Chapter Five: Thermochemistry

Question 1

What is the study of energy and its transformations among potential energy, heat and work?

Answer 1

Thermodynamics

Question 2

What is the relationship between chemical reactions and energy changes?

Answer 2

Thermochemistry

Question 3

W = what times what

Answer 3

F x d

Question 4

Work is done when a gas __________ against an opposing pressure

Answer 4

expands

Question 5

Work is done by a force acting in a given direction. In lifting a weight, the energy is stored as gravitational….

Answer 5

Potential energy

Question 6

This is the part of the universe that we are studying. Define as a certain amount of matter, or a certain region of space

Answer 6

The System

Question 7

The matter or space that lies outside the system. Usually only that matter, or space, that is affected by the system

Answer 7

The surroundings

Question 8

What kind of system?
- both matter and heat can flow in or out

Answer 8

Open System

Question 9

What kind of system?
- heat can flow in or out, but not matter

Answer 9

Closed System

Question 10

What kind of system?
- neither heat or matter can flow in or out

Answer 10

Isolated System

Question 11

The universe = what plus what

Answer 11

system + surroundings

Question 12

Energy transferred as heat can either (1) increase the ___________ or (2) change the _________ of a substance (solid,liquid,gas)

Answer 12

Temperature
Phase

Question 13

The measure of the speed at which atoms or molecules are moving, heat is a measure of the Kinetic Energy that is transferred

Answer 13

Temperature

Question 14

Most chemical reactions is mainly associated with what kind of energy?

Answer 14

Potential Energy

Question 15

A system possesses its potential energy by virtue of its position, configuration, or chemical…

Answer 15

composition

Question 16

energy due to mass in motion

Answer 16

Kinetic Energy

Question 17

Energy can be (1) transformed (from PE to KE), and (2) transferred (from one object to another) but (3) is neither…

Answer 17

created nor destroyed

Question 18

What is this?
- when energy is transferred to the spring, and stores as potential energy
- ∆V = -
- W = -P∆V
- ∆E = +

Answer 18

Compression

Question 19

What is this?
Energy is transferred to the ball as Kinetic Energy
- ∆V = +
- W = -P∆V
- ∆E = -

Answer 19

Expansion

Question 20

What is the amount of heat required to raise the temperature of 1.00 g of a substance by 1.00 degrees celsius?

Answer 20

Specific Heat (Cs)

Question 21

• Heat transferred to the system
• The surroundings get colder
• Work is done on system by the surrounding
• Everything is positive
  Is this a deposit or withdrawal?

Answer 21

Deposit - compression

Question 22

• Heat transferred to the system
• The surroundings get hotter
• Work done by the system on surroundings
• Everything is negative
  Is this a deposit or a withdrawal?

Answer 22

Withdrawal - expansion

Question 23

What kind of function?
- If the system undergoes a ∆, the ∆ in the property can be determined as long as you know the initial and final states

Answer 23

State functions

Question 24

What kind of function?
- If the system undergoes a ∆, the ∆ in the property cannot be determined by knowing the initial and final states. In this case, one must also know the exact pathway of change

Answer 24

Path Funcitons

Question 25

What property?
- a property that depends on the amount of sample you consider
- Mass
- Volume

Answer 25

Extensive Property

Question 26

What property?
- a property that does not depend on the amount of sample you consider
- density
- temperature

Answer 26

Intensive Property

Question 27

The heat transferred in a process that occurs at _____________ _____________ is also a state function. It is called the change in enthalpy and symbolized by ∆H

Answer 27

Constant Pressure

Question 28

Change in enthalpy is symbolized by…

Answer 28

∆H

Question 29

The _____________ of ______________ or the heat of reaction is the energy released as heat when a reaction is done in an open container (at constant atmospheric pressure)
∆H reaction

Answer 29

enthalpy of reaction

Question 30

When ∆H is positive, heat goes from the surroundings to the system. Is this endothermic or exothermic?

Answer 30

Endothermic

Question 31

When ∆H is negative. Heat goes from the system to the surroundings. Is this endothermic or exothermic?

Answer 31

Exothermic

Question 32

Every reaction can be thought of as occurring in what two steps?

Answer 32

1. take the reactants apart to form elements
2. reform the elements into products

Question 33

Enthalpy Facts:
1. ∆H rxn depends on the (a) ___________ state of the products and (b) the ______________

Answer 33

physical
reactants

Question 34

Enthalpy Facts:
2. Enthalpy, is an ____________ property (If I burn twice the amount of wood, I get twice the heat)

Answer 34

extensive

Question 35

Enthalpy Facts:
3. ∆H rxn in the forward direction is equal in size but opposite in…

Answer 35

sign

Question 36

Enthalpy Facts: Hess’ Law
4. Because enthalpy is a state function, ∆H rxn that happens in two or more steps can be found by __________ ∆H’s for each of those reaction steps

Answer 36

adding