chapter 3

Question 1

What are the 4 main factors that influence the rate of reaction?

Answer 1

1. nature of reactants 2. concentration of reactants 3. temperature 4. catalysts

Question 2

as time goes on the rate of a reaction generally slows down because?

Answer 2

because the concentration of a reactant decreases

Question 3

instantaneous rate of reaction:

Answer 3

is the change in concentration at any one particular time

Question 4

is predicting the rate at some future time possible from just the balanced equation?

Answer 4

no

Question 5

Zero order:

Answer 5

rate is independent of the concentration of the reactant

Question 6

first order:

Answer 6

rate is directly proportional to the concentration of the reactants. So it slows down as the reaction proceeds.

Question 7

second order:

Answer 7

rate is proportional to the square of the concentration of the reactant

Question 8

the order of a reaction can be determined only by what?

Answer 8

experiment

Question 9

what are the unites for the rate constant for zero, first and second order?

Answer 9

zero order= M x s^-1 First order= s^-1 Second order= M^-1 x s^-1

Question 10

Left to right which graph represents first order, second order and zero order.

Answer 10

Question 11

Half life (t1/2)

Answer 11

is the time required for the concentration of a reactant to fall to one-half of its initial volume

Question 12

all radioactive decomposition follows ——- order kinetics

Answer 12

first

Question 13

half life in first order is independent of ———-

Answer 13

concentration

Question 14

An increase in temperature generally results in an increase in what?

Answer 14

k

Question 15

activation energy and activated complex:

Answer 15

amount of energy needed to convert reactants into the activated complex, aka transition state

Question 16

the higher the activation energy, the ——– the reaction rate

Answer 16

slower

Question 17

the exponential factor:

Answer 17

is a number betweeb 0 and 1 that represents the fraction of molecules that have enough energy to make it over the activation barrier on a given approach.

Question 18

collision model:

Answer 18

a chemical reaction occurs after a sufficiently energetic collision between 2 reactant molecules.

Question 19

orientation factor (p):

Answer 19

reacting molecules must collide in the proper oreintation for new bonds to form. Orientation is important!

Question 20

Reaction Mechanism:

Answer 20

is the series of individual chemical steps by which an overall chemical reaction occurs.

Question 21

each step in a reaction mechanism is called a what?

Answer 21

elementary step

Question 22

Reaction Intermediates:

Answer 22

species that form in one step of a mechanism and are consumed in another. A reaction intermediate is not found in the balanced equation for the overall reaction but plays a key role in the mechanism.

Question 23

Rate determining step or rate limiting step:

Answer 23

is much slower than the others. this step determines the rate of the overall reaction

Question 24

Catalysis:

Answer 24

a substance that increases the rate of a chemical reaction but is not consumed by the reaction

Question 25

what is a positive and negative catalyst?

Answer 25

positive catalysts speed up a reaction and negative catalysts slow down a reaction

Question 26

inhbitors are a what?

Answer 26

negative catalyst

Question 27

how do catalysts work?

Answer 27

by providing an alternative mechanism for the reaction

Question 28

what is the difference between homogenous and heterogenous catalysts?

Answer 28

homogenous exists in the same phase as the reactants where as heterogenous catyalysts exists in a different phase than the reacants

Question 29

they believe the ozone hole over the antartica is caused by what kind of catalyst?

Answer 29

heterogenous

Question 30

enzymes:

Answer 30

biological catalysts that increase the rates of biochemical reactions

Question 31

many heterogenous catalysts are deposited on high surface area supports. Why is a large surface area important for heterogenous catalysis?

Answer 31

heterogenous catalysysts require a large surfave area because catalysis can only happen at the surface. A greater surface area means greater opportunity for the substrate to react which results in a faster reaction.