Modern Engineering Thermodynamics

Problems 647
c. The percent excess air used in the combustion process.
d. The dew point temperature of the products at atmospheric
pressure.
38. An Orsat analysis of the (dry) products of combustion of an
unknown hydrocarbon indicates that it consists of only 26.1%
CO and 73.9% N 2 , with no CO 2 or O 2 present. Determine
a. The fuel model ðC n H m Þ:
b. The composition of the fuel on a percent mass basis.
c. The percent theoretical air used.
d. The dew point temperature of the combustion products at
atmospheric pressure.
39.* The combustion of a new fuel that is a mixture of a liquid
hydrocarbon and hydrogen gas is to be modeled as a single
hydrocarbon. An Orsat analysis of the dry exhaust products of
this new fuel shows 6.00% CO, 6.00% O 2 , and 88.0% N 2
(no CO 2 is present). Determine
a. The fuel model ðC n H m Þ of this mixture.
b. The percentages by mass of carbon and hydrogen present in
the mixture.
c. The mass air/fuel ratio used in the combustion process.
d. The dew point temperature of the exhaust products at
0.152 MPa.
40.* An unknown hydrocarbon fuel produced an Orsat dry exhaust
gas analysis of 8.30% CO 2 , 0.00% CO, 9.10% O 2 , and 82.6%
N 2 : Determine
a. The fuel model ðC n H m Þ:
b. The composition of the fuel on a percent mass basis.
c. The percent of theoretical air used.
d. The dew point temperature of the exhaust gas when it is at
0.1015 MPa.
41. Amounts of 9.70% CO 2 , 1.10% CO, 0.00% O 2 , and 87.2% N 2
are found in the Orsat analysis of the dry exhaust gas produced
by the cataclysmic combustion of an unknown hydrocarbon
substance in air. Determine
a. The fuel model ðC n H m Þ of the hydrocarbon.
b. The mass percentages of carbon and hydrogen in the fuel.
c. The percent of deficit air used.
d. The molar percentage of water vapor in the exhaust before it
was dried.
42.* The Orsat analysis of the (dry) products of combustion of an
unknown hydrocarbon is 9.10% CO 2 , 8.90% CO, and 82.0%
N 2 (no O 2 is present). Determine
a. The fuel model ðC n H m Þ:
b. The mass percentages of C and H present in the fuel.
c. The molar air/fuel ratio and percent theoretical air used in
the combustion.
d. The dew point temperature at 0.106 MPa.
43.* The Orsat analysis of the (dry) exhaust gas from the combustion
of an unknown hydrocarbon is 1.10% CO 2 , 1.10% CO, 18.8%
O 2 , and 79.0% N 2 : Determine
a) The fuel model ðC n H m Þ,
b) The percent mass composition of the fuel,
c) The fuel/air ratio used, and
d) The dew point temperature at 0.644 MPa.
44.* The combustion of a mysterious unknown hydrocarbon fuel in
the dimensional stabilization module of the temporal drive unit
produces the following Orsat (dry) exhaust gas analysis: 4.50%
CO 2 , 1.90% CO, 14.1% O 2 , and 79.5% N 2 : Determine
a. The fuel model ðC n H m Þ and its probable name.
b. The percent mass composition of the fuel.
c. The percent of theoretical air used in the combustion.
d. The dew point temperature of the exhaust products at
1.00 MPa.
45. A Wingbarton hydrocarbon bomb explodes in the dry air near
an Orsat analyzer. A slightly injured but quick-witted technician
quickly carries out a dry gas analysis in the shattered remains of
the laboratory to produce the following results: 2.80% CO 2 ,
0.500% CO, 16.2% O 2 , and 80.5% N 2 : Determine
a. The fuel model ðC n H m Þ and probable name of the
mysterious hydrocarbon explosive used in the Wingbarton
bomb.
b. The mass percentage composition of the carbon and
hydrogen in the bomb.
c. The percentage of excess air available in the laboratory when
the bomb exploded.
d. The dew point temperature in the lab after the bomb
exploded (assume atmospheric pressure).
46. An international espionage agent uses a computerized pocketsized
Orsat apparatus to grab and analyze a dry sample of the
exhaust gases from the new air-breathing, hydrocarbon-burning,
Blood-Sucker guided missile. The Orsat readout is 6.20% CO 2 ,
2.10% CO, 9.90% O 2 , and 81.8% N 2 : Determine
a. The fuel model C n H m and probable name of the Blood-
Sucker’s fuel.
b. The percentages of carbon and hydrogen by mass in the fuel.
c. The mass fuel/air ratio used by the missile.
47. An ancient internal combustion Mugwump bilge-pump engine
burns a mixture of obscure hydrocarbon fuels that can be
modeled as a single fuel. An Orsat analysis of the dry exhaust
gas from this engine gives the following results: 5.90% CO 2 ,
5.50% CO, 7.50% O 2 , and 81.1% N 2 : Determine
a. The single fuel hydrocarbon model ðC n H m Þ:
b. The carbon and hydrogen composition by mass of this fuel.
c. The percent of theoretical air used in the engine.
48. An Orsat analysis of the combustion of a strange unearthly
hydrocarbon gas produces a (dry) result of 5.00% each for CO 2 ,
CO, and O 2 , with N 2 making up the remainder. Determine
a. The hydrocarbon fuel model C n H m for this strange and
somewhat putrid gas.
b. The mass composition of this gas.
c. The percent of excess air used in the combustion.
49. The coagulated remains of a fiendish mutant humanoid
creature that evolved on an oxygen-free planet are oxidized and
dried in air by a laser beam then processed through a nuclearpowered
Orsat analyzer that reports the following composition,
using a computerized synthetic voice: “Thee ox-see-gin, car-bon
de-oxside and car-bon mo-noxside conzentrations are each
exactly seven per-cent. Thee remaining gaz is nitrogen. Zis is
very unusual.” As chief engineer of the starship Entropy,
determine
a. The synthetic formula ðC n H m Þ of the mutant’s body tissue.
b. The carbon and hydrogen percentages by mass in the tissue.
c. The percent of excess air available in the atmosphere where
the tissue was oxidized.
50. An icky, unknown hydrocarbon fuel of the form ðCH 2 Þ n is
burned with an unknown amount of excess air x in the
following gosh awful reaction:
ðCH 2 Þ n
+ 1:5nð1 + xÞ½O 2 + 3:76ðN 2 ÞŠ
! nðCO 2 Þ + nðH 2 OÞ + 1:5nxðO 2 Þ + 5:64nð1 + xÞðN 2 Þ