thermo-chemistry
DESCRIPTION
Calculate the volume of gas released at 227 o C under 83.1 kPa pressure when 16 kg of NH 4 NO 3 is exploded forming N 2 , O 2 , & H 2 O:. Thermo-chemistry. Thermochemistry. The study of heat transfer in chemical reactions. Thermochemistry. Heat change Calorimetry TCE. - PowerPoint PPT PresentationTRANSCRIPT
Calculate the volume of gas released at 227oC
under 83.1 kPa pressure when 16 kg of NH4NO3 is exploded forming N2,
O2, & H2O:
Thermo-chemistry
Thermochemistry
•The study of heat transfer in
chemical reactions
Thermochemistry•Heat change
•Calorimetry
•TCE
Thermo-chemical
Terms
System
•That part of nature upon which
attention is focused
Surroundings•That part of nature
around the part upon which we are
focused
Reaction Coordinate
•A graph of energy change versus time in a chemical reaction
Time
Ene
rgy
RP
Exothermic Rxn•Chemical reactions
that release, give off heat, or lose
heat
Endothermic Rxn
•Chemical reactions that absorb, take in heat, or gain heat
Heat Change
Specific Heat•The heat required to raise one gram of a substance 1oC
•C: (J/goC, J/kgoK)
Sp. Heat
H = mCT
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
H = 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.
H = mHv
Calculate the heat change when 10.0 g H2O goes from –100.0oC to 200oC.MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g
Cice = 2.06 J/gKCwater = 4.18 J/gK Csteam = 2.02 J/gK
Drill: Calculate the heat required to change 25 g
of water from 140.0oC to 60.0oC
MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g
Cice = 2.06 J/gKCwater = 4.18 J/gK Csteam = 2.02 J/gK
Calorimetry•Experimental measure of heat transfer
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
Hsystem = 0
H (J)H = q = the heat or enthalpy change in a system
Hsys = mCTsys parts
CalorimetryHsystem = 0
Hsys = Hcal + Hrxn
Hrxn = -Hcal
Hrxn = -mCTcal
When Q reacts in a 1.5 kg calorimeter containing 2.5
kg water ch. from 22.5oC to 26.5oC. Calculate Hrxn.
Cwater = 4.18 J/gK Ccal = 2.00 J/gK
When X reacts in a 2.0 kg calorimeter containing 1.5 kg water went from 22.5oC to 30.5oC. Calculate Hrxn.
Cwater = 4.18 J/gK Ccal = 1.50 J/gK
Homework•Problems 7 & 8
•On page 234
Thermo-chemical Equation
Terms
Typical Reaction
•HCl + NaOH NaCl + HOH
Heat of Reaction•The heat or enthalpy change of a chemical reaction
Hrxn
Typical Ionization
HCl
H+(aq) + Cl-
(aq)
Heat of Solution
•The heat or enthalpy change when a substance is dissolved
Hsoln
Combustion Reaction
•CxHy + O2
CO2 + HOH
Heat of Combustion•The heat or enthalpy change when a substance is burned
Hcombustion
Rxn Making Cpds from ele
H2 + ½ O2 H2O
Heat of Formation•The heat required to form one mole of a compound from pure elements
Hfo (kJ/mole)
The Degree Symbol•Indicates standard conditions & molar
quantities by itself or from a balanced
equation.
Enthalpy•Heat flow in a
system
H
Gibb’s Free Energy•Energy of a system that can be converted to work
•Determines spontaneity
G
Energy of Formation•The energy required to form one mole of a compound from pure elements
Gfo (kJ/mole)
Exergonic Reaction•A reaction in which free energy is given off
G < 0
Endergonic Reaction
•A reaction in which free energy is absorbed
G > 0
Exergonic Reaction•A reaction which can be spontaneous
G < 0
Endergonic Reaction
•A reaction which cannot be spontaneous
G > 0
Reaction at Equilibrium
G = 0
Interrelation Term (G)
G interrelates thermochemistry,
chemical equilibria, & electrochemistry
Entropy•A measure of disorder
So
Entropy of Formation•The entropy of one mole of a substance
•Sfo (J/moleoK)
Drill: Define:• Heat of reaction
• Heat of solution
• Heat of formation
• Energy of formation
• Entropy of formation
Thermochemical Equation
•An equation that shows changes in heat, energy, etc
Drill: Identify type of rxn when:
G > 0G < 0G = 0
Thermochemical Equation
Ho
rxn Hf
o
productsHf
o
reactants
Thermochemical Equation
Go
rxn Gf
o
productsGf
o
reactants
Thermochemical Equation
So
rxnSf
o
products
Sfo
reactants
Thermochemical Equation
•Stoichiometry of heat change
•Solves theoretical yield
Interrelating Equation
GH
S
Calculate H, G, & S when 19.7 kg of BaCO3 is decomposed into BaO + CO2
Cmpd BaCO3 CO2 . BaO
Hf
o -1216.3 -393.5 -553.5
Gf
o -1137.6 -394.4 -525.1
Sf
o 112.1 213.6 70.4
Calculate H, G, & S when 13.6 g of CaSO4 is changed
into CaO + SO2 + O2 at 27oC
Cmpd CaSO4 SO2 CaO
Hf
o -1434.1 -296.8 -635.1
Gf
o -1321.8 -300.2 -604.0
Calculate the potential H, G, & S for the reaction & Sf
o for
O2 when burning 8.8 kg of C3H8 Cpd C3H8 CO2 H2O
Hf
o-103.8 -393.5 -241.8
Gf
o- 23.5 -394.4 -228.6
Sf
o269.9 213.6 188.7
Calculate Ho, Go, & S when P + QR PR2 + Qat -23oC & Teq
Compd QR PR2
Hfo(kJ/mole) -250 -450
Gfo(kJ/mole) -225 -425
Heat Change•Calculate the heat change when the temperature of 1.0 kg H2O is changed from –100.0oC to 200.0oC.
Lab Results: Cup H2O NaOH Thermo
5.0 g 50.0 g 4.0 g 15.0 g Ti = 22.0
oC Tf = 27.0
oC
Cmpd NaOH Na+ OH-
Hf
o -425.6 -240.1 -230.0
Determine: theoretical and experimental heat changes
When 2.00 g NaOH dissolves in a 1.0 L water in a 2.5 kg calorimeter, the temp. went
from 22.5oC to 26.5oC. Calculate: Ho
soln Cwater = 4.18 J/gK Ccal = 2.00 J/gK
Bond Energy•The energy change
when one mole of bonds are broken
Ho
bond
Bond Equation
Hbondo
rxnHbond
o
products
Hbondo
reactants
Bond Energies (kJ/mole)
C-C 347
C-H 414
O-H 464
C=O 715
Drill:Calculate H, G, & S in the production of 831mL
ammonia at 227oC under
250.0 kPa pressureCompd NH3
Hfo -46.1
Gfo -16.5
HOLY MACKERAL
1st Law Thermodynamics
•Total energy change = heat + work
E = q + W
Work•W = Fd
•P = F/A
•V = Ad
•W = PV = nRT
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
Calculate Ho, Go, & S when A + BC AC2 + Bat -23oC & solve Teq
Compd BC AC2
Hfo(kJ/mole) -150 -250
Gfo(kJ/mole) -125 -225
Hess’s LawHrxn is the same
whether it occurs in a single step or a series
of steps.
Calculate Ho, Go, & S when A + BC AC + Bat -23oC & Teq
Compd BC ACHf
o(kJ/mole) -150 -250Gf
o(kJ/mole) -175 -225
Write TE for the process2 A + B C + D
C + A H
D + B 2 K
H + K M + B
K + M Product
Write TE for the process2 A + B C + D
C + A H
D + B 2 K
H + K M + B
K + M Product
Write TE for the process2 A + 2 B C + D
C + A 2 H
D + B 2 K
H + K P + B
Write TE for the process2 A + 2 B C + D
C + A 2 H
D + B 2 K
2 H + 2 K 2 P + 2 B
Drill: When 5.00 g NsCO3 is decomposed to NsO & CO2 in a 500.0 g calorimeter (C = 1.50 J/gK) containing 250 g of water (C = 4.18 J/gK), the water changes from 25.00oC to 45.00oC. Calculate the heat of rxn/mole of NsCO3
Substance Hof(kJ.mole)
S H S HA -100 H -150B -150 K -200C -50 P -250D -125 Q -300
Write TE for the process A + B 2 C + 2 D
C + A 2 H + P
D + B 2 K + P
H + K P + Q
Review
Calculate Htotal, when 40.0 g of
H2O is changed from - 25oC to
125oC. FPw = 0.0oC
BPw = 100.0 oC Hv = 2260 J/gCice = 2.06 (J/g K) Hf = 334 J/gCwater = 4.18 (J/g K)Csteam = 2.02 (J/g K)
Calculate Ho, G
o, & S for
AD2 + BC AC2 + BD
at (-23oC)
Cpd BC AD2 AC2 BD
Hf
o -150 -250 -300 -175
Gf
o -125 -225 -250 -150
Sf
o 75 50 80 ?
Determine Sf
o
BD
Calculate Ho, Go, & So for PbO2 + CO CO2 + Pb
Cpd PbO2 CO CO2 Hf
o -277.4 -110.5 -393.5
Gfo -217.4 -137.2 -394.4
Calculate: Teq & H of 48 g PbO2
Calculate Ho, Go, & So for N2O5 + H2O HNO3
Cpd N2O5 H2O HNO3 Hf
o -11.3 -285.8 -174.1
Gfo -10.4 -237.2 -151.5
What does each symbol represent?
Define what is represents:
H:G:S: