1. Describing Reactions Stoichiometry Thermodynamics Kinetics concerned with the speed or rates of chemical reactions reacting ratios, limiting and excess reagents reaction spontaneity

2. Reaction Rates Br 2 + HCOOH  2Br - + 2H + + CO 2 change in concentration change in time Rate =   [Br 2 ] tt

4. Time (s)[Br 2 ] (M) 0.00.0120 50.00.0101 100.00.00846 150.00.00710 200.00.00596 250.00.00500 300.00.00420 350.00.00353 400.00.00296 Br 2 + HCOOH  2Br - + 2H + + CO 2 3.80 x 10 -5 M/s 1.14 x 10 -5 M/s Instantaneous Rate

5. Br 2 + HCOOH  2Br - + 2H + + CO 2 Rate =   [Br 2 ] tt = 2.96 x 10 -5 M/s

6. Reaction Rate and Stoichiometry Br 2 + HCOOH  2Br - + 2H + + CO 2 Rate of change of Br - ? Rate =   [Br 2 ] tt = 2.96 x 10 -5 M/s Rate =   [Br 2 ] tt =  [Br - ] tt 1 2 = [H+ ][H+ ] tt 1 2 =   [HCOOH] tt

7. Reaction Rate and Stoichiometry aA + bB  cC + dD Rate =  [A ][A ] tt 1 a =  [B ][B ] tt 1 b = [C][C] tt 1 c = [D][D] tt 1 d

8. Rate Laws expresses relation of rate of reaction to concentrations of reactants A + B  C  rate = k [A] x [B] y  rate constant. temperature dependent “order” of the reaction with respect to each reactant NOT based on coefficients!!! determined experimentally

9. A + B  C [A] (M)[B] (M)Rate (M/s) 0.10 0.20 0.100.40 0.300.100.60 0.300.202.40 0.30 5.40 rate = k [A] x [B] y

10. Reaction “Order” rate = k [A] rate = k [A] 0 first order zero order

12. Reaction Mechanism (CH 3 ) 3 CBr + OH -  (CH 3 ) 3 COH + Br - rate = k [(CH 3 ) 3 CBr] 1 [OH - ] 0

13. slow step fast step

15. slow step fast step rate = k [(CH 3 ) 3 CBr] 1 [OH - ] 0

16. Reaction “Order” rate = k [A] rate = k [A] 0 rate = k [A] 2 [B] 1 first order zero order second order with respect to A first order with respect to B third order overall

17. Unit of Rate Constant ( k ) depends on overall order of the reaction To determine the value and units of k, use data from one trial and sub into rate law. rate = k [A] 1 [B] 2 0.20 = k [0.10] 1 [0.10] 2 k =200