Kinetics

Question 2

what are the 4 factors that affect the rate

Answer 2

1. concentration (increases collisions)
2. physical state - SA
3. temp (increases collisions)
4. Catalysts (lowers Ea)

Question 3

if the rate value is a high number, the reaction is proceeding _____

Answer 3

fast

Question 4

if the rate value is a small number, the reaction is proceeding _____

Answer 4

slow

Question 5

is the rate always written as a positive number?

Answer 5

yes
it represents the speed
speed can not be negative
the negative tells u the behaviour of the reaction

Question 6

what does a negative rate value mean

Answer 6

solving for the rate of the reactants which is depleting as time goes on
rate = - [reactants]/time = [products]/time

Question 7

as the reaction orders increase, there is __ (more/less) of an affect on the rate

Answer 7

more

Question 8

what is the rate law affected by

Answer 8

affected by concentration (in the eqn)
temperature (from k value - only 1 k value per temperature - changes each time temp changes)

Question 9

T/F is the rate inversely proportional to the rate?

Answer 9

false
the rate is directly proportional to the rate because it forces the collisions

Question 10

does pure water or pure solids go into the rate law expression

Answer 10

no

Question 11

what does a fraction order mean

Answer 11

it means that the concentrations are increasing at a faster rate than the rate is

Question 12

what does a negative order mean

Answer 12

when the concentrations increase, the rate is negatively affected by it - and the rate decreases

Question 13

what are the units of k when the reaction order is zero

Answer 13

mol/L*s

Question 14

what are the units of k when the reaction order is one

Answer 14

1/s

Question 15

what are the units of k when the reaction order is 2

Answer 15

L/mol*s

Question 16

what are the units of k when the reaction order is 3

Answer 16

L^2/mol^2 * s

Question 17

in a first-order half-life, the half-life is ____ proportional to the k. And is ___ of the initial concentration

Answer 17

INVERSELY proportional
when k is large = fast reaction and it takes a smaller amount of time for the reaction to reach half of its life = t1/2
INDEPENDENT
- does not impact

Question 18

in a 2nd-order half-life, the half-life is ____ proportional to the [A] Initial. and is _____ proportional to the k

Answer 18

INVERSELY proportional
if you have a higher starting concentration amount you will have a smaller amount of time for the reaction to = half of its life
increasing concentration = increasing the rate = decreasing the half-life time
INVERSELY PROPORTIONAL

Question 19

in a zero-order half-life, the half-life is ____ proportional to the [A]initial. and is ___ proportional to k

Answer 19

DIRECTLY proportional to [A]
= [A]/2k
- the graph of the rate vs time = horizontal
when there is a high starting concentration (numerator) then it leads to a higher t1/2 = decays slow
INVERSELY proportional to k

Question 20

what is the collision theory

Answer 20

• particles need to have effective collisions, sufficient orientation and enough energy to react = transition state

Question 21

what factors (2) reduce the number of effective collisions

Answer 21

1. Activation energy
   - enough energy is needed to allow bond-breaking
   - to = transition state = Ea threshold
2. molecular orientation
   - molecules must have the appropriate orientation

Question 22

enthalpy

Answer 22

the total heat absorbed or released (exothermic or endothermic)
^H - Ea fwd - Ea rev
a reversible reaction has 2 activation energies - and the difference between = enthalpy of rxn

Question 23

transition state = activated complex?

Answer 23

yes
- species can change from reactants to products

Question 24

what is the effect of temp on the rate

Answer 24

inc temp = inc moving particles = inc collision freq = inc collision energy
temp affects collision frequency in a minor way because even if more collisions happen, do they have the right amount of energy to continue?
temp needs to increase the collision energy
it does not increase/decrease the Ea

Question 25

whats the difference between the reaction rate and the rate law

Answer 25

the rxn rate = a measure of how FAST rate law = shows how the rate is dependant on the reactant concentrations

Question 26

what does the Arrhenius Equation do

Answer 26

describes how the rate constant changes with temperature

Question 27

how are zero orders a real thing

Answer 27

the decomposition of ammonia DOES NOT depend on the concentration of the reactant - it depends on the surface area - so when it becomes saturated the rate doesn't increase or decrease but it makes the reaction rate constant

Question 28

what are elementary steps

Answer 28

when a reaction happens in multiple steps the elementary reactions add up to = an overall balanced equation - the common substances cancel out

Question 29

unimolecular

Answer 29

A --> B + C

Question 30

Bimolecular

Answer 30

A + B --> C

Question 31

Termolecular

Answer 31

2NO + O2 --> 2 NO2 3 reactants

Question 32

what is the rate-determining step

Answer 32

out of all the elementary steps, there is one slow reaction = rate-determining step - each separate reaction = own rate law expression but the slow one is the one that = entire reaction

Question 33

what is the reaction intermediate

Answer 33

A substance that is formed and used up during the overall reaction and therefore does not appear in the overall equation

Question 34

catalyst

Answer 34

A substance that increases the reaction rate without being consumed Provides a different reaction mechanism with a lower activation energy Low activation energy = higher rate Higher activation energy = lower rate

Question 35

Homogenous Catalyst

Answer 35

A gas, liquid or solid that exists in the same phase as the reactants

Question 36

Heterogeneous Catalyst

Answer 36

Speeds up a reaction in a different phase than the solution Ex: hydrogenation = adding hydrogen to a double-bonded carbon to make single-bonded carbons → speeds up reaction

Question 37

Explain how enzymes work

Answer 37

protein catalyst - active site that = shape as substrate - behaves like a hetero and homo catalyst - efficient with the number of rxn catalyzed per minute - enzymes usually catalyze only one type of rxn - induced fit model = active site changes to fit the substrate - enzyme-substrate complex (ES) - the enzyme and substrate = form a intermediate - the enzyme changes the orientation or breaks the bonds --> releases the substrate