Name: _____________________
Period: ___
Heating and Cooling
(1) Determine the amount of energy required to melt 45 g of gold (Hfus = 63.7 J/g).
(2) Determine the mass of ethanol (Hvap = 586 J/g) that can boiled with 1250 J of heat energy
(3) Determine the heat of fusion of acetic acid if freezing 15.0 g releases 2.88 kJ of heat energy.
(4) Determine the heat of vapourization of methane if condensing 1.50 kg releases 7.67x105 J of
(5) Determine the amount of heat required to increase the temperature of 25 g of graphite (c = 0.71 J/g ºC) from 150 ºC to
200 ºC.
(6) Determine the mass of lead (c = 0.130 J/g ºC) that can be heated from 100 ºC to 150 ºC with 1200 J of heat energy.
(7) Determine the final temperature if 550 J of heat energy are released from a 200 g block of silver (c = 0.240 J/g ºC) at 80 ºC.
(8) Determine the initial temperature if 1.5 kJ of heat energy increases the temperature of a 30 g sample of aluminum (c = 0.920
J/g ºC) to 1224 ºC.
(9) Determine the specific heat capacity of glass if 20.2 g can be heated from 10 ºC to 20 ºC with 170 J of heat energy.
(10) (a) Determine the amount of heat energy required to heat 14 g of ice from -15 ºC to 0 ºC (c ice = 2.09 J/g ºC).
(b) Determine the amount of heat energy required to melt 14 g of ice (Hfus water = 334 J/g).
(c) Determine the amount of heat energy required to heat 14 g of water from 0 ºC to 100 ºC (c water = 4.18 J/g ºC).
(d) Determine the amount of heat energy required to boil 14 g of water (Hvap water = 2256 J/g).
(e) Determine the amount of heat energy required to heat 14 g of steam from 100 ºC to 120 ºC (c steam = 2.00 J/g ºC).
(f) Determine the total amount of heat energy (in kJ) required to change 14 g of ice at -15 ºC into steam at 120 ºC.
(11) A 68 g sample of gold (c = 0.130 J/g ºC) is heated to 82.5 ºC and then placed in a calorimeter containing 115.0 g of water at
20.4 ºC. Determine the final temperature.
(12) A 46.2 g sample of copper (c = 0.390 J/g ºC) is heated to 95.4 ºC and then placed in a calorimeter containing 75.0 g of water
at 19.6 ºC. Determine the final temperature.
(13) A 1.50 g sample of camphor (C10H16O) is burned in a calorimeter containing 2.00 kg of water. The temperature of the water
in the calorimeter increases from 50.00 ºC to 56.96 ºC. Determine the heat of combustion of camphor in kJ/mol.
(14) A 1.40 g sample of methanol (CH3OH) is burned in a calorimeter filled with 500 g of water. The water in the calorimeter
changes from 20.0 °C to 27.0 °C. Calculate the heat given off by burning of methanol in kJ/mol.
Answers:
(1) 2.97x103 J
(2) 2.13 g
(3) 192 J/g
(4) 511 J/g
(5) 8.9x102 J
(6) 1.8x102 g
(7) 69 ºC
(8) 1170 ºC
(9) 0.842 J/gºC
(10) (a) 4.4x102 J (b) 4.7x103 J (c) 5.9x103 J
(d) 3.2x104 J (e) 5.6x102 J (f) 43 kJ
(11) 21.5 ºC
(12) 23.7 ºC
(13) -5.90x103 kJ/mol
(14) -335 kJ/mol
Name: _____________________
Period: ___
Heats of Reaction
(1) Classify each reaction as endothermic or exothermic and determine ∆H.
____ (a) 2C4H10 (g) + 13O2 (g) → 8CO2 (g) + 10H2O (g) + 5316.8 kJ/mol; ∆H = ______ kJ/mol
____ (b) N2COH4 (aq) + H2O (l) + 28.3 kJ/mol→ 8CO2 (aq) + 2NH3 (aq); ∆H = ______ kJ/mol
____ (c) CaCO3 (s) + 176 kJ/mol → CaO (s) + CO2 (g); ∆H = ___________ kJ/mol
____ (d) 4NH3 (g) + O2 (g) → 2N2H4 (l) + 2H2O (l) + 286 kJ/mol; ∆H = ___________ kJ/mol
(2) Classify each reaction as endothermic or exothermic and rewrite the equation to include ∆H.
____ (a) 4Ag (s) + 2H2S (g) + O2 (g)
→ 2Ag2S (s) + 2H2O (g)
;∆H = -507.0 kJ/mol
____ (b) 2NaHCO3 (s)
→ Na2CO3 (s) + H2O (g) + CO2 (g)
;∆H = +135.6 kJ/mol
____ (c) 2ClF3 (g) + 2NH3 (g)
→ N2 (g) + 6HF (g) + Cl2 (g)
;∆H = -1196.0 kJ/mol
____ (d) 12CO2 (g) + 11H2O (l)
→ C12H22O11 (s) + 12O2 (g)
;∆H = +5640 kJ/mol
(3) Determine the heat of the reaction from the heats of formation
(a) 2CO2 (g) + N2 (g) → 2NO (g) + 2CO (g)
(b) 2CH3OH (l) + 3O2 (g) → 2CO2 (g) + 4H2O (g)
(c) 2Al (s) + Fe2O3 (s) → Al2O3 (s) + Fe (s)
(d) 4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g)
(e) NO (g) + 2HNO3 (l) → H2O (l) + 3NO2 (g)
(4) (a) For the reaction:C5H12 (l) + 8O2 (g) → 5CO2 (g) + 6H2O (l), ∆Hº = -3536 kJ/mol.
Determine the standard heat of formation of C5H12 (l).
(b) For the reaction: 2ClF3 (g) + 2NH3 (g) → N2 (g) + 6HF (g) + Cl2 (g), ∆Hº = -1196 kJ/mol.
Determine the standard heat of formation of ClF3 (s).
(5) Determine the heat of the reaction from bond energies
(a) H2 + F2 → 2HF
Bond
H–H
F–F
H–F
Bond Energy
(kJ/mol)
432
154
565
(b) Cl2 (g) + 2HBr (g) → 2HCl (g) + Br2 (l)
Bond
Cl–Cl
H–Br
H–Cl
Br–Br
Bond Energy
(kJ/mol)
250
363
427
193
(c) 4HBr (g) + O2 (g) → 2H2O (g) + 2Br2 (g)
Bond
H–Br
O=O
H–O
Br–Br
Bond Energy
(kJ/mol)
363
495
467
193
(d) N2H4 (l) + O2 (g) → N2 (g) + 2H2O (l)
Bond
N–N
N–H
O=O
N≡N
H–O
Bond Energy
(kJ/mol)
160
391
495
941
467
(e) CH4 (g) + 2Cl2 (g) + 2F2 (g) → CF2Cl2 (g) + 2HF (g) + 2HCl (g)
Bond
C–H
Cl–Cl
F–F
C–F
C–Cl
H–F
H–Cl
Bond Energy
(kJ/mol)
413
478
154
458
339
565
427
(6) (a) For the reaction: Br2 (l) + Cl2 (g) → 2BrCl (g) ; ∆Hº = 7 kJ/mol.
Determine the bond energy of a bromine-chlorine bond.
Bond
Cl–Cl
Br–Br
Bond Energy
(kJ/mol)
250
193
(b) For the reaction: 2CH4 (g) + 2NH3 (g) + 3O2 (g) → 2HCN (g) + 6H2O (g); ∆Hº = -1077 kJ/mol.
Determine the bond energy of the carbon-nitrogen triple bond in HCN.
Bond
C–H
N–H
O=O
H–O
Bond Energy
(kJ/mol)
413
391
495
467
(7) Determine the heat of the reaction from Hess’ Law
(a) 2F2 (g) + 2H2O (l) → 4HF(g) + O2 (g)
Steps:
H2 (g) + F2 (g) → 2HF (g)
2H2 (g) + O2 (g) → 2H2O (l)
∆Hº = -542.2 kJ/mol
∆Hº = -571.6 kJ/mol
(b) 2CO (g) + O2 (g) → 2CO2 (g)
Steps:
C (s) + O2 (g) → CO2 (g)
2C (s) + O2 (g) → 2CO (g)
∆Hº = -393.5 kJ/mol
∆Hº = -221.0 kJ/mol
(c) 4PCl3 (g) → P4 (s) + 6Cl2 (g)
Steps:
P4 (s) + 10Cl2 (g) → 4PCl5 (g)
PCl5 (g) → PCl3 (g) + Cl2 (g)
∆Hº = -1910.0 kJ/mol
∆Hº = +138.7 kJ/mol
(d) H2S (g) + 2O2 (g) → H2SO4 (l)
Steps:
H2SO4 (l) → SO3 (g) + H2O (g)
H2S (g) + 2O2 (g) → SO3 (g) + H2O (l)
H2O (g) → H2O (l)
∆Hº = +176 kJ/mol
∆Hº = +661 kJ/mol
∆Hº = -44 kJ/mol
(e) 2C8H18 (l) + 25O2 (g) → 16CO2 (g) + 18H2O (g)
Steps:
8C (s) + 9H2 (g) → C8H18 (l)
C (s) + O2 (g) → CO2 (g)
2H2 (g) + O2 (g) → 2H2O (g)
∆Hº = -250.0 kJ/mol
∆Hº = -393.5 kJ/mol
∆Hº = -571.6 kJ/mol
(f) 5C (s) + 6H2 (g) → C5H12 (g)
Steps:
C (s) + O2 (g) → CO2 (g)
∆Hº = -393.5 kJ/mol
∆Hº = -571.6 kJ/mol
2H2 (g) + O2 (g) → 2H2O (l)
C5H12 (g) + 8O2 (g) → 5CO2 (g) + 6H2O (l) ∆Hº = -3536.6 kJ/mol
Answers:
(1) (a) exo; ∆H = -5316.8 kJ/mol (b) endo; ∆H = 28.3 kJ/mol (c) endo; ∆H = 176 kJ/mol (d) exo; ∆H = -286 kJ/mol
(2) (a) exo; 4Ag (s) + 2H2S (g) + O2 (g) → 2Ag2S (s) + 2H2O (g) + 507.0 kJ/mol
(b) endo; 2NaHCO3 (s) + 135.6 kJ/mol → Na2CO3 (s) + H2O (g) + CO2 (g)
(c) exo; 2ClF3 (g) + 2NH3 (g) → N2 (g) + 6HF (g) + Cl2 (g) + 1196.0 kJ/mol
(d) endo; 12CO2 (g) + 11H2O (l) + 5640 kJ/mol → C12H22O11 (s) + 12O2 (g)
(3) (a) 746 kJ/mol (b) -1277 kJ/mol (c) -850 kJ/mol (d) -908 kJ/mol (e) 74 kJ/mol
(4) (a) -147.5 kJ/mol (b) -169 kJ/mol
(5) (a) -544 kJ/mol (b) -71 kJ/mol (d) -307 kJ/mol (d) -590 kJ/mol (e) -662 kJ/mol
(6) (a) 218 kJ/mol (b) 891 kJ/mol
(7) (a) -512.8 kJ/mol (b) -566 kJ/mol (c) 1355.2 kJ/mol (d)529 kJ/mol (e) -10940.4 kJ/mol (f) -145.7 kJ/mol
Name: _____________________
Period: ___
Entropy and Free Energy
(1) Determine the standard entropy change of the reaction.
(a) SO3 (g) + H2O (l) → H2SO4 (l)
(b) N2H4 (l) + 3O2 (g) → 2NO2 (g) + 2H2O (l)
(c) 2ZnO (s) + 2SO2 (g) → 2Zn (s) + 3O2 (g)
(d) Al2O3 (s) + 3H2 (g) → 2Al (s) + 2H2O (l)
(e) 4NO2 (g) + 6H2O (l) → 4NH3 (g) + 7O2 (g)
(2) (a) For the reaction: CS2 (g) + 3O2 (g) → CO2 (g) + 2SO2 (g), ∆Sº = -143 J/mol K.
Determine the standard entropy of CS2 (g).
(b) For the reaction: 2Al (s) + 3Br2 (l) → 2AlBr3 (s), ∆Sº = -144 J/mol K.
Determine the standard entropy of AlBr3 (s).
(3) Determine the standard free energy change of the reaction.
(a) MgCO3 (s) → MgO (s) + CO2 (g)
(b) 3NO (g) → N2O (g) + NO2 (g)
(c) 2KClO3 (s) → 2KCl (s) + 3O2 (g)
(d) 2NiS (s) + 3O2 (g) → 2SO2 (g) + 2NiO (s)
(e) C6H12O6 (s) + 6O2 (g) → 6CO2 (g) + 6H2O (l)
(4) (a) For the reaction: SF4 (g) + F2 (g) → SF6 (g), ∆Gº = -274 kJ/mol.
Determine the standard free energy of SF4 (g).
(b) For the reaction: 2Al(OH)3 (s) → Al2O3 (s) + 2H2O (g), ∆Gº = 7 kJ/mol.
Determine the standard free energy of Al(OH)3 (s).
(5) Calculate ∆Hº, ∆Sº, and ∆Gº for each reaction at 298 K. State if the reaction is spontaneous or non-spontaneous under
standard conditions.
(a) C2H6 (g) → C2H4 (g) + H2 (g)
(b) C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (l)
(c) 5N2O4 (l) + 4N2H3CH3 (l) → 12H2O (g) + 9N2 (g) + 4CO2 (g)
(d) 3Al (s) + 3NH4ClO4 (s) → Al2O3 + AlCl3 (s) + 3NO (g) + 6H2O (g)
(6) Determine the free energy of the reaction from the steps given.
(a) 2NO2 (g) → N2O4 (g)
Steps:
N2 (g) + O2 (g) → 2NO2 (g)
N2 (g) + O2 (g) → N2O4 (g)
∆Gº = 104 kJ/mol
∆Gº = 98 kJ/mol
(b) 2N2 (g) + 6H2O (g) → 3O2 (g) + 4NH3 (g)
Steps:
2NH3 (g) → N2 (g) + 3H2 (g)
2H2 (g) + O2 (g) → 2H2O (g)
∆Gº = 34 kJ/mol
∆Gº = -458 kJ/mol
(c) 12NH3 (g) + 21O2 (g) → 8HNO3 (g) + 4NO (g) + 14H2O (g)
Steps:
4NH3 (g) + 5O2 (g) → 4NO (g) + 6H2O (g)
2NO (g) + O2 (g) → 2NO2 (g)
3NO2 (g) + H2O (g) → 2HNO3 (g) + NO (g)
∆Gº = -958 kJ/mol
∆Gº = -70 kJ/mol
∆Gº = 13 kJ/mol
(7) (a) Calculate ∆Hº, ∆Sº, and ∆Gº for the following reaction at 298 K:
CaCO3 (s) + H2SO4 (l) → CaSO4 (s) + H2O (g) + CO2 (g)
Substance
CaCO3 (s)
H2SO4 (l)
CaSO4 (s)
H2O (g)
CO2 (g)
∆Hºf (kJ/mol)
-1207
-814
-1433
-242
-393.5
∆Sº (J/mol K)
93
157
107
189
214
(b) Calculate ∆G for the reaction at 200 K. (Assume that enthalpy and entropy do not change with temperature)
(8) (a) Calculate ∆Hº, ∆Sº, and ∆Gº for the following reaction at 298 K:
CH3COOH (g) + NH3 (g) → CH3NH2 (g) + CO2 (g) + H2 (g)
Substance
CH3COOH (g)
NH3 (g)
CH3NH2 (g)
CO2 (g)
H2 (g)
∆Hºf (kJ/mol)
-432.3
-46
-23
-393.5
0
∆Sº (J/molK)
282
193
243
214
131
(b) Calculate ∆G for the reaction at 800 K. (Assume that enthalpy and entropy do not change with temperature)
(9) Determine the standard free energy for the reaction and calculate the equilibrium constant at 298 K.
U CH3OH (g)
(a) CO (g) + 2H2 (g)
(b) 2C (s) + O2 (g)
(c) N2O4 (g)
U 2CO (g)
U 2NO2 (g)
(d) 2SO2 (g) + O2 (g)
(e) N2 (g) + 3H2 (g)
U 2SO3 (g)
U 2NH3 (g)
(10) Determine ∆G for the following equilibrium at 298 K if [SO2] = 1.00 M, [O2] = 0.500 M, and [SO3] =2.00 M
2SO2 (g) + O2 (g)
U 2SO3 (g)
(11) Determine ∆G for the following equilibrium at 800 K if [CH4] = 0.10 M, [C2H2] = 0.40 M, and [H2] = 0.20 M
2CH4 (g)
U C2H2 (g) + 3H2 (g)
Answers:
(1) (a) -170 J/mol K (b) -116 J/mol K (c) 115 J/mol K (d) -248 J/mol K (e) 827 J/mol K
(2) (a) 238 J/mol K (b) 184 J/mol K
(3) (a) 66 kJ/mol (b) -105 kJ/mol (c) -236 kJ/mol (d) -846 kJ/mol (e) -2875 kJ/mol
(4) (a) -831 kJ/mol (b) -1023.5 kJ/mol
(5) (a) ∆Hº = 136.7 kJ/mol ∆Sº = 120.5 J/mol K ∆Gº = 100.8 kJ/mol non spontaneous
(b) ∆Hº = -2220.5 kJ/mol ∆Sº = -373 J/mol K ∆Gº = -2109.3 kJ/mol spontaneous
(c) ∆Hº = -4594 kJ/mol ∆Sº = 3143 J/mol K ∆Gº = -5530.6 kJ/mol spontaneous
(d) ∆Hº =-2677 kJ/mol ∆Sº = 1287 J/mol K ∆Gº = -3060.5 kJ/mol spontaneous
(6) (a) -6 kJ/mol (b) 1306 kJ/mol (c) -3242 kJ/mol
(7) (a) ∆Hº = -47.5 kJ/mol ∆Sº = 260 J/mol K ∆Gº = -125.0 kJ/mol (b) -99.5 kJ/mol
(8) (a) ∆Hº = 61.8 kJ/mol ∆Sº = 113 J/mol K ∆Gº = 28.1 kJ/mol (b) -28.6 kJ/mol
(9) (a) ∆Gº = -26 kJ/mol K = 3.6x104 (b) ∆Gº = -274 kJ/mol K = 1.07x1048 (c) ∆Gº = 6 kJ/mol K = 8.9x10-2
(d) ∆Gº = -142 kJ/mol K = 7.78x1024 (e) ∆Gº = -34 kJ/mol K = 9.1x105
(10) -137 kJ/mol
(11) 307 kJ/mol
Name: _____________________
Period: ___
Free Energy and Electrochemistry
(1) Balance each redox reaction and calculate the overall voltage and standard free energy.
(a) Zn + Pb2+ → Zn2+ + Pb
(d) Cr + Fe2+ → Cr3+ + Fe
(b) Al + Ag+ → Al3+ + Ag
(e) F2 + Li → F- + Li+
(c) Sn + Au3+ → Sn2+ + Au
(f) Cl2 + Fe2+ → Cl- + Fe3+
(2) Determine the overall reaction for each electrochemical cell and calculate the standard cell potential and standard free energy.
(a)
(b)
(c)
(d)
(3) Consider the following electrochemical cell: Cd (s) | Cd2+ (aq) || Cu2+ (aq) | Cu (s)
(a) Write the overall reaction.
(b) Determine the standard cell voltage and standard free energy.
(c) Determine the cell voltage (at 298 K) if [Cd 2+] = 1.25 M and [Cu2+] = 0.75 M
(4) Consider the following electrochemical cell: Pb (s) | Pb2+ (aq) || Ag+ (aq) | Ag (s)
(a) Write the overall reaction.
(b) Determine the standard cell voltage and standard free energy.
(c) Determine the cell voltage (at 298 K) if [Pb2+] = 1.20 M and [Ag+] = 0.60 M
(5) Consider the following electrochemical cell: Sn (s) | Sn2+ (aq) || Cu2+ (aq) | Cu (s)
(a) Write the overall reaction.
(b) Determine the standard cell voltage and standard free energy.
(c) The cell continues to operate until [Sn2+] = 1.40 M. Determine [Cu2+] and the cell voltage at 298 K (note: all solutions
have an initial concentration of 1.0 M).
(6) Consider the following electrochemical cell: Zn (s) | Zn2+ (aq) || Ag+ (aq) | Ag (s)
(a) Write the overall reaction.
(b) Determine the standard cell voltage and standard free energy.
(c) The cell continues to operate until [Zn2+] = 1.16 M. Determine [Ag+] and the cell voltage at 298 K (note: all solutions
have an initial concentration of 1.0 M).
(7) Consider the following electrochemical cell: Al (s) | Al 3+ (aq) || Ni2+ (aq) | Ni (s)
(a) Write the overall reaction.
(b) Determine the standard cell voltage and standard free energy.
(c) The cell continues to operate until [Al3+] = 1.48 M. Determine [Ni2+] and the cell voltage at 298 K (note: all solutions
have an initial concentration of 1.0 M).
(8) Determine the overall reaction for each electrolytic cell and calculate standard free energy.
(a)
(b)
(c)
Answers:
(b) Al + 3Ag+ → Al3+ + 3Ag Eº = 2.46 V ∆Gº = -7.12x105 J
(1) (a) Zn + Pb2+ → Zn2+ + Pb Eº = 0.63 V ∆Gº = -1.2x105 J
(c) 3Sn + 2Au3+ → 3Sn2+ + 2Au Eº = 1.64 V ∆Gº = -9.5x105 J (d) 2Cr + 3Fe2+ → 2Cr3+ + 3Fe Eº = 0.30 V ∆Gº = -1.7x105 J
(f) Cl2 + 2Fe2+ → 2Cl- + 2Fe3+ Eº = 0.59 V ∆Gº = -1.1x105 J
(e) F2 + 2Li → 2F- + 2Li+ Eº = 5.92 V ∆Gº = -1.14x106 J
(2) (a) Mg + Cu2+ → Mg2+ + Cu Eº = 2.71 V ∆Gº = -5.23x105 J
(b) 3Zn2+ + 2Al → 3Zn + 2Al3+ Eº = 0.90 V ∆Gº = -5.2x105 J
2+
2+
3+
4
(c) 3Ni + 2Cr → 3Ni + 2Cr Eº = 0.16 V ∆Gº = -3.1x10 J (d) Br2 + Sn → 2Br- + Sn2+ Eº = 1.21 V ∆Gº = -2.34x105 J
(3) (a) Cd + Cu2+ → Cd2+ + Cu
(4) (a) Pb + 2Ag+ → Pb2+ + 2Ag
(5) (a) Sn + Cu2+ → Sn2+ + Cu
(6) (a) Zn + 2Ag+ → Zn2+ + 2Ag
(7) (a) 2Al + 3Ni2+ → 2Al3+ + 3Ni
(b) Eº = 0.74 V ∆Gº = -1.4x105 J
(b) Eº = 0.93 V ∆Gº = -1.8x105 J
(b) Eº = 0.48 V ∆Gº = -9.3x104 J
(b) Eº = 1.56 V ∆Gº = -3.01x105 J
(b) Eº = 1.41 V ∆Gº = -8.16x105 J
(8) (a) 2Na+ + 2Br- → 2Na + Br2 ∆Gº = 7.3x105 J
(b) Pb2+ + 2Br- → Pb + Br2 ∆Gº = 2.3x105 J
(c) Zn + H2O → Zn2+ + H2 + 2OH- ∆Gº = 1.4x104 J
(c) 0.73 V
(c) 0.91 V
(c) [Cu2+] = 0.60 M Ecell = 0.47 V
(c) [Ag+] = 0.68 M Ecell = 1.55 V
(c) [Ni2+] = 0.28 M Ecell = 1.39 V