CHEM 112 - MIDTERM II Flashcards
Reaction with a faster rate will have more _____.
products formed
Rate expression
rate = -1/a [A]/ t = -1/b [B]/ t =- 1/c [C]/ t
Average rate vs. instantaneous rates
Average rate: rate of the reaction over a certain period of time (takes the two time points from initial to final to find the change in concentration)
Instantaneous rate: rate of the reaction at a given time (ie. t = 2 s)
The rate of the reaction is ____ to the concentration of the reactants
proportional
The rate constant depends on ____ & ____.
Temperature & reaction specific properties
rate law
rate = k [A]^ x [B]^y
where x & y are integers that give the order of the reaction w/ respect to each reactant
Zero order
No dependence on the concentration ([A]0 = 1); change in concentration does not equal change in rate
First order
The rate of the reaction is directly proportional to the reactant concentration ([A]^1 = [A])
Second order
The rate of the reaction is directly proportional to the square of the reactant concentration ([A]^2 = [A]^2)
Integrated rate law
Describes the relationship between the concentrations of the reactants and time (depends on the order of the reaction)
Zero order Integrated Rate Law
[At] = -kt + [A]0
First order IR Law
ln [A]t/[A]0 = -kt
Second order IR Law
1/[A]t = kt + 1/[A]0
Slope for zero order IR
-k
Slope for first order IR
-k
Slope for second order IR
+k
Half-life
Time required for the concentration of a reactant to fall to 1/2 of its initial value
Find half-life on graph
see y-intercept and divide by 1/2 - the x-intercept (time) = half life
Zero order half life
t 1/2 = 1/k x [A]0/2
First order half life
t 1/2 = 1/k * 0.693
Second order half life
t 1/2 = 1/k x 1/[A]0
Factors that affect reaction rates
1) Concentrations
2) Temperature
3) Catalysts
Catalysts ____ the activation energy by providing a ____ energy path from reactants to products
lower; alternate, lower energy path
Arrhenius Equation
Relates the rate constant (k) and the temperature in kelvins
k = A x e^ -Ea/RT