Chapter 5 Thermochemistry

Question 1

Heat:

Answer 1

The energy transferred between objects because of a difference in their temperatures

Question 2

Work:

Answer 2

A form of energy: the energy required to move an object through a given distance
W = F x d
W = -P (change in) V {{NEGATIVE}}

Question 3

What are the types of work?

Answer 3

Electrical (battery, voltaic), mechanical (using chemical energy, P(Vf-Vi)), Light (battery electrolysis), sound energy (force -> vibration)

Question 4

Potential Energy:

Answer 4

The energy stored of an object because of its position. Function of position. PE = m x g x h
-it is a state function
-at greatest height, greatest PE
-always trying to get to lowest PE

Question 5

State function:

Answer 5

Only the initial and final conditions matter (ie straight up mountain = PE to zig zag up mountain)
-no motion KE = 0

Question 6

Kinetic Energy:

Answer 6

The energy due to motion of an object. Function of motion. KE = 1/2mv^2

Question 7

Energy at the molecular level:

Answer 7

PE: Electrostatic energy, repulsion (increasing -PE), optimal distance, attraction (decreasing -PE), no interaction
Eel proportional to Q1 x Q2/d
KE: mass, velocity, temperature

Question 8

Endothermic and exothermic reactions with phase change:

Answer 8

Exo : Condensation, freezing, deposition
Endo : Melting, vaporization, sublimation

Question 9

System:

Answer 9

The part of the universe that is the focus of a thermochemical study

Question 10

What are the types of systems?

Answer 10

Isolated: no energy or matter exchange
Closed: Energy exchange, no matter exchange
Open: Energy and matter exchange

Question 11

Surrounding:

Answer 11

Everything in the universe that is not part of a system

Question 12

Internal energy:

Answer 12

Is a state function, it is the sum of KE and PE of all components in system. Three types are translational, rotational, and vibrational
Change in E = q + w = q + -P (change in)V

Question 13

What are the units of energy?

Answer 13

Calorie (cal): amount of heat necessary to raise the temp of 1 g of water by 1 C
Joule (J): The SI unit of energy, 4.184 J = 1 cal

Question 14

What is the key to an internal energy equation?

Answer 14

What are the signs of q and w

Question 15

When work is done by the surroundings what is happening to the volume, what is the sign of w, what happens to the internal energy, and what are the possible signs of q?

Answer 15

Volume is decreasing, “work is done on the system”
w = +
increase in internal energy
q: E released q = -, absorbed q = + (heating)

Question 16

When work is done by the system what is happening to the volume, what is the sign of w, what happens to the internal energy, and what are the possible signs of q?

Answer 16

Volume is increasing “work is done on the surroundings”
w = -
decrease in internal energy
q: E released q = -, absorbed q = + (heating)

Question 17

What is change in H?

Answer 17

It is equal to q, but is for specific processes

Question 18

What are the changes in H of rxns

Answer 18

fusion: s –> l
vaporization: l –> g
condensation: g –> l
solidification: l –> s

Question 19

What is the relationship between temperature and kinetic energy at the molecular level?

Answer 19

Temperature is proportional to kinetic energy