C14 - Chemical Kinetics (Gen. Chem 2)

rate law

equation relation concentrations to reaction speed (in molarity/s))

reaction rate

(d[A]/dt)(1/a)

• [A] = concentration of A

• a = # mols

k

rate constant (varies by temperature)

1st order

∆M is directly proportional to reaction speed

• ln[M]_t = -kt + ln[M]₀

• t_1/2 = 0.693/k

2nd order

∆M is proportional to reaction speed by the square

• 1/[A]_t = kt + 1/[A]₀

• t_1/2 = 1/2[A]₀

0 order

∆M does not affect rate

• [A]_t = -kt + [A]₀

• t_1/2 = [A]₀/2k

Arrhenius equation

k = Ae^-E/RT

• E = activation energy

• ln(k₁/k₂) = (E/R)(1/T₂ - 1/T₁)

• f = e^-E/RT

  • f = fraction of molecules where E ≥ E_a

activation energy graph

• ln(k) = -E/RT + ln(A)

molecularity

• unimolecular

• bimolecular

• termolecular

elementary step

1 part in an entire chemical process

• rate law for e-step = # of molecules

slow initial e-step

rate = k₁[reactant₁][reactant₂]

fast initial e-step

rate k₂(k₁/k_-1)[step 1 constituents][step 2 non-intermediate]