Modern Engineering Thermodynamics

Problems 645
where j = 4n + m kgmole electrons per kgmole of C n H m and F = 96,487 kJ/(V·kgmole electrons) is Faraday’s
constant.
19. Fuel cell electrical current:
I = ð _n fuel ÞjF
20. The specific molar flow availability of chemical species i:
½ða f Þ i
Š chemical
= g • i
+ RT ln p i
p°
Problems (* indicates problems in SI units)
1.* Determine the mass in kg of one molecule of water.
2. Determine the mass in lbm of one molecule of methane.
3.* The density of benzene ðC 6 H 6 Þ is 879 kg/m 3 . Determine the
volume of
a. 1 kgmole of benzene.
b. 1 molecule of benzene.
4. Determine the percentage by mass of carbon in C 8 H 18 :
5. Determine the percentage by mass of aluminum in Al 2 O 3 :
6. Determine the percentage by mass of oxygen atoms in a
molecule of casein of milk, C 708 H 1130 O 224 N 180 S 4 P 4 :
7. Determine the percentage by mass of carbon, hydrogen, and
oxygen in methyl alcohol, CH 3 ðOHÞ:
8. The spectral analysis of a chemical compound gave the
following composition on a mass basis: 29.1% Na, 40.5% S,
30.4% O. Determine the chemical formula of this substance
(i.e., find x, y, and z in Na x S y O z ).
9. How many lbm are in 1 lbmole of
a. C 12 H 22 O 11 (sucrose, a typical carbohydrate).
b. C 57 H 110 O 6 (stearin, a typical fat).
c. C 3032 H 4816 O 872 N 780 S 8 Fe 4 (human hemoglobin, a typical
protein).
10.* Convert the following to mass units (kg or lbm): (a) 1.00
kgmole of CO 2 , (b) 2.00 × 10 −3 lbmole of Fe 2 O 3 , (c) 6.00
gmoles of SO 2 , (d) 0.700 kgmole of CH 4 :
11.* Convert the following to molar units (kgmole or lbmole):
(a) 14.0 lbm of CO, (b) 0.370 kg of H 2 O, (c) 123 g of C 2 H 2 ,
(d) 5.00 kg of C 8 H 18 :
12.* When 2.00 kgmoles of KClO 3 are heated, 2.00 kgmoles of KCl
and 3.00 kgmoles of O 2 are produced. If 50.0 kg of KClO 3 are
heated, how many kg of KCl and O 2 are produced?
13. Determine the reaction equation and molal analysis of the
combustion products for the combustion of carbon disulfide,
CS 2 , with
a. 100.% theoretical air.
b. 150.% theoretical air.
c. An air/fuel ratio of 47.6 moles of air per mole of fuel to
produce CO 2 ,SO 2 , and excess air products.
14. Determine the reaction equation and molal analysis of the
combustion products of ammonia, NH 3 , on the surface of a
heated platinum wire in the presence of
a. 0.00% excess oxygen.
b. 125% theoretical oxygen.
c. 25.0% deficit oxygen to form NO, H 2 O, and excess air
products.
15. Determine the reaction equation and volumetric analysis of the
combustion products for the combustion of methyl alcohol,
CH 3 ðOHÞ, with
a. 100.% theoretical oxygen.
b. 150.% theoretical oxygen.
c. 50.0% theoretical oxygen.
16. Determine the reaction equation and volumetric analysis of the
combustion products for the combustion of natural rubber,
½C 3 H 8 Š 2000
or ðC 6000 H 16,000 Þ, with
a. 100.% theoretical oxygen.
b. 400.% excess oxygen.
c. 90.0% deficit oxygen.
17. Determine the reaction equation and molal air/fuel ratio for the
combustion of ethyl alcohol, C 2 H 5 ðOHÞ, with
a. 100.% theoretical air.
b. 100.% excess air.
c. 50.0% deficit air.
18. Determine the reaction equation and molal air/fuel ratio for the
combustion of dimethyl ketone (acetone), COðCH 3 Þ 2
, with
a. 0.00% excess air.
b. 100.% excess air.
c. 30.0% theoretical air.
19. Determine the reaction equation and molar fuel/air ratio for the
combustion of wood cellulose, C 6 H 10 O 5 , with
a. 100.% theoretical air.
b. 250.% excess air.
c. 25.0% deficit air.
20. Determine the reaction equation, molal analysis of the
combustion products, and mass air/fuel ratio for
the combustion of kerosene, C 10 H 22 , with 187%
excess air.
21. Determine the reaction equation, volumetric analysis of the
combustion products, and molal fuel/air ratios for the
combustion of tetraethyl lead, PbðC 2 H 5 Þ 4
, the common
antiknock gasoline additive, to form PbO, CO 2 ,H 2 O, and
possibly excess air with
a. 100.% theoretical air.
b. 10.0% excess air.
c. An air/fuel ratio of 20.0 lbm of air per lbm of fuel.
22. Develop a reaction equation for the combustion of
polyethylene, ½CH 2 CH 2 Š n
, in 100.% theoretical air.
23. A simple alcohol can be obtained from a hydrocarbon by
replacing one of the hydrogen atoms by a hydroxyl group (OH).
Develop a reaction equation for the combustion of a generalized