課程名稱︰普通化學甲
課程性質︰
課程教師︰蘇志明
開課學院：工學院
開課系所︰化工系
考試日期（年月日）︰96/1/19
考試時限（分鐘）：110分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1.Consider the combustion reaction of the hydrogen gas:
H2(g)+1/2O2(g)<==>H2O(g)
with the help of the related thermodynamic data listed below, answer the
following questions:
(a) Caculate ΔS , ΔH, and ΔG of this reaction at 298K and a constant
presure of 1.00 atm.
(b) Caculate ΔS , ΔH, and ΔG of this reaction at 1000K and a constant
presure of 1 atm.
(c) What would be the theoretical equilibrium constants of the above
reaction at 298K and 1000K, respectively?
(d) Calculate the theoretical maximum temperature that could be reacted
by igniting a mixture of 1 mole of hydrogen and 0.5 mole of oxygen
under 1 atm constant pressure (i.e. a hygrogen-oxygen flame or burner).
The initial system temperature is 298K.(Hint: use Hess's law to set up
a working reaction path)
(e) The same question as in (d), except that we ignite a mixture of 1 mole
of hydrogen and 2.5 mole of the air under 1 atm constant pressure
(i.e. a hydrogen-air flame). The air consists of 20% of oxygen and
80% of nitrogen(in mole fraction),and the initial system tempature
is 298K.
---------------------------------------------------------------------------
Related thermodynamic data:
(i) Molar heat capacities at constant pressure(J/mol) (Assuming that they
are constant over the temparatures we considered):
H2(g)=28.9 O2(g)=29.5 N2(g)=29.0
H20(g)=24.8 H20(l)=75.2
(ii) Thermodynamic data at 298K
Substance ΔH ΔG S
(kJ/mol) (kJ/mol) (kJ/mol)
H2(g) 0 0 131
O2(g) 0 0 205
H20(g) -242 -229 189
H20(l) -286 -237 70
---------------------------------------------------------------------------
2. With the same reaction as in Problem(1), except that the final product
is liquid water:
H2(g)+1/2O2(g)<===>H20(l)
we could set up a fuel cell to generate electromotive force. The half
reactions involved are:
Anode reaction: H2(g) + 20H-(aq)-->2H2O(l) + 2e-
Cathode reaction: 2e- + 1/2O2(g) + H2O-->2OH-(aq)
(a) At 298K and 1 atm, what would be the theoretical electromotive force
of this cell?
(b) What would be the theoretical "maximum" useful work, and also the
theoretical "minimum heat"(i.e. the "useless" energy)that could
be generated by this cell for each mole of H2 being consumed?
3. A silver concentration cell is set up at 25度C with 1.0M AgNO3 in the
left compartment and 1.0M NaCl along with excess AgCl(s) in the right
compartment. The measured cell potential is 0.50V. Calculate the Ksp
value for AgCl at 25度C.
4. Consider two blocks of copper with identical mass, one of them is at
temperature Th, while the other at Tc, with Th >= Tc. If one brings
these two blocks of copper together and waits for them to reach
thermal equilibrium under the condition of constant volume, what
would be the change of entropy for the whole process? Prove that
this process is spontaneous(Note: To get full a credit, you
must show your arguments).
5. If wet silver carbonate is dried in a stream of hot air, the air must
have a certain concentration level of carbon dioxide to prevent silver
carbonate from decomposing by the reaction
Ag2CO3(s)<===>Ag2O(s)+CO2(g)
ΔH for this reaction is 79.1 kJ/mol in the temperature range of 25度C
to 125度C. Given that partial pressure of carbon dioxide in equilibrium
with pure solid silver carbonate is 5.8x10(-3) <次方> torr at 25度C,
calculate the partial pressure of CO2 necessary to prevent decomposition
of Ag2CO3 at 120度C.
---------------------------------------------------------------------------
some constants and equations:
R=1.987 cal/mol-deg = 8.314 J/mol-deg
H=E+PV
G=H-TS
dG=VdP-SdT
ΔG=ΔG+RTln(Q)
For ideal gas: Cp=Cv+R
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 220.139.16.58
※ 編輯: lailight 來自: 220.139.16.58 (02/12 01:15)
※ 編輯: lailight 來自: 220.139.16.58 (02/12 01:15)
※ 編輯: lailight 來自: 220.139.16.58 (02/12 01:18)