Chemistry Chemical Kinetics

Question 1

The ___ of a chemical reaction is the actual series of steps through which it occurs

Answer 1

mechanism

Question 2

The slowest step in a proposed mechanism is called the rate-determining step, because the overall ___ cannot proceed faster than that step

Answer 2

reaction

Question 3

___ is the study of the rates (or speed) of reactions

Answer 3

chemical kinetics

Question 4

The ___ is the change of concentration of reactant or finished product with respect to time

Answer 4

reaction rate

Question 5

Reactants -> Products
This equation indicates that ___ molecules are being consumed (concentration decreases) and the product molecules are being formed (concentration increases)

Answer 5

reactant

Question 6

The process of chemical kinetics is concerned with how “fast” the ___ are being transformed into products

Answer 6

reactants

Question 7

rate = decrease in concentration of ___/time = increase in concentration of products/time

Answer 7

reactants

Question 8

Because the ___ of a reactant decreases during the reaction, a minus sign is placed before a rate that is expressed in terms of reactants

Answer 8

concentration

Question 9

For the reaction 2A + B yields C:
The rate of reaction with respect to A is -(delta[A]/delta t)
with respect to B is -(delta[B]/delta t),
and with respect to C is (delta[C]/delta t)
___ is expressed in the units of moles per liter per second (mol/[Lxs) or molarity per second (molarity/s)

Answer 9

rate

Question 10

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

This expression is the ___ for the general reaction above, where k is the rate constant

Answer 10

rate law

Question 11

The ___ is defined as a constant of proportionality between the chemical reaction rate and the concentration of the reactants

Answer 11

rate constant

Question 12

The ___ x and y are called the orders of reaction; x is the order with respect to A, and y is the order with respect to B

Answer 12

exponents

Question 13

It is important to note that the ___ of the rate law are not necessarily equal to the stoichiometric coefficients in the overall reaction equation

Answer 13

exponents

Question 14

The exponents are equal to the ___ coefficients of the rate-determining step

Answer 14

stoichiometric

Question 15

The overall order of a ___ (or the reaction order) is defined as the sum of the exponents, here equal to x + y

Answer 15

reaction

Question 16

A zero-order reaction has a constant rate, which is independent of the ___ concentrations

Answer 16

reactants

Question 17

A first-order ___ has a rate proportional to the concentration of one reactant.
rate = k[A] or rate = k[B]

Answer 17

reaction

Question 18

A second-order reaction has a rate proportional to the ___ of the concentration of two reactants or to the square of the concentration of a single reactant

Answer 18

product

Question 19

The ___ states that the rate of a reaction is proportional to the number of collisions per second

Answer 19

collision theory of chemical kinetics

Question 20

It is important to note that ___ almost always increase with increasing temperatures. On the other hand, reaction rates decrease with decreasing temperatures

Answer 20

reaction rates

Question 21

An ___ (one that leads to the formation of products) occurs only if the molecules collide with the correct orientation and sufficient force to break the existing bonds and form new ones

Answer 21

effective collision

Question 22

The minimum energy of collision necessary for a reaction to take place is called the ___ E sub a, or the energy barrier

Answer 22

activation energy

Question 23

Only a fraction of colliding ___ have enough kinetic energy to exceed the activation energy. This means that only a fraction of all collisions are effective

Answer 23

particles

Question 24

When molecules collide with sufficient energy and in the correct orientation, they form a ___ in which the old bonds are weakened and the new bonds are beginning to form

Answer 24

transition state

Question 25

The ___, also called the activated complex, has greater energy than either the reactants or the products and is denoted by a symbol

Answer 25

transition state

Question 26

The activation energy is required to bring the reactants to this particular ___ level

Answer 26

energy

Question 27

Once an activation complex is formed, it can either dissociate into the ___ or revert to reactants without any additional energy input

Answer 27

products

Question 28

___ are distinguished from intermediates in that, existing as they do at energy maxima, transition states do not have a finite lifetime

Answer 28

transition states

Question 29

A ___ illustrates the relationship between the activation energy, the heats of reaction, and the potential energy of the system before and after the reaction. The most important factors in such diagrams are the relative energies of the products and reactants. The enthalpy change of the reaction (delta H) is the difference between the potential energy of the products and the potential energy of the reactants. A negative enthalpy change indicates an exothermic reaction (where heat is given off), and a positive enthalpy change indicates an endothermic reaction (where heat is absorbed)

Answer 29

potential energy diagram

Question 30

The ___ exists at the top of the energy barrier

Answer 30

activated complex

Question 31

The difference in ___ between the activated complex and the reactants is the activation energy of the forward reaction; the difference in potential energies between the activated complex and the products is the activation energy of the reverse reaction

Answer 31

potential energies

Question 32

Consequently, the proportion of ___ having energies greater than E sub a (and thus capable of undergoing reaction) increases with higher temperature

Answer 32

molecules

Question 33

Therefore, the presence of a ___ causes the reaction to proceed more quickly toward equilibrium

Answer 33

catalyst