Physical 3 Flashcards
First order rate equation
A=A0 * e^-kt
Or
Ln(A0/A) = kt
First order rate in terms of Products and derivation?
A0 = final Pconc
Thus, P=Pconc (1-e^-kt)
Ln(1-P/Pconc)= -kt
Second order reactions with respect to one reagent? Aka- A+A
-dA/dt = kA^2
1/A - 1/A0 =kt
Plotting 1/A= …
First order with respect to two reagents of unequal conc?
Second order
A= A0-x. B=B0-x
1/(A0-B0) (ln(B0/A0 * A/B) )=kt
Multiply by denominator then separate logs-
Ln(A/B)= (A0-B0)kt -ln(B0/A0)
Steady state approximation assumption-
It is assumed that after an initial induction period, the concentration of all reaction intermediates will rise from zero and then in the main part of the reaction, the rate of change of concentration of all intermediates is negligibly small. If intermediate I is highly reactive, dI/dt~0
K1 k2
A—B—C
Which factors must be true for steady state approx?
K2»K1 and t» 1/k2
How to tell if something is intermediate?
The compound will never appear in the overall chemical/stoichiometric equation. The concentration will always be 0.
Coulomb’s formula: what is it about?
The electrostatic interaction between two charged particles separated by a distance r in a vacuum. V is coulombic potential energy of interaction…
V= Q1 * Q2/ 4pi * Ē0*r
E is epsilon nought and stands for vacuum permittivity.
Dielectric constant (Er) also known as relative permittivity of medium (solvent/air etc)
Er =E/E0
How to find factor of difference in rate between solvents?
Divide rate of appropriate solvent by rate of worse solvent to get a factor
What does the double dagger mean?
Excited state (transition state)
In transition state theory, what is rate of reaction given as?
The rate of reaction is given by the rate of crossing the transition state.
Rate coefficient for TST?
(Eywing equation)
k= (Kb *T/ h) * k double dagger
TST rate coefficient in terms of Gibbs?
(Modified version of Eywing equation)
k= (Kb * T/h) * e^-deltaG/RT
Where Kb is Boltzmann and delta is a triangle.
A rate increase is favoured by an increase in free energies of reactants, true or false? Explain.
True. The reactants having greater free energy means it they are destabilised and therefore are more likely to react/possess higher energies.
True or false? A rate increase will favour an increase in the free energy of the transition state?
False. The free energies of the transition state will decrease with a rate increase. The transition state will become more stable and therefore lower in energy, making it easier to achieve so the reaction can progress quicker.
