推 encorev37383:已收至精華區 06/20 17:25
課程名稱︰普通化學甲下
課程性質︰必修
課程教師︰佘瑞琳
開課學院：
開課系所︰化工系
考試日期（年月日）︰2013/05/10
考試時限（分鐘）：110 mins
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Gas constant: R=8.314 J/mol-K=0.082 L-atm/mol-K
I. Multiple choices questions (2 points per question, 20%)
1.Adding 1.85g Na2SO4 to 500.0ml of saturated aqueous BaSO4:
(a)reduces [Ba2+]; (b)reduces [SO4 2¯]; (c)reduces Ksp of BaSO4 (d)increase
the solubility of BaSO4.
2.Which of the following solids are likely to be more soluble in acidic
solution?
(a)H2C2O4 (b)MgCO3 (c)CaF2 (d)Al(OH)3
3.For the following process, choose that △S is negative, assuming each occurs
at constant temperature.
(a)2NaCl(l)→2Na(l)+Cl2(g) (b)Mg(s)+HCl(aq)→MgCl2(aq)+H2(g)
(c)2NO(g)+O2(g)→2NO2(g) (d)CaO(s)+H2O(l)→Ca(OH)2(s)
4.Which of the following changes in a thermodynamic property would you expect
to find for the reaction Br2(g)→2Br(g) at all temperatures: (19.15)
(a)△H>0 (b)△S>0 (c)△G>0 (d)K>0
5.Which of the following metals will react with the acid indicated.
(a)Ag in HNO3(aq) (b)Au in HNO3(aq) (c)Fe in HCl(aq) (d)Cu in HCl(aq)
6.If a chemical reaction is carried out in a fuel cell, the maximum useful
work that can be obtained is
(a)△H (b)△S (c)T△S (d)△G
7.For a spontaneous redox reaction, which of the following must be true?
(a)Ecell>0 (b)△S>0 (c)△G>0 (d)△H>0
8.For the mixing of ideal gases, which of the following is true? (19.19)
(a)Ecell>0 (b)△S>0 (c)△G>0 (d)△H>0
9.For the reaction 2NO(g)+Cl2(g)→2NOCl(g), △H°=-77.1 KJ/mol,
←
△S°=-121.3 J/mol-K at 25°C.
(a)It's an exothermic reaction.
(b)The entropy of the system increases.
(c)It's a spontaneous reaction at standard states and 25°C.
(d)The rate of the reaction must be very fast according to the thermodynamic
state function.
2+
10.For the half-reaction Hg (aq)+2e¯→Hg(l), E°=0.854 V. This means that
(a)Hg(l) will dissolve in 1M HCl.
2+
(b)Hg(l) will displace Fe(s) from an aqueous solution of Fe ion.
(c)Hg(l) is more readily oxidized than H2(g).
2+ +
(d)Hg (aq) is more readily reduced than H (aq).
II. Problems (80%)
1.A handbook lists the aqueous solubility of lithium phosphate at 18°C as
0.034g Li3PO4/100 ml soln. What is the Ksp of Li3PO4 at 18°C? Write the
equilibrium constant expression first. (6%,p.787)
2.Lead(II) iodide, PbI2, is a dense, golden yellow insoluble solid. Calculate
the molar solubility of PbI2 in 0.10M KI(aq)? (6%,p.788,790)
3.AgNO3(aq) is slowly added to a solution that has [CrSO4]2¯=0.010M and
[Br]¯=0.010M.
(a)Determine the concentration of silver ion needed to precipitate either
AgBr(s) or Ag2CrO4(s).
(b)Which one will precipitate first, AgBr or Ag2CrO4?
(c)Is complete separation of Br¯(aq) and CrO4 2¯(aq) by fractional
precipitation fesible? Briefly explain. (8%,p.796)
Ksp of AgBr=5.0*10^-13, Ksp of Ag2CrO4=1.1*10^-12.
4.What is the molar solubility of Fe(OH)3 in a solution containing 0.100M
C2O4 2¯? For Fe(OH)3, Ksp=4*10^-38, Kf=2*10^20. (6%,p.804)
5.For the reversible reaction, O2(g)+2S 2¯(aq)+2H2O(l)→4OH¯(aq)+2S(s)
←
(a)Write thermodynamic equilibrium constant expression, and then make
appropiate substitutions for activities.
(b)The resulting K is Kp or Kc? (6%,p845)
6.For the reaction at 25°C:2NaHCO3(s)→Na2CO3(s)+H2O(l)+CO2(g)
(a)Calculate △H°,△S°,△G°,and equilibrium constant, K for the reaction
at 25°C.
(b)At what temperature will the reaction become spontaneous at standard
states. (10%,19.55)
---------------------------------------------------------
NaHCO3(s) Na2CO3(s) H2O(l) CO2(g)
---------------------------------------------------------
△H°f(KJ/mol) -951 -1131 -286 -394
△S°(J/mol-K) 102 135 70 214
---------------------------------------------------------
7.A handbook lists the following standard enthalpies of formation at 298K for
cyclopentane, C5H10:
△H°f[C5H10(l)]=-105.9 KJ/mol and △H°f[C5H10(g)]=-77.2 KJ/mol
(a)Calculate the △H°vap for C5H10.
(b)Estimate the normal boiling point for cyclopentane according to the
Trouton's rule.
(c)Estimate △G°for the vaporization of cyclopentane at 298K.
(d)Comment on the significance of the sign of △G°at 298K? (i.e. at
standard states and 298K, will more cyclopentane vaporize or condense?
(8%,19.109)
8.The cell diagram for an electrochemical cell is written as:
Cu(s)|CuSO4(aq)∥FeCl3(aq),FeCl2(aq)|Pt(s)
(a)Indicate the half-reaction that occur at the anode and cathode. Balancee
the overall cell reaction.
(b)Indicate the direction of electron flows.
(c)What is the value of E°cell at 298K?
(d)What is the equilibrium constant K for the reaction at 298K.
(e)What is the value of Ecell when the reaction reaches equilibrium.
(10%,p.879)
9.A voltage cell is constructed as follows:
Ag(s)|Ag(sat'd Ag2CrO4)∥Ag(0.125M)|Ag(s).
What is the value of Ecell? For Ag2CrO4, Ksp=1.1*10^-12. (6%,20.45)
10.The chlor-alkali process. According to the diaphragm chlor-alkali cell
shown as figure,
+ -
______◢███◣______
| | | |
| | Battery| |
| |________| |
| |
| |
| | | | | |
▁▁▁▁▁|▁▁| ↑ |▁▁▁▁▁|▁▁▁▁▁| ↑ |▁▁▁
▏ | ▏ | ▏
▏ | ▏ | ▏
▏ | ︴ | ▏
----------|----------------︴ | ▏
▏ | ◢ ︴ | ▏
▏ |◢▉ ︴ | ▏
▏ ◢▉▉ ︴ | ▏
▏ ◢▉▉▉ |___| ▏
▏ ▉▉▉▉ ︴ ▏
▏ ▉▉▉▉ ︴ ▏
▏ ▉▉▉▉ NaCl(aq) ︴ ▏
▏ ▉▉▉▉ ︴ ▏
▏ ▉▉▉▉ ︴ ▏
▏ ▉▉▉◤ ︴ ▏
▏ ▉▉◤ ︴ ▏
▏ ▉◤ ︴ ▏
▏ ◤ ︴ ▏
▏ ︴ ▏
======================================================
(a)Show the anode and cathode compartments as well as negative and positive
electrodes.
(b)Write the balanced chemical equations that occur on anode and cathode,
separately.
(c)What are the high value products will be produced?
(d)What's the purpose of the diaphragm used? (10%,p.902)
11.The standard enthalpy and entropy of a reaction can be determined directly
from the emf as a function of temperature, which gives us a noncalorimetric
method for the calculation of these important thermodynamic quantities.
Assuming that both △H°and △S°are independent of temperature, deduce the
following equation: (4%)
E°cell,T2 = E°cell,T1 + △S°(T2-T1)/zF
------------------------------------------------------------------------------
TABLE 20.1‧Standard Reduction Potential in Water at 25℃
E°red(V) Reduction Half-Reaction
──────────────────────────────
- -
+2.87 F2(g)+2e →2F(aq)
- + - 2+
+1.51 MnO4(aq)+8H(aq)+5e →Mn(aq)+4H2O(l)
- -
+1.36 Cl2(g)+2e →2Cl(aq)
2- + - 3+
+1.33 Cr2O7(aq)+14H(aq)+6e →3Cr(aq)+7H2O(l)
+ -
+1.23 O2(g)+4H(aq)+4e →2H2O(l)
- -
+1.06 Br2(l)+2e →2Br(aq)
- + -
+0.96 NO3(aq)+4H(aq)+3e →NO(g)+2H2O(l)
+ -
+0.80 Ag(aq)+e →Ag(s)
3+ - 2+
+0.77 Fe(aq)+e →Fe(aq)
+ -
+0.68 O2(g)+2H(aq)+2e →H2O2(aq)
- - -
+0.59 MnO4(aq)+2H2O(l)+3e →MnO2(s)+4OH(aq)
- -
+0.54 I2(s)+2e →2I(aq)
- -
+0.40 O2(g)+2H2O(l)+4e →4OH(aq)
2+ -
+0.34 Cu(aq)+2e →Cu(s)
+ -
0[defined] 2H(aq)+2e →H2(g)
2+ -
-0.28 Ni(aq)+2e →Ni(s)
2+ -
-0.44 Fe(aq)+2e →Fe(s)
2+ -
-0.76 Zn(aq)+2e →Zn(s)
- -
-0.83 2H2O(l)+2e →H2(g)+2OH(aq)
3+ -
-1.66 Al(aq)+3e →Al(s)
+ -
-2.71 Na(aq)+e →Na(s)
+ -
-3.05 Li(aq)+e →Li(s)
──────────────────────────────
------------------------------------------------------------------------------
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