Chemistry - Kinetics equations

w all the equations from this unit bc they're hard as shit to memorize

average rate of disappearance

\-Δ\[A\]/Δt

How do you find an instantaneous rate of rxn?

find tangent line to a curve

How are rxn rates measured?

Observing disappearance of reactants

Order of rxn

how changing concentration of a reactant changes rate of rxn

Rate law

rate = k\[A\]^m\[B\]^n

Overall rxn order

sum of reactant orders, m+n

k

rate constant

How to derive units of k?

M/s = k (M^overall reaction order), solve for k

0th order integrated rate law

\[A'\] = -kt + \[A\]o

1st order integrated rate law

ln \[A\] = -kt + ln \[A\]o

2nd order integrated rate law

1/\[A\] = kt + 1/\[A\]o

linear fit in \[A\] v t graph

0th order rxn

linear fit in ln \[A\] v t

1st order

linear fit in 1/\[A\] v t

2nd order

0th order half life

\[A\]o/2k

1st order half life

ln \[2\]/k

2nd order half life

1/k\[A\]o

Kinetic molecular (collision) theory conditions

1. collisions must occur
2. Molecules must have sufficient energy to react
3. Molecules must have proper orientation

Activation energy

Energy for reactants to enter transition state or activation complex so chemical and molecular changes can occur

Arrhenius equation

k = Ae ^(-Ea/RT)

Solving arrhenius equation for multiple values of k

ln (k1/k2) = (Ea/R) \[(1/T2) - (1/T1)\]

Reaction Mechanisms

processes by which a reaction occurs

Elementary steps

single steps of a reaction

Molecularity

Number of molecules that participate in a step

\
1 - uni

2- bi

3 - ter

Net reaction

Sum up all rxn steps and cancel things that are on products and reactants

Intermediates

reactants/products not in net reaction

Catalysts in net rxn

Appear as both final reactants and products, may be written over arrow

Rate law of multi-step rxn

Rate law of slowest step

Catalysts

Lower activation energy