Chpt 14: Chemical Kinetics

Question 1

what is an integrated rate law?

Answer 1

expressions for reaction rate that integrate concentration AND time

Question 2

what is a Heterogeneous catalyst?

Answer 2

A rxn catalyst that is in a different phase than the reactants

Question 3

why can’t stoichiometry be used to determine the rate order of a chemical reaction?

Answer 3

because stoichiometry reflects the overall net reaction being examined, but does not account for any of the elementary reactions required to produce the overall net reaction

Question 4

does each reactant in a rate law have its own rate order?

Answer 4

yes

Question 5

4 factors that effect chemical reaction rates

Answer 5

1. Physical state of reactants
2. concentration
3. Temperature
4. Presence of catalysts

Surface area of atoms makes a difference, too. Thanks, Khan!

Question 6

what are the units for a zero order reaction’s rate constant?

Answer 6

M/s

Question 7

what are the 3 types of molecularity

Answer 7

1. Unimolecular
2. Bimolecular
3. Termolecular

Question 8

which mathematical description of reaction rates uses reaction stoichiometry?

Answer 8

basic reaction rate

Question 9

how are integrated rate laws different from ‘regular’ rate laws?

Answer 9

integrated rate laws let you determine/compare specific concentrations at specific times

Question 10

what does the slope tell you in a zero order graph of [M] vs time?

Answer 10

-k constant

Question 11

what does the slope tell you in a second order graph of 1/[M] vs time?

Answer 11

k

Question 12

how are instantaneous reaction rates approximated?

Answer 12

the slope of a point on a graph of delta concentration vs delta time

Question 13

on a rxn energy profile (where elementary steps are involved), are transition states shown as humps or dips?

Answer 13

humps

energy spikes as activation complex forms, then drops as reaction proceeds

Question 14

when examining reaction rates, what is a tangent line used for?

Answer 14

A tangent line can be placed along the graph, through a particular point in time (along the x axis), and the tangent line’s slope can be calculated to provide the instantaneous rate for the selected time point

Question 15

what does a Negative catalyst do?

Answer 15

Slow down rxns

Question 16

which order of integrated rate law expression involves ln [M] values?

Answer 16

first order

Question 17

what 2 factors are k constants dependent upon in the Arrhenius eqn?

Answer 17

frequency factor and activation energy

Question 18

what is ‘chemical Kinetics’ the study of?

Answer 18

study and discussion of how reactions progress, particularly with regard to reaction rates/speeds

Question 19

what is the equation for a basic reaction rate

Answer 19

delta concentration/delta time

Question 20

which type of reaction rate expression employs instantaneous and average rates?

Answer 20

basic reaction rates

Question 21

how are average reaction rates approximated?

Answer 21

with delta concentration/delta time

Question 22

on a rxn energy profile (where elementary steps are involved), are intermediates shown as humps or dips?

Answer 22

dips

intermediates are formed right after activation complexes [shown as humps] resolve

Question 23

do products get written into reaction rate expressions?

Answer 23

no.

Question 24

what range of K constant values indicate that a reaction is relatively fast?

Answer 24

values equal to 10^9 or bigger

Question 25

in math r/t rates, how can you 'bring a number down' from the exponents?

Answer 25

'take the ln' of the value in the exponent. You have to do this to all terms on both sides of the equation

Question 26

what are the units for a first order reaction's rate constant?

Answer 26

s-1 or 1/s

Question 27

when we say 'initial rate', what are we actually referring to?

Answer 27

the rate of a reaction at any given point in time (as shown on a graph)...because chemists don't speak English...😒

Question 28

which mathematical description of reaction rates uses the concept of 'reaction order'?

Answer 28

rate law and integrated rate law

Question 29

which order of integrated rate law expression involves [M] values?

Answer 29

zero order

Question 30

what is an 'average reaction rate' the average of?

Answer 30

reaction's initial rates, over a specified period of time

Question 31

what does the slope tell you in a first order graph of ln [M] vs time?

Answer 31

-k

Question 32

how does Adsortion occur (in the context of catalysts' participation in chemical reactions)?

Answer 32

reacting molecules bind to the surface of a catalyst, and this lowers the activation energy

Question 33

which order of integrated rate law expression involves 1/[M] values?

Answer 33

second order

Question 34

in math r/t rates, how can 'cancel' an 'ln' in your equation???

Answer 34

raise "e" to the expression with the ln in it??? You have to do this to all terms on both sides of the equation

Question 35

what is the difference between a reaction 'transition state' and a reaction 'intermediate'?

Answer 35

A reaction 'intermediate' is a compound that is created and then immediately consumed as part of a rate mechanism. A reaction 'transition state' is what you call two molecules (who have collided and become distorted) right before they react with one another

Question 36

How is rate order determined in rate laws and integrated rate laws?

Answer 36

by doing experiments

Question 37

what does a reaction mechanism describe?

Answer 37

the steps that occur over the course of a rxn

Question 38

what is the difference between an intermediate product and a catalyst?

Answer 38

an intermediate gets made and then consumed during the elementary reactions. Catalysts don't get consumed by the reaction

Question 39

what does a basic reaction rate depend on (mathematically)?

Answer 39

The disappearance of reactants or the appearance of products with respect to time, given by the reaction's stoichiometry

Question 40

what does the Arrhenius Equation relate?

Answer 40

Relates quantities of collision model: frequency factor, activation energy, and k constant AT A GIVEN TEMPERATURE

Question 41

what does Beer's Law state?

Answer 41

Says the absorption of radiation (at a given wavelength) by a substance is proportional to the solution's concentration We used this concept with the spectroscope in biology class when she shined the light on the reaction to measure the enzyme activity in the starch

Question 42

what is a 'rate law' rate expression?

Answer 42

a mathematical expression that describes rate of rxn in terms of concentrations and time

Question 43

Do reaction rates get faster or slower over time?

Answer 43

they get slower over time as reactants start to run out (evidenced by decreased reactant concentration)

Question 44

what kind of graph results from a zero order plot of [M] vs time?

Answer 44

a straight line going down

Question 45

what range of k constant values indicate that a reaction is relatively slow?

Answer 45

values smaller than 10^9

Question 46

which type of reaction rate expression employs INITIAL rates?

Answer 46

rate laws and integrated rate laws

Question 47

what is an Active site?

Answer 47

The complex on an enzyme where catalysis is facilitated

Question 48

how do catalysts reduce activation energy?

Answer 48

by introducing an alternative rate reaction for the overall/net reaction

Question 49

what is an Intermediate 'product' in a rate mechanism?

Answer 49

Temporary/intermediate product created during a former elementary rxn/step that gets consumed in the process of the rxn progressing to the next elementary rxn/step

Question 50

what branch of mathematics explains the expressions for rate laws and rate orders?

Answer 50

calculus

Question 51

what kind of graph results from a second order plot of 1/[M] vs time?

Answer 51

straight line going UP

Question 52

what does the Lock and Key model for enzymes describe?

Answer 52

The idea that substrates bind to enzymes at specific active sites in order to initiate the rxn

Question 53

what 2 factors are k constants generally dependent upon?

Answer 53

temperature | presence of catalysts

Question 54

What is an activated complex?

Answer 54

The region between/around molecules/compounds that are about to bond in a reaction Occurs when the rxn molecules/compounds are in a high energy/transition state; about to react

Question 55

what kind of graph results from a first order plot of ln [M] vs time?

Answer 55

a straight line gown down

Question 56

how are the rate laws for elementary reactions determined?

Answer 56

by their molecularity: The number of REACTANT molecules present during a given step/elementary rxn of an overall chemical rxn

Question 57

what are the units for a second order reaction's rate constant?

Answer 57

M-1 s-1 or 1/M*s

Question 58

what are Substrates?

Answer 58

What you call the reactants that enzymes act on

Question 59

What are the three ways to mathematically describe the rate/speed of a chemical reaction?

Answer 59

(basic) Reaction rate Rate Law Integrated rate law

Question 60

what does a reaction rate quantify?

Answer 60

the speed at which a chemical reaction occurs

Question 61

what is a Rate determining step (of a rxn mechanism)?

Answer 61

The slowest in a series of rxn elementary steps Sets the pace for the entire over arching rxn; often involves intermediate 'products'

Question 62

what are Enzymes?

Answer 62

biological catalysts that facilitate 'catalysis' (speed up reactions) in living things

Question 63

what is a Homogenous catalyst?

Answer 63

A rxn catalyst that is in the same phase as the reactants

Question 64

what kind of graph results from a first order plot of [M] vs time?

Answer 64

some kind of downward curve

Question 65

what is Activation energy?

Answer 65

the Minimum energy required for a rxn to occur