課程名稱︰普通化學乙上
課程性質︰系定必修
課程教師︰陳逸聰
開課學院：
開課系所︰材料系
考試日期（年月日）︰2008年1月15日
考試時限（分鐘）：160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. Combustion reactions involve reacting a substance with oxygen. When
compounds containing carbon and hydrogen are combusted, carbon dioxide and
water are the products. Using the enthalpies of combustion for C4H4(-2341
kJ/mol), C4H8(-2755 kJ/mol), and H2(-286 kJ/mol), calculate ΔH for the
reaction (6%)
C4H4(g) + 2H2(g) -> C4H8(g)
2. For the reaction at 298K,
2NO2(g) <-> N2O4(g)
the value of ΔH^0 and ΔS^0 are -58.03 kJ and -176.6 J/K, repectively,
(a) What is the value of ΔG^0 at 298K? (3%)
(b) Assuming that ΔH^0 and ΔS^0 do not depend on temperature, at what
temperature is ΔG^0 =0? (3%)
(c) Is ΔG^0 negative above or below this temperature? (3%)
3. Cells use the hydrolysis of adenosine triphosphate, abbreviated ATP, as a
source of energy. Symbolically, this reaction can be represented as
ATP(aq) + H20(l) -> ADP(aq) + H2PO4-(aq)
where ADP represents adenosine diphosphate. For this reaction ΔG^0 = -30.5
kJ/mol.
(a) Calculate K (equilibrium constant) at 25℃. (4%)
(b) If all the free energy from the metabolism of glucose
C6H12O6(s) + 6O2(g) -> CO2(g) + 6H2O(l)
goes into the production of ATP, how many ATP molecules can be produced
for every molecule of glucose? (4%) (Give ΔG^0_f for C6H12O6, CO2, H2O)
4. Consider the relationship:
ln(K) = -ΔH^0/RT + ΔS^0/R
The equilibrium constant for some hypothetical process was determined as a
function of temperature (in Kelvin) with the results plotted below.
__________________
| 40 __________ |
| |\ | | | |
| 30|_\_|___|__| |
| | \| | | |
| 20|___|\__|__| |
| | | \ | | |
| 10|___|__\|__| |
|lnK | | |\ | |
| |___|___|_\| |
| 1.0 2.0 3.0|
| 1000/T(K) |
|_________________|
From the plot,
(a) determine the values of ΔH^0 and ΔS^0 for this process. (8%)
(b) What would be the major difference in ln(K) versus 1/T plot for an
endothermic process as compared to an exothermic process? (4%)
5. (a) Use
ln(K) = -ΔH^0/RT + ΔS^0/R
to determine ΔH^0 and ΔS^0 for the autoionization of water: (8%)
H20(l) <-> H+(aq) + OH-(aq)
T(℃) K
--------------------------
0 1.14 x 10^-15
25 1.00 x 10^-14
35 2.09 x 10^-14
40 2.92 x 10^-14
50 5.47 x 10^-14
(b) Estimate the value of ΔG^0 for autoionization of water at its critical
temperature, 374℃. (4%)
6. Using the following data, calculate the value of Ksp for Ba(NO3)2, one of
the least soluble of the common nitrate salts. (6%)
Species ΔG^0_f
----------------------------
Ba2+(aq) -561 kJ/mol
NO3-(aq) -109 kJ/mol
Ba(NO3)2(s) -797 kJ/mol
7. (a) Entropy can be calculated by a relationship prosposed by Ludwig
Bloltzmann:
S = k_B lnΩ
where k_B = 1.38 x 10^-23 J/K and Ω is the number of ways a
particular state can be obtained. (This equation is engraved on
Boltzmann's tombstone.) Calculate S for the three arrangements of
particles in the following Table. (6%)
I left:ABCD right:x
II left:BCD right:A left:ACD right:B
left:ABD right:C left:ABC right:D
III left:AB right:CD left:BC right:AD
left:AC right:BD left:BD right:AC
left:AD right:BC left:CD right:AB
(ABCD are all gas particles.)
(b) The standard entropy values (S^0) for H20(l) and H20(g) are 70
JK^-1mol^-1 and 189 JK^-1Mol^-1, respectively. Calculate the ratio of
Ωg to Ωl for water using Boltzmann's equation. (4%)
8. (a) Combine the equations
ΔG^0 = -nFε^0 and ΔG^0 = ΔH^0 - TΔS^0
to derive an expression for ε^0 as function of temperature. Despite
how one can graphically determine ΔH^0 and ΔS^0 from measurements
ε^0 of at different temperatures. Assume that ΔH^0 and ΔS^0 do not
depend of temperature. (5%)
(b) Calculate ε^0 for the reaction (5%)
CH3OH(l) + 3/2O2(g) -> CO2(g) +2H2O(l)
(c) Will ε^0 increase or decrease with an increase in temperature? (5%)
Substance ΔG^0(kJ/mol) S^0_f(JK^-1mol^-1)
-------------------------------------------------------
CH3OH(l) -166 127
O2 0 205
CO2(g) -394 214
H2O(l) -237 70
9. The overall reaction in the lead storage battery is
Pb(s) + PbO2(s) +2H+(aq) +2HSO4-(aq) -> 2PbSO4(s) + 2H2O(l)
(a) Calculate ε at 25℃ for this battery when [H2SO4] = 4.5 M: that is,
[H+] = [HSO4-] = 4.5 M. At 25℃, ε^0 = 2.04 V for the lead storage
battery. (4%)
(b) For the cell reaction ΔH^0=-315.9kJ and ΔS^0=263.5 J/K. Calculate
ε^0 at -20℃. (3%)
(c) Calculate ε at -20℃ when [H2SO4] = 4.5 M. (3%)
(d) Based on your previous answers, why does it seem that batteries fail
more often on cold days than on warm days? (2%)
10. (a) Write out the two half-reactions for a mercury battery. (4%)
(b) In the electrolysis of an aqueous solution of sodium chloride, we have
two possible reactions of
2Cl- -> Cl2 + 2e- -ε^0 = -1.36V
2H20 -> O2 + 4H+ 4e- -ε^0 = -1.23V
to occur in the anode. Which one do you think will happen? Explain
why. (6%)
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