Unit 3: Energy Changes and Rates of Reactions

Question 1

Chemical Kinetics

Answer 1

The area of chemistry that deals with rates of reactions

Question 2

Rate of reaction/reaction rate is obtained by…

Answer 2

Measuring

Question 3

Whats the average reaction rate equation?

Answer 3

r = △C/ △t

Question 4

Simple Reactions

Answer 4

Take place in one elementary step (bimolecular)

Question 5

Complex Reactions

Answer 5

• Take place in a series of steps (mechanism) which adds up to the same net equation
• Each step has its own activation energy that must be reached. Complex reaction mechanisms contain reaction intermediatics
• These are products of one reaction that immediately become reactions in another reaction
• Reaction intermediates do not appear in the net reactions

Question 6

Thermochemistry

Answer 6

The study of the energy changes that accompany physical or chemical changes in matter

Question 7

Physical Change + Example

Answer 7

Change in the arrangement of the molecules

Example: Hydrogen boils at -252 degrees

Question 8

Chemical Change+ Example

Answer 8

Change in electronic structure

Example: Hydrogen is burned as fuel in space shuttles

Question 9

Nuclear Change+ Example

Answer 9

Change in the nuclei of the atoms

Example: Hydrogen undergoes nuclear fusion in the sun producing helium

Question 10

Exothermic (-)

Answer 10

Energy leaves the system

Question 11

Endothermic (+)

Answer 11

Energy enters the system

Question 12

Open System

Answer 12

Matter and energy can move in/out of the system

Example: Burning marshmallow

Question 13

Closed System

Answer 13

Energy can move in/out but not matter

Example: Styrofoam cup

Question 14

Isolated System

Answer 14

Ideal system; Neither matter or energy can move in/out

Example: Bomb Calorimeter

Question 15

Calorimetry

Answer 15

The technological process of measuring energy changes in a chemical system

Question 16

What are the 3 factors that are combined in an equation to represent the quantity of heat (q) transferred?

Answer 16

1) Mass
2) Type of substance (c); specific heat capacity
3) Temperature Change △T

Question 17

What are the two equations for calculating energy changes?

Answer 17

1) q=mc △T

2) △T= T2-T1

Question 18

Specific Heat Capacity

Answer 18

The quantity of heat required to raise the temperature of a unit mass of a substance by one degree

Question 19

Enthalpy Change (△H)

Answer 19

The difference in enthalpies of reactions and products during a change

Question 20

Law of Conservation of Energy

Answer 20

The total energy change of the chemical system is equal to the total energy change of the surroundings

Question 21

What are the 3 types of enthalpy change?

Answer 21

1) Physical Change
2) Chemical Changes
3) Nuclear Changes

Question 22

Molar Enthalpy (△Hx)

Answer 22

The enthalpy change associated with a physical, chemical, or nuclear change involving one mole of a substance (kJ/mol)

Question 23

What is the equation used to find molar enthalpy?

Answer 23

△H= n△H

Question 24

What are the 3 assumptions made when using calorimetry?

Answer 24

1) no heat is transferred between the calorimeter and the outside environment
2) Any heat absorbed or released by the calorimeter materials is negligible
3) Dilute aqueous solutions are assumed to have a density and specific heat capacity equal to that of pure water

Question 25

What is the equation that is the combination of the 2 previously learned energy change equations?

Answer 25

n △Hx=mc △T

Question 26

What are the 4 different ways to represent an enthalpy change? + Example

Answer 26

1) By including an energy value as a term in the thermochemical equation
Ex: CH3OH + 3/2 O —-> CO2 + 2H20 + 726 KJ
2) By writing a chemical equation and stating its enthalpy change
Ex: CH3OH + 3/2O —–> CO2 +2H20
3) By stating the molar enthalpy of a specific reaction
Ex: △H combustion or △Hc= -726 KJ/mol CH3OH
4) By drawing a chemical potential diagram

Question 27

Review Rates of Reactions

Answer 27

.

Question 28

Review Rate Laws and Order of Reaction

Answer 28

.

Question 29

Review Collision Theory and Rate of Reaction

Answer 29

.

Question 30

Review Reaction Mechanisms

Answer 30

.

Question 31

Review Kinetics Practice Assignment

Answer 31

.

Question 32

Review Molar Enthalpies

Answer 32

.

Question 33

Review Enthalpy Changes; Point 4

Answer 33

.

Question 34

Review Hess’s Law of Additivity of Reaction Enthalpies

Answer 34

.