Chapter 9

Question 1

What is the principal source of energy on earth?

Answer 1

The sun introduces energy onto the earth and drives wind and water cycles.

Question 2

Thermochemistry

Answer 2

thermochemistry: the energy changes that occur during chemical & physical changes

Question 3

Energy

Answer 3

the capacity to do work or transfer heat

Question 4

Work (w):

Answer 4

the action of a force applied across a distance

Question 5

Heat (q)

Answer 5

transfer of energy from a hotter or colder
object

Heat flows from a hotter object in contact with a colder object until they are the same temp

Question 6

Kinetic energy:

Answer 6

energy of objects in motion

Question 7

Potential energy

Answer 7

energy of an object by virtue
of its position or composition

Question 8

Thermal energy

Answer 8

Kinetic energy (or thermal energy) is the energy associated with the random motion of atoms and molecules.

Question 9

Electromagnetic energy

Answer 9

energy carried through space by electromagnetic waves

Question 10

Law of Conservation of
Energy

Answer 10

energy can be neither
created nor destroyed; it is
converted from one form to
another

Question 11

calorie (cal)

Answer 11

1 cal = 4.184 J (exactly)

Question 12

State function

Answer 12

values that depend on the state of the substance, and not on how that state was reached. It is path independent

Question 13

Hess’s law

Answer 13

If a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes of the various steps

Question 14

Is temperature potential or thermal energy?

Answer 14

• Temperature: a quantitative measure of thermal energy
• Temperature of a gas is directly proportion to the average kinetic energy (Kinetic Molecular Theory)

Question 15

exothermic process

Answer 15

Chemical/physical change that releases heat

Heat is negative
Think about the system and define it

Question 16

endothermic process

Answer 16

Chemical/physical change that absorbs heat

Heat is positive

Question 17

Molar heat capacity

Answer 17

Heat capacity per mol

-used when talking about pure substance’s homogenous

Question 18

heat capactiy

Answer 18

the amount of heat needed to raise the temperature by 1K/1 °C

then be used for objects and any type of mixture

Question 19

Specific heat capacity

Answer 19

heat capacity per gram

can be used for heterogenous mixtures or homogenous mixtures

Question 20

Calorimetry and types

Answer 20

the technique for measuring the amount of heat involved in a chemical or physical process

Solution calorimeter: measures heat transfer involving rxns in solution or objects or physical changes immersed in water. It under constant pressure

A bomb calorimeter (used for combustion reactions) runs at constant volume

Question 21

Heat transfer

Answer 21

0=q(system)=q(surroundings)
or
system=-surroundings

Heat is transferred between systems and surroundings but never actually lost

Question 22

Tempeture

Answer 22

Temperature is a quantitative measure of the average kinetic energy of the particles in an object

Question 23

Internal energy (U)

Answer 23

The total amount of kinetic and potential energy a system possesses

Question 24

First Law of thermodynamics

Answer 24

Energy can be neither created nor destroyed; it is converted from one form to another (law of conservation of energy)

2. The total energy of the universe is constant
3. Change in internal energy (U) is the sum of the energy changes due to transfer of heat and work

Question 25

Expansion work

Answer 25

work needed to change the volume of the system an important case of expansion against a constant external pressure acting on the system it is negative because energy is lost

Question 26

q(heat sighs) w(sighs)

Answer 26

-q= system releases heat to suroundings q= system gains heat from surroundings -w= work done by system on surroundings w=work done by surroundings on system

Question 27

Enthalpy change (Δ H)

Answer 27

the heat transferred at constant pressure by a chemical reaction or process -Δ H= heat is given off Δ H=heat is gained

Question 28

Sublimation

Answer 28

The matter goes straight from a solid to a gas Oppasite is deposition

Question 29

What is the pressure of boiling water

Answer 29

1 atm

Question 30

Enthalpy of fusion

Answer 30

Δ H of fusion is the enthalpy of melting

Question 31

Hess’s Law

Answer 31

if a process can be written as the sum of several stepwise processes, the enthalpy change of the total process equals the sum of the enthalpy changes for all the steps

Question 32

Standard Enthalpy of Combustion

Answer 32

Standard enthalpy of combustion (H°C): Enthalpy change from combustion of 1 mol of a substance with all reactants/products in std state

Question 32

Standard State

Answer 32

A pure substance at its most stable state at 1 atm ✓ Substance in a solution with concentration 1 M ✓ Must specify temp (usually 298 K (25 °C))

Question 33

Standard Enthalpy of Formation

Answer 33

Standard enthalpy of formation (Hf°): enthalpy change for the reaction forming 1 mole of a pure compound from its constituent elements

Question 34

Is Bond formation exothermic or edothermic

Answer 34

exothermic

Question 35

Is Bond breaking exothermic or edothermic

Answer 35

edothermic

Question 36

Lattice energy/enthalpy

Answer 36

the energy required to separate one mole of a solid ionic cmpd into cations & anions in the gas phase Lattice energy can be calculated theoretically by considering all electrostatic interactions in an ionic solid