Topic 16

Question 1

What can rate expressions also be called?

Answer 1

Rate law or rate equation

Question 2

What do rate expressions tell us?

Answer 2

The rate of a reaction as a function of the reactant concentrations

Question 3

What is the equation for rate?

Answer 3

Rate= K {A}x [B}y ( x and y are superscript)

• K= rate constant
• X= order of reaction with respect to A
• Y= order of reaction with respect to B

Question 4

What is K?

Answer 4

The rate constant

Question 5

How can the overall rate of a reaction be shown?

Answer 5

X+Y

Question 6

Write a balanced equation for the reaction of nitrogen monoxide and ozone and determine the rate expression

Answer 6

NO+ O3 –NO2+ O2
Rate = K[NO][O3]
- 1st order with respect to NO and O3

Question 7

How only can components of a rate expression be determined?

Answer 7

Experimentally

Question 8

What are the 3 aspects of determining the rate expression?

Answer 8

• Initial rates are calculated using concentration measurements
• The orders of a reaction are calculated using initial rates from several experiments
• Initial rate and orders of a reaction are used to calculate the value of the rate constant

Question 9

Describe elementary steps

Answer 9

• The reaction can happen in a series of steps

- The sequence of these steps are reaction mechanisms

Question 10

What does the rate of a reaction depend on?

Answer 10

The rate determining step which is the slowest

Question 11

What is a reaction intermediate?

Answer 11

An element that is produced in one step and consumed in another ( one on left hand side of equation, one on the right)

Question 12

What is the criteria for a reaction mechanism?

Answer 12

• The elementary steps must be reasonable ( unimolecular or biomolecular)
• the sum of the elementary steps must add up to the overall equation
• the rate expression of the rate determining step must be equal to the one calculated experimentally

Question 13

What do unimolecular equations have?

Answer 13

• One reactant particle

Question 14

What do bimolecular reactions have?

Answer 14

Two reactant particles

Question 15

What is the role of a catalyst?

Answer 15

Increases the rate of a chemical reaction by providing an alternative pathway with a lower activation energy

Question 16

What happens to the rate constant when activation energy is lowered?

Answer 16

Increases and alters the reaction mechanism

Question 17

What method is used to determine the order of a reaction?

Answer 17

The initial rates method

Question 18

What does it mean when the concentration of an element is doubled and the inital rate increases by a factor of 4?

Answer 18

THe reaction is 2nd order with respect to that element

Question 19

What happens when the concentration of an element is doubled and the intital rate is also doubled?

Answer 19

The reaction is 1st order with respect to that element

Question 20

What happens when changing the concentration has no effect on the rate of a reaction?

Answer 20

The reaction is zero order with respect to that element

Question 21

What does not appear in the overall chemical reaction?

Answer 21

The reaction intermmediates

Question 22

Draw an energy level diagram showing the transition states

Question 23

What exists between a reactant and product and forms an activated complex?

Answer 23

Transition states

Question 24

Draw a 1st order rate of reaction graph

Question 25

Draw a zero order rate of reaction graph