Unit 5: Chemical Kinetics

Question 1

What is chemical kinetics?

Answer 1

The study of how fast chemical reactions occur.

Question 2

What does a reaction rate measure?

Answer 2

Change in concentration over time.

Question 3

How is average rate calculated?

Answer 3

Change in concentration divided by change in time.

Question 4

How is instantaneous rate determined?

Answer 4

By the slope of a tangent to the concentration vs. time curve.

Question 5

Why are reaction rates important?

Answer 5

They help control industrial processes, biological functions, and safety.

Question 6

How are reaction rates expressed?

Answer 6

In mol/L·s or M/s.

Question 7

How is the rate of a reactant written?

Answer 7

As a negative change in concentration over time.

Question 8

How is the rate of a product written?

Answer 8

As a positive change in concentration over time.

Question 9

What factors affect reaction rates?

Answer 9

Identity of reactants, temperature, concentration, surface area, and catalysts.

Question 10

How does temperature affect reaction rate?

Answer 10

Generally, it increases rate by increasing kinetic energy.

Question 11

What is a rate law?

Answer 11

An equation that shows how rate depends on reactant concentrations.

Question 12

What is the rate constant (k)?

Answer 12

A proportionality constant specific to a reaction and temperature.

Question 13

What is the unit of k for a first-order reaction?

Answer 13

1/s.

Question 14

What is the unit of k for a second-order reaction?

Answer 14

1/(M·s).

Question 15

What is the unit of k for a zero-order reaction?

Answer 15

M/s.

Question 16

How is reaction order determined?

Answer 16

Experimentally, usually by the method of initial rates.

Question 17

What is a zero-order reaction?

Answer 17

A reaction whose rate does not depend on reactant concentration.

Question 18

What is a first-order reaction?

Answer 18

A reaction whose rate is proportional to the concentration of one reactant.

Question 19

What is a second-order reaction?

Answer 19

A reaction whose rate is proportional to the square of one reactant or the product of two.

Question 20

What is the overall order of a reaction?

Answer 20

The sum of the exponents in the rate law.

Question 21

What is an integrated rate law?

Answer 21

An equation that shows how concentration depends on time.

Question 22

What is the integrated rate law for a first-order reaction?

Answer 22

ln[A] = -kt + ln[A]₀.

Question 23

What is the integrated rate law for a second-order reaction?

Answer 23

1/[A] = kt + 1/[A]₀.

Question 24

What is the half-life of a reaction?

Answer 24

Time required for the concentration of a reactant to decrease by half.

Question 25

How does half-life behave in a first-order reaction?

Answer 25

It is constant.

Question 26

How does half-life behave in a second-order reaction?

Answer 26

It depends on initial concentration.

Question 27

What is collision theory?

Answer 27

A model that explains reaction rate as dependent on collisions between reactant particles.

Question 28

What is activation energy (Ea)?

Answer 28

The minimum energy required for a reaction to occur.

Question 29

What is the Arrhenius equation?

Answer 29

k = Ae^(-Ea/RT), relating rate constant to activation energy.

Question 30

How does a catalyst affect a reaction?

Answer 30

It increases the rate by lowering the activation energy.

Question 31

What is a reaction mechanism?

Answer 31

A sequence of steps that describe how a reaction occurs.

Question 32

What is the rate-determining step?

Answer 32

The slowest step in a reaction mechanism.

Question 33

What is an intermediate?

Answer 33

A species formed and consumed during a reaction mechanism.