Chemical Kinetics Flashcards
(17 cards)
What is chemical kinetics
Time dependance of reactions
Tell us how a reaction work
Formation of product rate equation
Rate = d[B]/dt > 0
Loss of reaction rate equation
Rate = d[A]/dt < 0
Unit of rates
M s/min ^ -1
Noation of concentration and time
[A]t, [B]t
Example
Conc at t0: [A]0,[B]0
Rate law equations
-d[A]/dt = k
-d[A]/dt = k[A]
-d[A]/dt = k[A]^2
d[B]/dt = -k[A][B]
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Equals to rate
Differential equation of the rate law
Differential on the LHS
Function [A]t,[B]t
The solution of the rate law is called the integrated rate law
it gives time dependence of reactants and products
The reaction order equations
d[A]/dt = -k[A]^n
Reaction velocity equation
v= -1/m1 x d[A]/ dt = - 1/m2 x d[B]/dt
m= coefficient
Rate law for first order reactions
d[A]/dt = -k[A] ^1= -k
- Rate proportional to concentration of reactant
- Rate not constant but varies linearly with [A]
INTEGRATED RATE LAW
ln[A] - ln[A]0 = -kt
Rate law for 0 order reactions
d[A]/dt = -k[A]^0
- Rate doesn’t depend on reactant concentration
- Rate is constant and equal to the rate equation
Absorption spectroscopy
Used to measure reaction rates
Increased absorbance per time allows to determine rate
spectroscopy + stopped flow
Used to measure reaction rates for very fast reactions
The stop flow device (Stop syringe) ensures rapid mixing of reactants
Monitoring reaction occurs via a spectroscopic readout
equation to find initial rate
d[A] / dt where t=0
how to deduce the order of a reaction
measuring initial rate at several initial reactant concentrations
Rate law
