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 As a reaction proceeds, there is a decrease in concentration of reactants and an increase in the concentration of the products  N 2 + 3H 2  2NH 3  N 2 and H 2 decrease in concentration over time, while NH 3 increases in concentration over time.

 Average reaction rate  Concentration M 2 - Concentration M 1 t 2 - t 1   [Concentration]  time  Reaction rates must always be positive  If you get a negative reaction rate, change the sign to positive

1. Reacting substances (atoms, ions, or molecules) must collide. 2. Reacting substances must collide with the correct orientation 3. Reacting substances must collide with sufficient energy to form the activated complex.

 The minimum amount of energy that reacting particles must have to form the activated complex and lead to a reaction  Symbol: E a  Direct influence on the rate of a reaction

Exothermic inc time inc energy

Endothermic F inc time inc energy

Given H 2 + Cl 2 2HCl 1.Calculate the average reaction rate expressed in moles H 2 consumed per liter per second 2.Calculate the average reaction rate expressed in moles Cl 2 consumed per liter per second – – 0.00 = M/s – – 0.00 = M/s  [Concentration]  time

 An expression that relates rate of a reaction and reactant concentration  Rate of reaction depends on reactant concentrations  never includes products  Given: 2A + 3B 2C ◦ In general, rate = k [A] x [B] y

 Symbol: k (lowercase)  A constant specific and unique for every reaction  If k is large, products form quickly  If k is small, products form slowly

 Exponents in rate law (x and y)  Determine how much the rate depends on the respective concentration(s)  Can ONLY be determined by experiment  Overall order of a reaction is the sum of all orders (x + y)

 2A + 3B 2C  Skeleton Rate = k [A] x [B] y  Overall order of reaction (x + y) If x=1, 1 st order in A If y=2, 2 nd order in B Overall order = 3 rd order

Write the skeleton rate law 2H 2 O ( l ) 2H 2 (g) + O 2 (g) rate = k [H 2 O] x

 Example 1: rate = k [A] 1 st order ◦ If concentration of A doubles, rate doubles ◦ If concentration of A triples, rate triples ◦ If concentration of A is halved, rate halves  Example 2: rate = k [A] 2 2 nd order ◦ If concentration of A doubles, rate quadruples ◦ If concentration of A triples, rate is 9 times as fast **directly proportional **exponentially proportional

 Example 3: rate = k [A] 0 0 th order ◦ Recall: anything raised to the 0 th power = 1 ◦ If the concentration of A changes in any way NOTHING happens to the rate ◦ Rate is not dependent on concentration ◦ Rate = k

 Given: rate = k [A] 2 [B]  What is the overall rate if A doubles and B is halved? ◦ A is 2 nd order so if A doubles, rate is 4x ◦ B is 1 st order so if B is halved, rate is halved **overall change in rate is the multiplication of each rate change ◦ 4 × ½ = 2 ◦ The rate is 2x as fast overall