The Medical College - Page 18
STANDARD ENERGIES OF FORMATION
OF COMPOUNDS AT 1 atm AND 298 K
MODEL MCAT
Some useful reference material can be found
beginning on page 145.
The full-length model MCAT that follows will
provide you with helpful practice. Be
sure to take the model test under strict test
conditions, timing each section as instructed.
First, remove the answer sheets.
After you complete the test, check your answers
with the explanations that begin on
page 193. Then, compute your MCAT scores using
the Conversion Tables and the Self-
Scoring Chart on page 210. Doing this will help
you to determine areas of strength and
weakness. If your computed MCAT score on the
model test is lower than 8 in any of the
three numerically graded subtests, you should
plan additional work in that area. Your
writing samples should be evaluated, if
possible, by an English instructor.
Heat (Enthalpy)
Free Energy
of Formation*
of Formation
Compound
(
Hf )( Gf )
kJ/mol
kcal/mol
kJ/mol
kcal/mol
Aluminum oxide Al2O3(s)
1676.5
400.5
1583.1
378.2
Ammonia NH3(g)
46.0
11.0
16.3
3.9
Barium sulfate BaSO4(s)
1473.9
352.1
1363.0
325.6
Calcium hydroxide Ca(OH)2(s)
986.6
235.7
899.2
214.8
Carbon dioxide CO2(g)
393.9
94.1
394.7
94.3
Carbon monoxide CO(g)
110.5
26.4
137.3
32.8
Copper(II) sulfate CuSO4(s)
771.9
184.4
662.2
158.2
Ethane C2H6(g)
84.6
20.2
33.1
7.9
Ethene (ethylene) C2H4(g)
52.3
12.5
68.2
16.3
Ethyne (acetylene) C2H2(g)
226.9
54.2
209.3
50.0
Hydrogen fluoride HF(g)
271.3
64.8
273.3
65.3
Hydrogen iodide HI(g)
26.4
6.3
1.7
0.4
Iodine chloride ICl(g)
18.0
4.3
5.4
1.3
Lead(II) oxide PbO(s)
215.6
51.5
188.4
45.0
Methane CH4(g)
74.9
17.9
50.7
12.1
Magnesium oxide MgO(s)
601.9
143.8
569.7
136.1
Nitrogen(II) oxide NO(g)
90.4
21.6
86.7
20.7
Nitrogen(IV) oxide NO2(g)
33.1
7.9
51.5
12.3
Potassium chloride KCl(s)
437.0
104.4
409.4
97.8
Sodium chloride NaCl(s)
411.5
98.3
384.3
91.8
Sulfur dioxide SO2(g)
296.8
70.9
300.1
71.7
Water H2O(g)
242.0
57.8
228.6
54.6
Water H2O( )
285.9
68.3
237.3
56.7
*Minus sign indicates an exothermic
reaction.
Sample equations:
2Al(s)
O2(g)
Al2O3(s)
400.5 kcal
2Al(s)
O2(g)
Al2O3(s)
H
400.5 kcal/mol
3
2
3
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