課程名稱︰普通化學(甲)
課程性質︰必修
課程教師︰蘇志明
開課學院：工學院
開課系所︰化學工程系
考試日期（年月日）︰2006/12/8
考試時限（分鐘）：110
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Second General Chemistry Examination
1.(a)Calculate the number density of pure oxygen gas at 27*C and 1.0 atm (the
number of oxygen molecules per m^3).
(b)Calculate the collision frequency for an oxygen molecule in a sample of
pure oxygen gas at 27*C and 1.0 atm.Assume that the diameter of an O2
molecule is 0.3nm.
(c)Calculate the total collision frequency for all the oxygen molecules in
1 m^3.
(d)Calculate the mean free path in the above sample.
2.Starting from the van der Waals equation.
[P+a(n/V)^2](V-nb)=nRT.
Derive the appropriate approximated equation, and accordingly explain the
general behaviors of the following two PV/nRT plots for real gases.
(a)As shown in the first plot, why at 200atm ,the PV/nRT values first decline
,and the increase as the pressure becomes higher?
(b)As shown in the second plot, why for a given gas, increasing the
temperature, the PV/nRT values are getting closer to 1 over the pressure
considered?
a,b兩圖分別為 Chemical Principles (Steven S. Zumdahl Fifth edition)
P.170 P.171 的figure 5.22 和5.23
3.The equilibrium constant K(a) for the reaction
[Fe(H2O)6]^+3 + H2O <---> [Fe(H2O)5(OH)]^+2 +(H30)^+1 is 3*10^-3
(a)Calculate the pH of a 0.1M solution of [Fe(H2O)6]^+3.
(b)Calculate the pH necessary for 99% of the iron (III) to be in the from
[Fe(H20)6]^+3.
(c)Will a 1.0 M solution of iron (II) nitrate have a higher or lower
pH then a 1.0 M solution of iron (III) nitrate? Explain.
4.A general buffer solution could be described by the following general acid
dissociation reaction: HA<--->H+ + A- acid dissociation constant K(a)
(a) Derive the Henderson-Hasselbalch equation.
(b)Derive the equation that describes the change rate of the pH value as one
adds additional H+ OH- to the buffer solution .
(c)Starting from part (b),obtain the condition of the optimum buffering
capacity for this buffer solution. What is the pH value of this
optimum-buffering solution?
5.(a)Consider acid solutions in which the contribution of water to the H+
concentration is not negligible . the acid equlibrium reaction is
HA<--->H+ + A- acid dissociation constant K(a).
Derive the exact algebraic equation for [H+] or this aqueous solution.
(b)From the equation, deduce the quantitative conditions that the
contribution of H+ from water could be neglected in the solution systems.
6. For the reaction PCl5<--->PCl3+Cl2
at 600 K the equilibrium constant is 11.5 atm .Suppose that 3.0g of PCl5 is
placed in an evacuated 500 mL bulb, which is then heated to 600K.
a.What would the pressure of PCl5 be if it did not dissociate?
b.What is the partial pressure of PCl5 at equilibrium ?
c.What is the total pressure in the bulb at equilibrium?
d.What is the degree of dissociation of PCl5 at equilibrium?
7.The three consecutive acid dissociation constants of a tri-protic acid,
H3A are :K(a1),K(a2),and K(a3) ,respectively.
One also knows thatK(a1)>>K(a2)>>K(a3).
(a)What would be the pH value of the first titration equivalent point?
Give your detailed derivation procedure.
(b)What would be the pH value of the therd titration equivalent point?
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some constants and related equations:
R=8.31J/K*mol =0.0821L*atm/K*mol
Atomic mass:P=31. Cl=35.5 O=16.0
u(avg)=(8RT/pi M)^(1/2)
Z=4ND^2*{(piRT/M)^(1/2)}/V
ln x =2.3*log x
d/dx (lnu(x))=[1/u(x)]*[du(x)/dx]
d/dx(1/u(x))=-[1/u^2]*[du/dx]
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