Drill: Calculate the
volume of gas released
o
at 227 C under 83.1 kPa
pressure when 320 kg of
NH4NO3 is exploded
forming N2, O2, & H2O:
Drill: Draw LDDs for:
SCl2
C5H8
-1
HSO4
CHM II HW
• Complete the Take-Home
Test attached to Poly’s
website. The test is due
Monday morning before 1st
period. Pass by my room &
turn it in when arrive.
CHM II HW
• If you arrive late, bring
the test by my room &
show your late pass to
receive full credit. Tests
that are turned late will
lose 20 pts.
Thermochemistry
Chm II
PP-16
Thermochemistry
•The study of heat
transfer in
chemical reactions
Thermochemical
Terms
Heat (H)
•A form of energy
that can flow
between samples of
matter
Heat cannot be
measured directly;
thus, we measure
heat change (DH)
Enthalpy Change
•Heat that can flow
in/out of a system
DH
System
•That part of nature
upon which attention
is focused
Surroundings
•That part of nature
which we are not
focused
Reaction Coordinate
•A graph of energy
change versus time in
a chemical reaction
P
R
Time
Exothermic Rxn
•Chemical reactions
that release, give
off heat, or lose
heat
Exothermic Rxn
•Products will
contain less heat
than the reactants
DH < 0
Endothermic Rxn
•Chemical reactions
that absorb, take in
heat, or gain heat
Endothermic Rxn
•Products will
contain more heat
than the reactants
DH > 0
Thermochemistry
Topics
• Heat Change
• Calorimetry
• Thermochemical
Equation
Topic:
Heat
Change
Specific Heat
•The heat required to
raise one gram of a
o
substance 1 C
o
•c: (J/g C, J/kgK)
Specific Heat
Formula
DH = mcDT
Heat of Fusion
•The heat required to melt
one gram of a substance
at its normal MP
•Hf: (J/g or J/kg)
Heat of Fusion
Formula
DH = mHf
Heat of Vaporization
•The heat required to boil
one gram of a substance
at its normal BP
•Hv: (J/g or J/kg)
Heat of Vap.
Formula
DH = mHv
Calculate the heat change when
10.0 g H2O goes from –100.0oC
o
to 200 C.
MP = 0oC
BP = 100oC
Hf = 334 J/g
HV = 2260 J/g
cice = 2.06 J/gK
cwater = 4.18 J/gK
csteam = 2.02 J/gK
Calculate the heat change when
5.00 g H2O goes from –10.0oC to
o
120 C.
MP = 0oC
BP = 100oC
Hf = 334 J/g
HV = 2260 J/g
cice = 2.06 J/gK
cwater = 4.18 J/gK
csteam = 2.02 J/gK
Drill:
Calculate the heat
required to change 25 g of H2O
from 140.0oC to 60.0oC
o
0C
MP =
csteam= 2.02 J/gK
o
BP = 100 C cwater= 4.18 J/gK
Hf = 334 J/g cice= 2.06 J/gK
HV= 2260 J/g
Review Drill
& Collect
Tests
CHM II HW
• Review PP-16.
• Complete the attached
assignment & turn it in
tomorrow.
Topic:
Calorimetry
Calorimetry
•A study of how to
measure
experimental heat
transfer in a system
Calorimeter
•Device used to measure
heat transfer
•A calorimeter is an
adiabatic system
•Experimental yield
Adiabatic System
•A system that
exchanges zero heat
with its surroundings
DHsystem = 0
DH (J or kJ)
DH = q = the heat or
enthalpy change in a
system
DHsys = SDHsys parts
Calorimetry
DHsystem = 0
DHsys = DHcal + DHrxn
DHrxn = -DHcal (all parts)
DHrxn = -mcDTcal (all)
When Q reacts in a 1.5 kg
calorimeter containing 2.5 kg
water the temp changes from
o
o
22.50 C to 26.50 C.
Calculate DHrxn.
Cwater = 4.18 J/gK
Ccal = 2.00 J/gK
In expensive calorimeters,
the mass is constant; thus,
the mc can be calculated
o
together as C (J/ C).
DHrxn = -mcDTcal
DHrxn = -CDTcal
When X reacts in a 2.0 kg
calorimeter containing 1.5
kg water, the temp changes
o
o
from 22.5 C to 30.5 C.
Calculate DHrxn.
Cwater = 4.18 J/gK
Ccal = 1.50 J/gK
When Z reacts in a 1.0 kg
calorimeter containing 2.0
o
kg water, DT = 30.5 C to
o
20.5 C. Calculate DHrxn.
Cwater = 4.18 J/gK
Ccal = 2.00 J/gK
When X reacts in a 2.0 kg
calorimeter containing 2.0 kg
o
water, DT = 20.0 C to
o
0.0 C. Calculate DHrxn.
50.0 % freezes.
Cice = 2.06 J/gK
Cwater = 4.18 J/gK
Ccal = 2.00 J/gK
Drill: When 40.0 g
NH4NO3 dissolves in
o
460.0 g water at 25.0 C,
o
the temp. falls to 22.5. C.
o
Calculate the DH soln for
NH4NO3. csoln = 4.00 J/gK
Check Drill
&
Check HW
CHM II HW
• Review PP-16
• Complete the attached
worksheet & turn it in
tomorrow (Thermo-1)
Topic:
Thermochemical
Equation (TCE)
Thermochemical
Equation
Terms
Heat of Reaction
•The heat or enthalpy
change of a chemical
reaction
DHrxn
Typical Reaction
•HCl + NaOH 
NaCl + HOH
Heat of Solution
•The heat or enthalpy
change when a
substance is dissolved
DHsoln
Typical
Ionization
KCl 
+
K (aq) + Cl (aq)
Heat of Combustion
•The heat or enthalpy
change when a
substance is burned
DHcombustion
Combustion
Reaction
•CxHy + O2 
CO2 + HOH
Heat of Formation
•The heat required to form
one mole of a compound
from pure elements
DHf
o (kJ/mole)
Rxn Making
Cpds from ele
H2 + ½ O2  H2O
The Degree Symbol
•Indicates standard
conditions & molar
quantities by itself or
from a balanced
equation.
Gibb’s Free Energy
•Energy of a system that
can be converted to work
•Determines spontaneity
DG
Exergonic Reaction
•A reaction in which free
energy is given off
DG < 0
Endergonic Reaction
•A reaction in which
free energy is absorbed
DG > 0
Exergonic Reaction
•A reaction which can be
spontaneous
DG < 0
Endergonic Reaction
•A reaction which
cannot be spontaneous
DG > 0
Reaction at
Equilibrium
DG = 0
Interrelation Term (DG)
DG interrelates
thermochemistry,
chemical equilibria,
& electrochemistry
Energy of Formation
•The energy required to
form one mole of a
compound from pure
elements
o
DGf (kJ/mole)
Entropy
•A measure of
disorder
DS (J/K)
Entropy of Formation
•The entropy of one
mole of a substance
•Sf
o
•Sf (kJ/moleK)
o (J/moleK)
Drill: Identify
type of rxn when:
DG > 0
DG < 0
DG = 0
Thermochemical
Equation
•An equation that
shows changes in
heat, energy, etc
Thermochemical Equation
DH rxn =
SDHf products SDHf reactants
o
o
o
Thermochemical Equation
DG rxn =
SDGf products SDGf reactants
o
o
o
Thermochemical Equation
DS rxn =
SSf products
- SSf reactants
o
o
o
Thermochemical Equation
•Stoichiometry of heat
change
•Solves theoretical yield
Thermochemical Equation
•The
&
steps in
stoichiometry involve
molar conversions
•Use the TCE for this
nd
2
th
4
In stoichoimetric
calculations, the TCE
is used for molar
conversions from
mole to heat or heat to
moles
Interrelating
Equation
DG = DH - TDS
Drill: Define:
• Heat of reaction
• Heat of solution
• Heat of formation
• Energy of formation
• Entropy
Review Drill
&
Check HW
CHM II HW
•Review PP-16
•Complete the attached
worksheet & turn it in
tomorrow (Thermo-1)
Thermochemical Equation
DX rxn =
SDXf products SDXf reactants
o
o
o
Interrelating
Equation
DG = DH - TDS
Calc. DH, DG, & DS when 13.6
g of CaSO4 is changed
o
into CaO + SO2 + O2 at 25 C
Cmpd CaSO4 SO2 CaO
o
DHf -1434.1 -296.8 -635.1
o
DGf -1321.8 -300.2 -604.0
Calculate DH, DG, & DS when
19.7 kg of BaCO3 is
decomposed into BaO + CO2
Cmpd BaCO3 CO2 . BaO
o
DHf -1216.3 -393.5 -553.5
o
DGf -1137.6 -394.4 -525.1
o
Sf
112.1 213.6 70.4
Drill: Calculate DH rxn &
o
DG rxn for:
A + B2C3
AC2 + B
Compd
B2C3 AC2
o
DHf (kJ/mole) -150 -250
o
DGf (kJ/mole) -175 -225
o
Review Drill
&
Review HW
CHM II HW
• Review PP-16
• Complete the attached
worksheet (Thermo-2) & turn it
in on Monday.
• Thermo Lab: Friday
• Test next week.
o
o
Calculate DH , DG , & DS for
AD2 + BC
AC2 + BD
o
at (-23 C)
Cpd BC AD2 AC2 BD
o
DHf -150 -250 -300 -175
o
DGf -125 -225 -250 -150
o
Sf
75
50
80
?
o
Determine Sf BD
Drill:
o
o
o
Calculate DH , DG , & DS
when P + QR
PR2 + Q
Compd
QR PR2
o
DHf (kJ/mole) -250 -450
o
DGf (kJ/mole) -225 -425
Review Drill
&
Check HW
CHM II HW
•Review PP-16
•Test Tuesday
•Lab Due: Wednesday
CHM II HW
•Review PP-16
•Test Wednesday
•Lab Due: Wednesday
Required Constants
Ccup = 0.50 J/gK
Cwater = 4.18 J/gK
CNaOH = 1.00 J/gK
CThermometer = 2.00 J/gK
Lab Results:
Cup H2O NaOH Thermo
5.0 g 50.0 g 2.0 g
20.0 g
o
o
Ti = 22.0 C
Tf = 30.0 C
+
Cmpd NaOH Na
OH
o
DHf
-426.7 -240.1 -230.0
Determine: theoretical and
experimental heat changes
Calculate the potential DHo, DGo,
o
& DS for the reaction involving
the burning of C3H8
Cpd
C3 H 8
CO2
H2 O
o
DHf -103.8 -393.5 -241.8
o
DGf - 23.5 -394.4 -228.6
Calculate the potential DH, DG,
o
& DS for the reaction & Sf for
O2 when burning 8.8 kg of C3H8
Cpd
C3 H8
CO2
H2 O
o
DHf -103.8 -393.5 -241.8
o
DGf - 23.5 -394.4 -228.6
o
Sf
269.9
213.6
188.7
Calculate DH , DG , DS, &
o
at -23 C when:
A + BC
AC + B
Compd
BC AC
o
DHf (kJ/mole) -150 -250
o
DGf (kJ/mole) -175 -225
o
o
Drill: When 2.00 g NaOH
dissolves in 1.0 L water in
a 2.5 kg calorimeter, the
o
temp. went from 22.5 C to
o
o
26.5 C. Calculate: DH soln
Cwater = 4.18 J/gK
Ccal = 2.00 J/gK
Review Drill
&
Check HW
CHM II HW
•The test on
Thermochemistry will
be attached to Poly’s
website later today.
CHM II HW
•The Take-Home Test
on Thermochemistry
Will Be Due by 8:15
Tomorrow.
CHM II HW
•If you are absent,
email the test to me on
Poly’s website by 8:15
Tomorrow.
CHM II HW
•If your test is not
received by 8:15
tomorrow, you must
make arrangements to
take it at another time.
Test
Review
o
DH ,
o
DG ,
Calculate
& DS at
o
227 C for the production of
ammonia from N2 & H2.
Compd NH3
o
DHf
-46.1
o
DGf -16.5
When 25.0 g CaCO3 is made
from CaO & CO2 in a 500. g
calorimeter (C = 1.50 J/gK)
containing 250.0 g of water
(C = 4.18 J/gK), the water
o
o
changes from 25.0 C to 45.0 C.
Calculate DHrxn/mole of CaCO3
Heat Change
•Calculate the heat change
when the temperature of
1.0 kg H2O is changed
o
from –100.0 C to
o
200.0 C.
Bond Energy
•The energy change
when one mole of
bonds are broken
DH bond
o
Bond Equation
DHbond rxn =
o
-(SDHbond products
o
- SDHbond reactants)
o
Bond Energies (kJ/mole)
C-C
C-H
O-H
C=O
347
414
464
715
O=O
498
Calculate the heat
change when 1.00
mole of C2H6 is
burned.
1st Law Thermodynamics
•Total energy change
= heat + work
DE = q + W
Work
•W = Fd
•P = F/A
•V = Ad
•W = PDV = DnRT
2nd Law Thermodynamics
•Total entropy in a
system always
increases assuming no
energy is added to the
system
Thermodynamic
Rxns are State
Rxns
State Reaction
•Reactions that are
independent of the
path; thus not
dependent on
intermediates
Lab 8:
•Thermochemistry
•HW: P 49
•Page: 236
Drill: Calculate DH , DG ,
o
& DS when:
A + BC
AC2 + B
Compd
BC AC2
o
DHf (kJ/mole) -150 -268
o
DGf (kJ/mole) -275 -220
o
o
Hess’s Law
DHrxn is the same
whether it occurs in a
single step or a series
of steps.
Write TE for the process
2A+B
C+A
D+B
H+K
K+M
C+D
H
2K
M+B
Product
Write TE for the process
2A+B
C+A
D+B
H+K
K+M
C+D
H
2K
M+B
Product
2A+B
C+A
D+B
H+K
K+M
3A+ B
C+D
H
2K
M+B
Product
Product
Write TE for the process
2A+ 2B
C+A
D+B
H+K
C+D
2H
2K
P+B
Write TE for the process
2A+2B
C+A
D+B
2H+2K
C+D
2H
2K
2P+2B
o
DH
Drill: Calculate
for
rxn
the production of CaCO3
from CaO & CO2
o
DHf (kJ/mole)
CaCO3 CaO
CO2
-1206.9 -635.1 -393.5
Calculate the %
yield from the
results of the last
two slides
Bond Equation
DHbond rxn =
o
-(SDHbond products
o
- SDHbond reactants)
o
Bond Energies (kJ/mole)
C-C
C-H
O-H
C=O
347
414
464
715
O=O
685
Calculate the heat
change when 6.0
kg of ethane
(C2H6) is burned
in excess oxygen.
Substance
o
S
DH f
A
-100
B
-150
C
-50
D
-125
o
DH
(kJ/mole)
f
o
S
DH f
H
-150
K
-200
P
-250
Q
-300
Solve
A+B
C+A
D+B
H+K
o
DH
for
TE
rxn
2C+2D
2H+P
2K+P
P+Q
Solve
A+B
2C + 2A
2D + 2B
4H + 4K
o
DH
for
TE
rxn
2C+2D
4 H + 2P
4K + 2P
4P + 4Q
Drill: What does each symbol
represent?
Define what is represents:
DH:
DG:
DS:
Test on
Thermochemistry
Tomorrow
Review
Calculate DHtotal, when 40.0 g of
o
H2O is changed from - 25 C to
o
o
125 C. FPw = 0.0 C
o
BPw = 100.0 C Hv = 2260 J/g
Cice = 2.06 (J/g K) Hf = 334 J/g
Cwater = 4.18 (J/g K)
Csteam = 2.02 (J/g K)
Calculate DH , DG , & DS for
N2O5 + H2O
HNO3
o
Cpd
o
DHf
o
DGf
N2O5
-11.3
-10.4
o
o
H2O
HNO3
-285.8
-237.2
-174.1
-151.5
When 10.8 g N2O5 is added to a
1.50 kg calorimeter (C = 1.00 J/gK)
containing 1.00 kg of H2O
(C = 4.18 J/gK), the N2O5reacts
with the water forming HNO3.
The temp. of the system changes
o
o
from 23.000 C to 23.750 C.
Calculate the DHrxn/mole N2O5.
Calculate the %
yield of the
reaction in the last
two slides.
Solve
X+Y
W+X
2S+P
R+S
o
DH
for TE
2W+2Z
2R+P
Z+Y
P+Q
60 kJ
40 kJ
50 kJ
80 kJ
o
DH
X+Y
2W + 2X
2Z + 2Y
4 R + 4S
3X + 3Y
for TE
2 W + 2 Z 60 kJ
4 R + 2P 80 kJ
4 S + 2P -100 kJ
4P + 4Q 320 kJ
8P + 4Q 360 kJ
Calculate DH , DG , & DS for
PbO2 + CO
CO2 + Pb
o
Cpd
o
DHf
o
DGf
PbO2
-277.4
-217.4
o
CO
-110.5
-137.2
o
CO2
-393.5
-394.4
Calculate: Teq & DH of 48 g PbO2
Test
Tomorrow
When 4.20 g MgCO3 is
decomposed to MgO & CO2 in
a 2500.0 g calorimeter (C =
2.00 J/gK) containing 1.0.kg of
water (C = 4.18 J/gK), the
o
water changes from 23.00 C to
o
13.00 C. Calculate the heat of
rxn/mole of MgCO3
AP Homework:
Read: Chapter 9
Power Point: 17
Chm II Homework:
Read: Chapter 16
Power Point: 19