Unit 9: Kinetics
●Need experimental data to find out how fast the reaction is, the balanced reaction does
not provide that info
●Half-Lives: the time it takes for ½ of the existing sample to disappear
○1st order reactants
●Collision Theory
○Particles Must Collide
○Particles need to have enough energy to break old bonds when they collide
■The minimum required is called the activation energy
●Tied to the strength of reactant bonds (the ones being broken)
●As temperature increases, activation energy increases
○Particles need to be in the correct orientation (angle) to create product
○Very unlikely that the reaction occurs in one step
■ex. 6 particles colliding at once at the perfect angle
●The rate for each substance (increasing or decreasing) relates to the coefficients (ratios)
●Rate (overall reaction) = k[A]x[B]y
○K = rate constant
○As temperature increases, the k increases
○k’s units CHANGE
■“The canceller”
●Order:
○In respect to A: xth
○In Respect to B: yth
○Overall order: (x+y)th
○To determine the order of a reactant:
■Using a table:
●Keep the other reactant(s) constant
●Determine how the rate is affected by the reactant
■Using graphs:
●Concentration v time: straight
○0th order
●ln[concentration] vs time: straight
○1st order
●1/[concentration] vs time: straight
○2nd order
●Algebraically: use equations on the formula sheet
●To make the other reactant(s) not have an effect:
○Make them have very high concentrations
