GenChem5 (Kinetics and Equilibrium)

Question 1

A molecule in a mechanism that does not appear in the overall reaction because it is neither a reactant nor a product

Answer 1

intermediate

Question 2

The slowest step in a reaction is called the _____

Answer 2

rate determining step

Question 3

what are two definitions of the rate of a reaction?

Answer 3

decrease in reactants/time

increase in products/time

Question 4

In the reaction 2A + B —> C, relate all of the rates for each molecule

Answer 4

(-1/2)Δ[A]/Δt= -Δ[B]/Δt = Δ[C]/Δt

Question 5

A reaction that has a constant rate and is therefore independent of reactants’ concentrations is what type of reaction?

Answer 5

Zero-order reaction

Question 6

A reaction that has a rate that is proportional to one reactant is a

Answer 6

First order reaction

Question 7

Decay is what order of reaction?

What is the equation for radioactive decay?

Answer 7

First order

A=(Ao)e^-kt

Question 8

What is the equation for the half life of a reaction?

Answer 8

t(1/2) = ln(2)/k = 0.693/k

Question 9

A reaction that has a fractional order is called a

Answer 9

mixed order reaction

Question 10

A reaction with a rate proportional to the product of the concentration of two reactants or the square of the concentration of a single reactant is a

What are the units of second order rate constants

Answer 10

Second order reaction

M^-1)/(s^-1

Question 11

A reaction with an order greater than 2 is called a

Answer 11

higher order reaction

Question 12

Theory stating that the rate of a reaction is proportional to the number of collisions per second between the reacting molecules

Answer 12

Collision theory of chemical kinetics

Question 13

The minimum energy of collision necessary for a reaction to take place is called the

Answer 13

Activation energy, Ea, or energy barrier

Question 14

What is the rate in terms of number of collisions?

Answer 14

rate=fZ

Z= number of collisions, f= fraction of effective collisions

Question 15

A collision where molecules collide with the correct orientation and sufficient force to break the existing bonds and form new ones.

Answer 15

Effective Collision

Question 16

Occurs after a collision with sufficient energy, a state in which the old bonds are weakened and the new bonds begin to form

Answer 16

Transition state

Question 17

What is the other term for the transition state, which have an extremely short, finite lifetime?

Does it have a greater or lesser energy than the reactants/products?

Answer 17

Activated complex

It has a greater energy

Question 18

A negative enthalpy (ΔH) indicates what type of reaction?

A positive ΔH indicates what type of reaction?

Answer 18

Exothermic

Endothermic

Question 19

Where does the activated complex exist on a potential energy diagram?

Answer 19

At the top.

Question 20

What is the difference between the potential energy of the products and reactants?

Answer 20

ΔH, enthalpy change

Question 21

How does greater concentration of reactants affect the reaction rate?

Answer 21

Increases the rate

Question 22

How does higher temperature affect reaction rate?

Answer 22

Increases the rate (higher avg KE, more molecules with Ea)

Question 23

Can the medium effect the rate of the reaction?

Answer 23

Yes.

Question 24

Substances that increase the reaction rate without themselves being consumed

Answer 24

Catalysts

Question 25

How do catalysts affect the activation energy?

Answer 25

Catalysts lower the activation energy

Question 26

What is the equilibrium constant, Kc, for the following one step reaction:

2A=B+C

Answer 26

Kc=([B][C])/[A]^2

Question 27

If a reaction quotient, Q, is constant, what can be said about the reaction

Answer 27

It is in equilibrium, and Qc = Kc

Question 28

Do pure solids and liquids appear in the equilibrium constant?

Answer 28

No.

Question 29

Does Keq remain constant at different temperatures?

Answer 29

No.

Question 30

If Keq is much larger than 1, are there more reactants or products?

Answer 30

Products

If less than one, more reactants

Question 31

If Keq is close to one, what can be said about products and reactants?

Answer 31

They are equal and approximately in equilibrium

Question 32

Does changing the pressure affect the volume of all substances?

Answer 32

No, mainly gases because they are highly compressible

Question 33

How are pressure and volume related?

Answer 33

Inversely

Question 34

In the following system:

A–>B + heat

What would happen if it were placed in an ice bath?
What about if it were placed in boiling water?

Answer 34

The temperature would decrease and equilibrium would shift to the right

Equilibrium would shift to the left

Question 35

What is the only thing that can alter the equilibrium constant of a reaction?

Answer 35

Temperature. Not concentration, pressure, volume, etc.