課程名稱︰普通化學乙下
課程性質︰系內必帶
課程教師︰金必耀
開課學院：工學院
開課系所︰土木工程學系
考試日期（年月日）︰99/6/25
考試時限（分鐘）：130min
是否需發放獎勵金：是，謝謝
（如未明確表示，則不予發放）
試題 :
1.(6%) Consider the ammonia synthesis reaction N2(g) + 3H2(g) --> 2NH3(g),
where ΔG°= -33.3KJ per mol of N2 consumed at 25℃. For each of the
following mixtures and products at 25℃, predict the direction in which the
system will shift to equilibrium.
a. PNH3=1.00 atm, PN2=1.47 atm , PH2=1.00*10^-2 atm
b. PNH3=1.00 atm, PN2=1.00 atm , PH2=1.00 atm
2.(5%) The overall reaction for the corrosion (rusting) of iron by oxygen is
4Fe(s) + 3O2(g) --> 2Fe2O3(s), calculate the equilibrium constant for the
reaction at 25℃ using the following data.
| Substance | ΔH°f(kJ/mol) | S°(J/mol-K) |
| Fe2O3(s) | -826 | 90 |
| Fe(s) | 0 | 27 |
| O2(g) | 0 | 205 |
3.(4%) Simply describe Le Chatelier's principle and how to predict
qualitatively the charge or shift of the equilibrium constant as the
temperature of the endothermic or exothermic reaction changes.(hint: you
should interpret in words and illustration.)
4.(4%) Show and shortly derive van't Hoff equation. Is there the similar
tendency between van't Hoff equation and Le Chatelier's principle.
5.(8%) Benzene has a melting point of 5.5℃ and the enthalpy of fusion of
10.04kJ/mol. The molar heat capacities at constant pressure for solid and
liquid benzene are 100 and 133 J/mol-K, repectively. For the reaction:
C6H6(l) <---> C6H6(s), calculate ΔS(sys) and ΔS(surr) at 11.0℃ at constant
pressure.
6.(6%) Consider the system: A(g) <---> B(g) at 25℃.
a. Assuming that G°(A) = 8996 J/mol and G°(B) = 11718 J/mol, calculate
equilibrium constant.
b. Calculate the equilibrium pressure that result if 1.00 mol A gas at 1.00
atm and 1.00mol Bgas at 1.00 atm are mixed at 25℃.
7.(7%) A quantitative measure of how efficiently spheres pack into unit cells
is called packing efficiency, which is the percentage of the cell space
occupied by the sphere. Calculate the packing efficiencies of a simple cubic
cell, a body-centered cubic cell, and a face-centered cubic cell.(Hint: the
volume of a sphere is 4πr^3/3, where r is the radius of the sphere.)
8.(7%) Briefly describe the difference among insulator, semiconductor, and
conductor using the energy band picture? State whether silicon would form
n-type or p-type semiconductors with the following element: Ga, Al, As.
9.(7%) The properies of crystalline solids are determined largely by
intermolecular interactions. Explain why diamond is harder than graphite.
Why is graphite an eletrical conductor but diamond is not?
10.(9%) Given the phase diagram of carbon shown below, answer the following
questions:
a. How many triple points are there and what are the phases that can
coexist at each triple point?
b. Which has a higher density, graphite or diamond?
c. Synthetic diamond can be made from graphite. Based on the phase diagram,
how would you do this?
11.(8%) The following diagram shows the variation of the equilibrium constant
with temperature for the reaction: I2(g) <---> 2I(g). Calculate ΔG°, ΔH°
, and ΔS° for the reaction at 872K.
12.(6%) Show that the half-time of a second-order reaction is given by t(1/2)=
1/k[X](0). In what fundamental way does the half-life of a second-order
reaction differ from a first-order reaction?
13.(6%) The reaction 2N2O5(g) --> 4NO2(g) + O2(g) was studied at several
temperatures and the following values of k were obtained. Calculate the
value of Ea for this reaction.
| T(℃) | 20 | 30 | 40 | 50 | 60 |
| k(s^-1) | 2.0*10^-5 | 7.3*10^-5 | 2.7*10^-4 | 9.1*10^-4 | 2.9*10^-3 |
14.(9%) The chart show the relationship of reaction pathway and free energy
(kJ/mol) at 300K.
a. What is the intermediate? What will it happen if catalyst adds? What does
D and E stand for? A --> C is exo- or endothermic reaction? What is the
rate-determining step?
b. Calculate the ΔG° and K for the overall reaction.
c. Set the two differences of energy between A to D and B to E as the
activation energies of each. Calculate the rate constant of the overall
reaction.(Arrhenius factor of the reaction is 2.11*10^-5 s^-1)
15.(8%) The reaction 2NO + O2 --> 2NO2 exhibits the rate law: Rate=k[NO]^2[O2].
Which of the following mechanism is consistent with this rate law?
a. NO + O2 --> NO2 + O slow
O + NO --> NO2 fast
b. NO + O2 <--> NO3 fast equilibrium
NO3 + NO --> 2NO2 slow
c. 2NO --> N2O2 slow
N2O2 + O2 --> 2N2O4 fast
N2O4 --> 2NO2 fast
d. 2NO <--> N2O2 fast equilibrium
N2O2 --> NO2 + O2
O + NO --> NO2 fast
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