Chemical Kinetics

Question 1

Gibbs Free Energy (delta G)

Answer 1

change in this determines whether a reaction will be spontaneous or non-spontaneous

Question 2

Intermediate

Answer 2

the molecule that does not appear in the overall reaction

hard to detect as they are consumed immediately after they are formed

Question 3

Rate-Determining Step

Answer 3

slowest step in any mechanism

Question 4

Collision Theory of Chemical Kinetics

Answer 4

rate of a reaction is proportional to the number of COLLISIONS PER SECOND between the reacting molecules IN CORRECT ORIENTATION AND ENERGY

Question 5

Activation Energy (Ea)

Answer 5

the minimum energy required for a reaction to take place; can be called an energy barrier

Question 6

Rate of reaction Equation

Answer 6

rate = Z x f

Z = number of collisions per second

f = fraction of collisions that are effective

Question 7

Arrhenius Equation

Answer 7

k = Ae ^ (-Ea / RT)

A = frequency factor
Ea - activation energy of reaction
k = rate constant of reaction

Question 8

Frequency Factor/Attempt Frequency

Answer 8

measure of how often molecules in certain reactions collide, s^-1

can be increased by increasing the number of molecules in a reaction

Question 9

Trends of Arrhenious Equation

Answer 9

as A increases, so too does k

as T increases, value of the exponent would be less than 1, gets more positive, k increases

Question 10

Reaction Coordinate

Answer 10

traces the reaction from reactants to products

Question 11

Transition State/Activated Complex

Answer 11

greater energy than both reactions and products; activation energy required to reach this state

can revert back to products or reactants WITHOUT any energy

not an actual identity, not the same as an intermediate

Question 12

Free Energy Change of Reaction (deltaG rxn)

Answer 12

energy difference between products and reactants

Question 13

Exergonic Reaction

Answer 13

Negative free energy change between reactants and products is energy being RELEASED

Question 14

Endergonic Reaction

Answer 14

Positive free energy change between reactants and products is energy being ABSORBED

Question 15

Activation Energy Forward/Reverse Reactions

Answer 15

FR: difference in free energy between transition state and reactants

RR: difference in free energy between transition state and products

Question 16

Factors Impacting Reaction Rate

Answer 16

Reaction Concentration
Temperature
Medium
Catalysts

Question 17

Reaction Rate Factor: Concentration

Answer 17

greater the concentration, te greater the number of collisions

increases reaction rate for all BUT ZERO ORDER REACTIONS

Question 18

Reaction Rate Factor: Temperature

Answer 18

As temperature increases, so too will reaction rate

avg kinetic energy of particles increases to surpass Ea

Question 19

Reaction Rate Factor: Medium

Answer 19

some molecules re more likely to react with each other in aq vs non aq environments

polar solvents are preferred as the dipole polarizes bonds of reactants and weaken the bonds to make it easier to break

Question 20

Reaction Rate Factor: Catalyst

Answer 20

increase reaction rate without being consumed within the reaction by DECREASING ACTIVATION ENERGY (Ea)

• increase frequency of collisions
• change orientation of reactants to make collisions more effective
• donate electron density to reactants
• reduce intramolecular bonding within reactant molecules

DO NOT IMPACT Keq or the free energies of the products/reactants

DO NOT MAKE NONSPONTANEOUS REACTIONS SPONTANEOUS

Question 21

Homogeneous Catalysis

Answer 21

catalyst is in same phase as reactants (solid, liq, gas)

Question 22

Heterogenous Catalysis

Answer 22

catalysts us ub a ds=istinct phase

Question 23

Rate of General Reaction:

aA + bB -> cD + dD

Answer 23

rate (M/s) =

• delta [A] / (a(delta t))

=

• delta [B] / (b(delta t))

=

delta [C] / (c(delta t))

=

delta [D] / (d(delta t))

Question 24

For nearly all forward, irreversible reactions, the rate is _____ to the concentration of the reactant, with each concentration raised to some experimentally determined exponent.

Answer 24

proportional

Question 25

Rate Law for

aA + bB -> cD + dD

Answer 25

rate = k[A]^x [B]^y

x and y are orders of the reaction

Question 26

THE VALUES OF X and Y ARE ALMOST ____ tTHE SAME AS THE STOICHIOMETRIC COEFFICIENTS

Answer 26

NEVER

Question 27

Rate constant (k) is only a constat for a specific _____ at a specific ____

Answer 27

reaction, temperature

Question 28

For a reversible reaction, Keq =

Answer 28

Keq = k/ k^-1

(rate of forward reaction / rate of reverse)

Question 29

Experimental Determination of Rate Law

Answer 29

1) Look At Table of Experiments
2) Find 2 trials where one of the reacts is the same and the other is different
3) Divide the rates, divide the concentrations and solve for exponent
4) do the same for the other reactant
5) solve for k using newly found exponents and experimental data trial

Question 30

Zero-Order Reaction

Answer 30

rate of formation of product C is INDEPENDENT of changes in concentrations of any reactants A and B

rate = k (M/s)

*k is dependent on temperature so it is possible to change the rate of zero order via temp or catalyst just not concentration

Question 31

Plotting Zero-Order Reaction

Answer 31

slope of -k straight line

Question 32

First - Order Reaction

Answer 32

rate is directly proportional to ONLY ONE REACTANT

rate = k[A]^1 or k[B}^1

k = s^-1

ex: radioactive decay

Question 33

Radioactive Decay 1 Order

Answer 33

rate = - delta [A] / (a(delta t)) = k[A]

Question 34

First Order Reaction Concentration Substance

Answer 34

[A]t = [A]o e^ -kt

Question 35

A first order rate law with a SINGLE reactant suggests that a reaction begins when the molecule undergoes a…..

Answer 35

chemical change by itself without any chemical or physical interaction

Question 36

Plotting First-Order Reaction

Answer 36

Conc vs time will make a curve that is non linear

taking ln[A] vs time, a linear line is made where slope = -k

Question 37

Second Order Reaction

Answer 37

rate is proportional to either the concentrations of two reactions or the squared concentration of a single reactant

rate = k[A]^1[B]^1 or k[A]^2 or k[B]^2

second order suggests a physical collision between two reactant molecules, especially if the rate is: rate = k[A]^1[B]^1

Question 38

Plotting Second-Order Reaction

Answer 38

plot 1/[A] vs time and get a linear line with slope = k

Question 39

There are few high order reactions because…

Answer 39

ut us rate for three particles to collide together with the correct orientation and enough energy

Question 40

Mixed Order Reactions

Answer 40

non-integer orders (fractions) that apply to reactions with rate orders that vary over the course of a reaction

Question 41

Broken Order

Answer 41

the fraction orders for mixed order reactions