Chapter 5

Question 1

Energy

Answer 1

Capacity to do work (w) or transfer heat (q)

Question 2

Kinetic energy (Ek)

Answer 2

Energy due to particle motion and temperature of sample

Question 3

Potential energy (Ep or Eel)

Answer 3

Energy due to particles’ position

Question 4

Kinetic energy equation

Answer 4

KE = (1/2)mv^2

Question 5

Potential energy equation

Answer 5

Eel = (kQ1Q2)/d

Question 6

Thermodynamics

Answer 6

The study of energy and its transformations

Question 7

Thermochemistry

Answer 7

The study of chemical reactions and the energy changes that involve heat

Question 8

Heat (q)

Answer 8

Energy transfer that results from temperature difference

Question 9

Work (w) (Physics)

Answer 9

A force applied across a distance

Question 10

Work (w) (physics) equation

Answer 10

W = F • d

Question 11

Work (w) (chemistry)

Answer 11

A force done by an expanding gas at a constant pressure

Question 12

Work (w) (chemistry) equation

Answer 12

W = -P(delta V)

Question 13

Change in volume equation

Answer 13

Delta V = Vf - Vi

Question 14

Internal energy (E)

Answer 14

Kinetic + potential energy in a sample

Question 15

Change in energy equation

Answer 15

Delta E = Ef - Ei
Delta E = q + w

Question 16

Unit of energy

Answer 16

Joule (J)

Question 17

System

Answer 17

Portion of the universe we study. To chemists, it is typically the chemical reaction.

Question 18

Surroundings

Answer 18

The rest of the universe except the system under study

Question 19

1st law of thermodynamics

Answer 19

Change in universe = 0, so -system = surroundings

Question 20

Closed system

Answer 20

Energy, but not matter, can be transferred between system and surroundings

Question 21

Open system

Answer 21

Energy and matter can be transferred between system and surroundings

Question 22

Isolated system

Answer 22

Energy and matter cannot be transferred between system and surroundings

Question 23

Potential energy is lowest when…

Answer 23

The particles of matter are attracted and close together, where a negative PE is positive and the most stable

Question 24

When PE = 0

Answer 24

Particles are neither repelled nor attracted. There is no interaction.

Question 25

Breaking a chemical bond…

Answer 25

Always requires energy

Question 26

Forming a chemical bond always…

Answer 26

Releases energy

Question 27

If delta E is positive (Ef > Ei)…

Answer 27

Esys has gained energy from Esurr

Question 28

If delta E is negative (Ef < Ei)…

Answer 28

Esys has given energy to Esurr

Question 29

Endothermic reaction

Answer 29

System gains heat (q is positive)

Question 30

Exothermic reaction

Answer 30

System loses heat (q is negative)

Question 31

Work of the system is positive when…

Answer 31

Surroundings work on system (volume decreases)

Question 32

Work of system is negative when…

Answer 32

System works on surroundings (volume increases)

Question 33

q (subscript p)

Answer 33

The heat gained or lost under these conditions of constant pressure

Question 34

q (subscript p) in relation to enthalpy equation

Answer 34

Delta H = q (subscript p)

Question 35

Enthalpy is a _________ property

Answer 35

Extensive; if you double the amount of matter, the delta H is doubled

Question 36

Reversing a reaction…

Answer 36

Changes the sign (+ or -) of delta H

Question 37

The state (s, l, g) of reactants & products are _________

Answer 37

Important; will change overall change in enthalpy of a reaction

Question 38

Because delta H is a state function, the total enthalpy change for a chemical reaction depends only on…

Answer 38

The initial state of the reactants and the final state of the products

Question 39

Calorimetry

Answer 39

Experiment to measure heat transferred between system and surroundings (closed system)

Question 40

Heat capacity (C)

Answer 40

The amount of heat required to raise an object’s temperature by 1K

Question 41

Heat capacity equation

Answer 41

C = q/delta T C = Cs • m

Question 42

Specific heat (Cs)

Answer 42

The amount of heat required to raise 1 gram of object’s temperature by 1K

Question 43

Specific heat equation

Answer 43

Cs = q/(m•delta T)

Question 44

A large value for specific heat means…

Answer 44

More heat required to raise temperature and temperature of substance is not easily changed

Question 45

3 equations for the signs of q

Answer 45

-q lost = q gained -q sys = q surr -q rxn = q solution

Question 46

If the thermometer records a temperature increase…

Answer 46

Heat went into the surroundings, heat left the system (reaction), process is exothermic, and q rxn = delta H rxn = negative

Question 47

If the thermometer records a temperature decrease…

Answer 47

Heat left the surroundings, heat went into the system, process is endothermic, and the q rxn = delta H rxn = positive

Question 48

Delta T equation

Answer 48

Delta T = Tf - Ti

Question 49

Change in enthalpy of a reaction equation

Answer 49

Delta H rxn = q rxn/moles

Question 50

Two types of calorimeters

Answer 50

Coffee cup: reactions at constant pressure and bomb: reactions involving gases

Question 51

Equation for calculating q for a bomb calorimetry

Answer 51

q rxn = -q cal = -C cal • delta T

Question 52

Standard enthalpy of formation (delta H°f)

Answer 52

Enthalpy change for formation of 1 mol of a substance from its elements in their most stable form with all reactants and products at 1 atm pressure and 298 K

Question 53

Bond enthalpy

Answer 53

The energy it takes to break a typical bond (+ energy)