Chapter 6: Thermochemistry- Part 1

Question 1

What is energy?

Answer 1

The ability to transfer heat
The ability to do work

Question 2

Work

Answer 2

Symbol: W
W=(force)x(distance)

Question 3

Major Types of Energy?

Answer 3

PE and KE

Question 4

Potential Energy

Answer 4

-It is associated with position
-No one equation for calculating PE

Question 5

Kinetic Energy

Answer 5

-Associated with motion
-Formula KE=1/2mv^2
-M(mass) express in kg
V(velocity) express in m s-1

Question 6

Problem: What is the kinetic Energy in kg m^2 s^-2, of a baseball (145.5g) moving at 144.841 km hr^-1?

Answer 6

145.5g=0.1455kg
(144.841km hr-1)(1000m/1km)(1hr/3600sec)=40.23m/s
KE=1/2(0.1455kg)(40.23m/s)^2
117.8 kg m^2 s^-2

Question 7

Heat (thermal energy)

Answer 7

-Energy usually associated with temperature changes…
-Also associated with molecular/atomic motion

Question 8

Other forms of energy?

Answer 8

~Electrical
~Solar
~Nuclear
~Geothermal
~Chemical

Question 9

Law of Conservation of Energy contain?

Answer 9

1st law of thermodynamics
Systems
Surroundings
Enthalpy

Question 10

What is system?

Answer 10

Limited portion of the world that we are interested in.

Question 11

What is surroundings?

Answer 11

Everything else e.g. the universe

Question 12

Energy movement is defined in terms of the system and surroundings.

Answer 12

Exothermic processes
Endothermic processes

Question 13

Exothermic processes

Answer 13

Energy moving from the system to the surroundings.

Question 14

Endothermic processes

Answer 14

Energy moving from the surroundings to the system.

Question 15

What is the state function?

Answer 15

A property that is dependent only on the current condition and is independent of how it arrived at that condition.
E.g. altitude, temperature

Question 16

What is the 1st Law of thermodynamics?

Answer 16

States that energy is neither created nor destroyed can only be shifted from one form to another.

Question 17

What is a energy for a system, E total made of?

Answer 17

It is made up of microscopic kinetics and potential energy as well as microscopic kinetic and potential energy components.

Question 18

E total formula

Answer 18

Etotal= KE+ PE + U

Question 19

Where KE

Answer 19

Macroscopic Kinetic Energy Components

Question 20

Where PE is

Answer 20

macroscopic potential energy components

Question 21

Where U

Answer 21

Internal energy (microscopic components)

Question 22

Measuring E total directly is very difficult (e.g. impossible in most cases), so we look at changes is energy rather than absolute energies

Answer 22

DeltaE=E final-E start
DeltaE= products -E reatants

Question 23

System formula

Answer 23

U system= q + w

Question 24

What does q means?

Answer 24

Heat component

Question 25

What does w means?

Answer 25

Work component

Question 26

Information in q= “+”

Answer 26

Heat is imported into the systems e.g., an endothermic process

Question 27

Information q= “-“

Answer 27

Heat is exported from the system, e.g., and exothermic process

Question 28

Information w= “+”

Answer 28

If the surroundings does work on the systems (imports work)

Question 29

Information w= “-“

Answer 29

If the system does work o the surroundings (exports work)

Question 30

Heat Capacity

Answer 30

A) the amount of heat (ENERGY) needed to change thee temperature of an object by 1C or 1K.
B) used most often with objects. Heat capacity is dependent on sample size.
C) heat capacity= energy J/Delta temp (c or K)

Question 31

Problem: An alumimun part took 161 J of energy to raise its temperature from 22.3 C to 28.9C. What is the heat capacity of the aluminum part?

Answer 31

161 J/28.9-22.3
=24.4 J C^-1

Question 32

What is specific heat capacity, Cp?

Answer 32

A) It is the amount of heat to change the temp of a given mass of material by 1C or 1K
B) Cp= energy J / (mass)(temp) or q / mass temp)

Question 33

C) Problem: How much heat is needed to raise the temp of 11.65g of copper from 22.10 C to45.06C? (For Cu Cp= 0.384 J g^-1 C^-1)

Answer 33

0.384 J q^-1 C^-1= ?q / (11.65g)(22.96C)
- q=(0.384 J g^-1 C-1)(11.65g) (22.96C)
=103 J

Question 34

What is molar heat capacity?

Answer 34

A) It is the amount of heat need to change the temp of a mole of material by 1C or 1K
B) mola heat capacity= energy J / 1 mole temp or q/ J T
C) molar heat capacity = (specific heat capacity) (molar mass)

Question 35

D) problem: What is the molar heat capacity of Copper?

Answer 35

Molar heat capacity= (0.384 J g^-1 C^-1) (63.55 g mole^-1)
=24.4 J mole^-1 C^-1