavorable Thermodynamically spontaneous very slow

Kinetics: Kinetics rates of reaction mechanism of reaction O 2( 2 H 2 O(l) Greaction < 0 2 H 2(g) + g) Greactants Gproducts thermodynamics kinetics thermodynamics

Kinetics 2 H 2(g) + O 2(g) 2 H 2 O(l) - - - + - - - P. E. n-e + - qn qe r Go = -474 k. J spontaneous - - - + - - -

Low Temperature

High Temperature

High Temperature P. E. endothermic exothermic 0 r (distance) - -- +- -- -

Kinetics rate of reaction [reactant] [product] decrease increase 1. Temperature (K. E. ) 2. Concentration 3. Orientation

differential rate laws A+B C rate = a) +- [A] = - [B] = + [C] t t b) - t A+B 2 C rate = - [A] = - [B] = 1 [C] 2 t t t A+B C +

100 x [ ] x x 50 x x x 0 1 2 3 4 time (min) ave. rate = [ 5 t (min) 0 100 1 72 2 52 3 37 4 27 5 19 100 72 52 37 27 19 ] = 81 - 0 = 16. 2 min-1 t 5 -0 ave. rate = - [ ] = - (19 - 100 ) = 16. 2 min-1 5 -0 t 0 28 48 63 73 81

100 x [ ] x x 50 x x x 0 1 2 3 4 time (min) 5 t (min) 0 100 1 72 2 52 3 37 4 27 5 19 100 72 52 37 27 19 ave. rate = - (19 - 100) = 16. 2 min-1 overall 5 -0 ave. rate = - (72 - 100) = 28. 0 min-1 1 st minute 1 -0 ave. rate = - (19 - 27) = 8. 0 min-1 5 th minute 5 -4 0 28 48 63 73 81

100 x [ ] x x 50 x x x 0 1 2 3 4 time (min) 5 slope of line tangent to curve = instantaneous rate at t = 0 initial rate fastest rate

t (min) 0 1 2 3 4 5 instantaneous k = rate [reactant] rate 100 72 52 37 27 19 33. 0 23. 8 17. 2 12. 2 8. 9 6. 3 rate [reactant] = k [reactant] k = rate constant 0. 33

k= rate [reactant] k independent of [reactants] k dependent on Temperature a [B]b [C]c. . . [A] rate = (- [A]) = k t k, a, b and c determined experimentally isolation method