Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry > Chapter 5 - Thermochemistry > Flashcards

Chapter 5 - Thermochemistry Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

define thermochemistry

A

the study of the energy changes that accompany physical or chemical changes in matter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define energy

A

the ability to do work

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

SI units for energy

A

Joules (J)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

define work

A

the amount of energy transferred by a force over a distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

SI units for work

A

Joules (J)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how can energy be classified?

A

as potential energy or kinetic energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

define potential energy

A

the energy of a body of system due to its position or composition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

define kinetic energy

A

the energy of an object due to its motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the energy associated with chemical bonds?

A

potential energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are chemical bonds?

A

attractive forces between the nucleus of one atom or ion and the negative charges of the electrons in the other atom or ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the amount of energy released/absorbed in a chemical reaction equal to?

A

the difference between the potential energy of the bonds in the reactants and the potential energy of the bonds in the products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

define thermal energy

A

the total quantity of kinetic and potential energy in a substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does the quantity of thermal energy in a substance depend on?

A

how fast its entities are moving

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are entities?

A

atoms, molecules, ions, polyatomic ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

when a substance absorbs thermal energy, what happens?

A

its entities move at a greater speed, and the substance warms up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what happens when a substance releases thermal energy to its surroundings?

A

its entities move more slowly, and the substance cools

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define heat

A

a verb that refers to the transfer of thermal energy from a warm object to a cooler object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

define temperature

A

a measure of the average kinetic energy of entities in a substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

which has a higher temperature and why: iceberg vs hot cup of water

A

the hot cup of water has a higher temperature because the average water molecule in a cup of hot water has a higher temperature than the average water molecule in an iceberg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

which has more thermal energy and why: iceberg vs hot cup of water

A

the iceberg has more thermal energy because the iceberg contains more water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

define law of conservation of energy

A

energy cannot be created or destroyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what can energy only do?

A

be converted from one form to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how do chemists divide the universe?

A

chemical system, its surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

define chemical system

A

a group of reactants and products being studied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

define surroundings

A

all the matter that is not part of the system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what two ways can chemical systems be classified?

A

open, closed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

define open system

A

a system in which both matter and energy are free to enter and leave the system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

define closed system

A

a system in which energy can enter and leave the system, but matter cannot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what happens with the chemical bonds in a chemical reaction?

A

chemical bonds in the reactants are broken, new bonds are formed to produce the products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

potential energy of entities in a stable structure vs potential energy of individual isolated atoms

A

potential energy of entities in a stable structure is lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what does bond breaking and formation require from energy

A

bond breaking requires energy while bond formation releases energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what do entities in a stable structure include?

A

atoms, ions, or molecules in an ionic compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

define exothermic

A

releasing energy to the surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

when is more energy released in an exothermic reaction?

A

more energy is released from the formation of new bonds of products than is required to break the bonds in the reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

potential energy and bonds of products vs reactants in exothermic reaction?

A

products have lower potential energy and stronger bonds than reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what happens when an exothermic reaction releases energy?

A

the temperature of the surroundings increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

define endothermic

A

absorbing energy from the surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what occurs in an endothermic reaction with the chemical system?

A

absorbs energy from its surroundings and increases its potential energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

potential energy and bonds of products vs reactants in endothermic reaction

A

products have higher potential energy and weaker bonds than the reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what type of reaction can a chemical reaction take?

A

endothermic or exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what type of reaction can a nuclear reaction take?

A

exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

name two nuclear reactions involving large quantities of energy

A

fusion and fission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

define fusion

A

the process of combining two or more nuclei of low atomic mass to form a heavier, more stable nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

define fission

A

the process of using a neutron to split a nucleus of high atomic mass into two nuclei with smaller masses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what types of changes can a potential energy change result from?

A

any physical, chemical, or nuclear change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

magnitudes of potential energy changes from lowest to highest

A

phase change, chemical change, nuclear change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what is the symbol for specific heat capacity?

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

define specific heat capacity

A

the quantity of thermal energy required to raise the temperature of 1 g of a substance by 1 ℃

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

SI units for specific heat capacity

A

J/(g・℃)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what is the specific heat capacity of liquid water?

A

4.18 J/(g・℃)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

specific heat capacity of water vs sand and what this causes

A

specific heat capacity of water is higher than sand so it takes less to raise the temperature of sand and it will become hotter than the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

define calorimetry

A

the experimental process of measuring the thermal energy change in a chemical or physical change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

define calorimeter

A

a device that is used to measure thermal energy changes in a chemical or physical change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what does a calorimeter consist of?

A

a well insulated reaction chamber, a tight fitting cover with insulated holes for a thermometer, and some mechanism to stir the contents of the calorimeter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what does using an insulated chamber minimize?

A

energy loss to the surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

what is a coffee cup calorimeter composed of?

A

polystyrene cover and two cups, inner cup holds chemical system and a liquid, usually water, outer cup provides additional insulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

how are changes in the thermal energy of the chemical system detected in a coffee cup calorimeter?

A

through temperature changes in the water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

2 assumptions of insignificance made when using a coffee cup calorimeter

A

any thermal energy transferred from the calorimeter to the outside environment is negligible, any thermal energy absorbed by the calorimeter itself is negligible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

assumption of calculations made when using a coffee cup calorimeter

A

all dilute, aqueous solutions have the same density and specific heat capacity as water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

density of water

A

1.00 g/mL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

when are these assumptions valid?

A

for chemical or physical changes that take place in water or a dilute, aqueous solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

what is q

A

the total amount of thermal energy released or absorbed by a chemical system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what does the magnitude of q depend on?

A

the mass of the substance, the specific heat capacity of the substance, the temperature change experienced by the substance as it warms or cools

64
Q

formula to calculate q

A

q = mcΔT

65
Q

what does the symbol m stand for

A

mass of the substance

66
Q

formula to calculate ΔT

A

ΔT = Tfinal - Tinitial

67
Q

what happens when q has a negative value to thermal energy, reaction change, and water

A

system transfers thermal energy to the surroundings, reaction change is exothermic, temperature of water increases

68
Q

what happens when q has a positive value to thermal energy, reaction change, and water

A

system absorbs thermal energy from its surroundings, reaction change is endothermic, temperature of the water decreases

69
Q

in a coffee cup calorimeter, what is the surroundings?

A

the water

70
Q

what substances contain a certain amount of thermal energy?

A

any substance undergoing a physical or chemical change

71
Q

what is the symbol for enthalpy?

A

H

72
Q

define enthalpy

A

the total amount of thermal energy in a substance

73
Q

how is enthalpy measured?

A

cannot be measured

74
Q

what is the symbol for enthalpy change?

A

ΔH

75
Q

define enthalpy change

A

energy released to or absorbed from the surroundings during a chemical or physical change

76
Q

how is enthalpy change measured?

A

using calorimetry data

77
Q

formula for enthalpy change equal to thermal energy in and out of the system

A

ΔHsystem = |qsystem|

78
Q

what condition needs to be in place to use the formula ΔHsystem = |qsystem|

A

pressure remains constant

79
Q

for a chemical reaction, what is the formula for enthalpy change?

A

ΔH = Hproducts - Hreactants

80
Q

when is the enthalpy change positive, and what kind of reaction is this?

A

products have a greater enthalpy than reactants, endothermic reaction

81
Q

when is the enthalpy change negative and what kind of reaction is this

A

products have a lower enthalpy than reactants, exothermic reaction

82
Q

in an exothermic reaction, explain what happens with the kinetic and potential energy of the chemical system and the surroundings

A

chemical system goes from high potential energy to low potential energy, surroundings goes from low kinetic energy to high kinetic energy

83
Q

what is the symbol for molar enthalpy change?

A

ΔHr

84
Q

define molar enthalpy change

A

the enthalpy change associated with a physical, chemical, or nuclear change involving 1 mol of a substance

85
Q

SI units for molar enthalpy change

A

J/mol

86
Q

what does the subscript r represent in the molar enthalpy change

A

reaction type

87
Q

how to balance equations for thermochemical reaction

A

relevant substance has coefficient of 1, other substances may have fractional coefficients

88
Q

4 types of thermochemical reaction

A

solution, combustion, vaporization, formation, neutralization

89
Q

subscript symbol for solution thermochemical reaction

A

sol

90
Q

subscript symbol for combustion thermochemical reaction

A

c

91
Q

subscript symbol for vaporization thermochemical reaction

A

vap

92
Q

subscript symbol for neutralization thermochemical reaction

A

neut

93
Q

explain solution reaction

A

solid reactant to aqueous products with appropriate charge on products

94
Q

explain combustion reaction

A

gas and oxygen gas forms carbon dioxide gas and liquid water

95
Q

explain vaporization reaction

A

liquid turns to gas

96
Q

explain formation reaction

A

solid reactants unless they are gas forms liquid product

97
Q

explain vaporization reaction

A

aqueous base and acid forms aqueous product and liquid water

98
Q

relevant substance of vaporization reaction

A

per mole of acid or base

99
Q

which reactions don’t have relevant substance in reactant

A

formation

100
Q

what does the enthalpy change depend on

A

quantity of matter than undergoes the change

101
Q

how much more energy is needed to convert 1 L of liquid water to water vapour than 500 mL

A

2 times

102
Q

formula to calculate enthalpy change for substances other than 1 mol

A

ΔH=nΔHr

103
Q

which substances undergo a change in enthalpy

A

all those in chemical reactions

104
Q

what is a chemical equation that describes the enthalpy change of a reaction

A

thermochemical reaction

105
Q

what are the two ways to write a thermochemical reaction

A

adding energy term as product/reactant, writing enthalpy change after balanced equation where ΔH = +/- enthalpy change

106
Q

what is indicated by an energy term added as a product and what type of reaction is this

A

indicates energy released by the chemical system, exothermic reaction

107
Q

what is indicated by an energy term added as a reactant and what type of reaction is this

A

indicate energy absorbed by the chemical system, endothermic reaction

108
Q

2 ways to represent thermochemical enthalpy changes

A

energy terms, potential energy diagrams

109
Q

define potential energy diagram

A

a graphical representation of the energy transferred during a physical or chemical reaction

110
Q

in a chemical reaction, what has potential energy?

A

both products and reactants

111
Q

potential energy symbol for potential energy diagram

A

Ep (KJ)

112
Q

x-axis, y-axis and title of potential energy diagram

A

x-axis: reaction progress, y-axis: potential energy, potential energy symbol, title: potential energy diagram during a(n) __ reaction

113
Q

how do you show change from the arrow of potential energy diagrams

A

use molar enthalpy change symbol = +/- change

114
Q

in a potential energy diagram, what reaction is it when arrow goes down?

A

exothermic

115
Q

in a potential energy diagram, what reaction is it when arrow goes up?

A

endothermic

116
Q

what does the bond energy of a single covalent bond breaking mean?

A

the energy required to break one mol of the covalent bond into 1 mol of one atom and 1 mol of another

117
Q

what does the bond energy mean when a covalent bond forms?

A

the amount of energy released

118
Q

how do we use bond energies

A

can calculate enthalpy change of an chemical reaction f we know the bond energies of the chemical bonds of the reactants and products

119
Q

define bond dissociation energy

A

the energy required to break a given chemical bond

120
Q

why are bond dissociation energies given as average bond energies?

A

the energy depends on the types of atoms and bonds in the same molecule

121
Q

which has larger bond energies: multiple bonds or single bonds

A

multiple bonds

122
Q

what is suggested by multiple bonds having larger bond energies?

A

multiple bonds are stronger

123
Q

what is the relationship between number of bonds between atoms and bond length

A

as the number of bonds increase, the bond length shortens

124
Q

what is meant by number of bonds

A

number of electrons shared

125
Q

what is meant by bond length

A

distance between the nuclei

126
Q

what must happen first in a chemical reaction

A

bonds must break

127
Q

what must happen for bonds to break, what is the reaction type, and what is the sign of the energy term

A

energy must be added, an endothermic process, energy terms are positive

128
Q

what must happen for bonds to form, what is the reaction type, and what is the sign of the energy term?

A

energy is released, an exothermic process, energy terms are negative

129
Q

what is the middle step of the enthalpy change of a reaction using bond energies

A

ΔH = sum of energies required to break old bonds (positive) - sum of energies released in the formation of new bonds (negative)

130
Q

what is the equation for enthalpy change using bond energies

A

ΔH = Σn x D (bonds broken) - Σn x D (bonds formed)

131
Q

what does the symbol D mean and what is the sign?

A

bond energy, always positive

132
Q

what are the units of D

A

KJ/mol

133
Q

why can we use bond energies?

A

because bond energies of similar bonds are nearly the same in different molecules and they provide a good approximation of the actual bond energy value

134
Q

what is the change in enthalpy of a chemical process independent of?

A

the path taken

135
Q

what does the change in enthalpy being independent of the path taken mean?

A

going from an initial set of reactants to a final set of products in one step or a series of steps has the same enthalpy change

136
Q

what happens if you add the thermochemical equations used in a series of steps, including the sum of enthalpy changes?

A

you get the overall, net reaction and the enthalpy change for the net reaction

137
Q

define hess’s law

A

the enthalpy change for the conversion of reactants to products is the same whether the conversion occurs in one step or several steps

138
Q

how is hess’s law useful?

A

useful to study energy changes in chemical reactions that cannot be analyzed using calorimetry

139
Q

what 2 rules must you follow when using Hess’s rule to calculate enthalpy change?

A

if you reverse the chemical reaction, you must also reverse the sign of ΔH. if the coefficients in a balanced equation are multiplied by a factor, the value of ΔH is multiplied by the same factor

140
Q

what is proportional to the magnitude of ΔH

A

the number of moles of reactants and products in a reaction

141
Q

define formation equations

A

represent the formation of a compound from its elements

142
Q

define standard enthalpy of formation

A

the change in enthalpy that accompanies the formation of 1 mol of a compound from its elements in the standard state

143
Q

what is the symbol for standard enthalpy of formation

A

ΔHf°

144
Q

define standard state

A

the most stable form of a substance under stable conditions

145
Q

what is the standard ambient temperature and pressure

A

25 degrees celsius and 100 kPa

146
Q

what is the standard state of most elements

A

solid

147
Q

which elements are gases in their standard state?

A

diatomic elements, and noble gases

148
Q

list the diatomic elements

A

hydrogen, oxygen, nitrogen, fluorine, chlorine

149
Q

which elements are liquids in their standard state?

A

mercury, bromine

150
Q

what is the standard state for a substance in a solution?

A

1 mol/L

151
Q

what does the degree sign for standard enthalpy of formation mean?

A

the process takes place under standard conditions

152
Q

what is the standard enthalpy of formation of an element in its standard state?

A

0

153
Q

why is the standard enthalpy of formation of an element in its standard state 0?

A

an element is in its most fundamental form at standard conditions

154
Q

what must you do to balance the standard enthalpy of formation equation?

A

1 mol of the product

155
Q

type of reaction of enthalpies of formation

A

exothermic or endothermic

156
Q

how do we calculate standard enthalpies of reaction from standard enthalpies of formation formula?

A

ΔHr° = ΣnproductsΔH°products - ΣnreactantsΔH°reactants

Chemistry (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions