課程名稱︰普通化學乙
課程性質：化學
課程教師︰梁文傑
開課系所︰化學系開給心理系的
考試時間︰95/1/11 三34
試題 :
Multiple choices: There is only one correct answer in each of the
following equations.
(1) Which of the following solvents is classified as a polar protic solvent?
(a) CH3OH (b) CH3CH2OCH2CH3 (c) CH3COCH3 (d) CCl4
(2) Which of the following descriptions about hydrogen bonds is inapporpriate?
(a) A hydrogen bond is an attractive interaction between an lone pair on an
electronegative atom and a positively polarized H- atom bonded to another
electronegative atom.
(b) Hydrogen bonds must be broken when H2O is frozen to ice.
(c) Hydrogen bond interaction is responsible for the unusually high boiling
point of H2O.
(d) The strength of a hydrogen bond is usually in a range of 2-10 kcal/mole.
(3) Which compound would show the strongest hydrogen bonding interaction with A
ˊ ˋˊ ˋˊ ˋ
│ │ │ │
ˋNˊˋNˊˋNˊ
A
(圖畫不太出來，sorry~ so我用文字敘述的方式，希望能夠看得懂)
本圖是一個恩(加草字頭)，其中下面三個CH換成N，而題目所指的A為中間的N(我也
不知道那個東西是啥，反正不影響作答）(還有，我沒畫雙鍵)
(a) H H H (b) H H (c) H
ˊNˋˊNˋˊNˋ ˊNˋˊNˋˊNˋ ˊNˋˊNˋˊNˋ
│ │ │ │ │ │ │ │ │ │ │ │
ˋ ˊˋ ˊˋ ˊ ˋ ˊˋ ˊˋ ˊ ˋ ˊˋ ˊˋ ˊ
││ ˊ ˋ││ ˊ ˋ││ ˊ ˋ
O O O
(d) ˊNˋˊNˋˊNˋ （a.b的O接的是雙鍵）
│ │ │ │
ˋ ˊˋ ˊˋ ˊ
│
(4) Which description about acetone, a common solvent, is incorrect?
(a) Acetone is a polar aprotic solvent.
(b) The polarity of acetone partly arises from the following resonance
structures, in which negative charge is destributed to the
electronenegative oxygen atom.
O - O
││(雙鍵) │
C <---> + C
ˊ ˋ ˊ ˋ
H3C CH3 H3C CH3
(c) Because of having similar molecular weight, acetone and CH3CH2OCH3
should have almost identical boiling point.
(d) Acetone can solvate cations more effecitively than anions.
(5) Which statement about the dissolution of NaCl in water is incorrect?
(a) NaCl dissolves to release Na+ and Cl-.
(b) Na+ and Cl- are solvated by H2O molecules.
(c) The freezing point of water will be suppressed to below 0度C.
(d) The boilling point of water will be suppressed to below 100度C.
(6) Among the following descriptions about the concept of solubility, which
one is incorrect?
(a) Not all substances continue to dissolve into a solvent regardless of
amount added.
(b) When the salt solution is satuated, dissolution of the salt stops.
(c) The maximum amount of a substance that will dissolve in a given amount
of a solvent at a given temperature, usually expressed as g/mL, is
called the substance's solubility.
(d) The solubility remains constant when temperature changes.
(7) Which gas deviates most signigicantly from ideal PV/nRT bihavior.
(a) H2S (b) NH3 (c) CH4 (d) He
(8) Which description about a solid is incorrect.
(a) When a solid melts, the entropy increase.
(b) Rod-like molecules（棒狀分子）would have higher chance to give
liquid-crystal phases when melting.
(c) All the solids are crystals（結晶）.
(d) It is possible for a solid to change directly to a gas without going
through the liguid state-a process called sublimination.（昇華）
(9) What is the observation when a NaF solution (0.1 M) is added to a
saturated BaF2 solution (Ksp = 1.8 x 10^-7)?
(a) BaF2 precipitates
(b) NaF precipiates
(c) Both of them precipiates
(d) None of them precipiates
(10) The reaction 3 O2 <=> 2 O3 has deltaH = +68 kacl/mol. Which of the
following descriptions is correct?
(a) The equilibrium constant increases when the temperature increases.
(b) The equilibrium constant decreases when the temperature increases.
(c) The equilibrium constant dose not change when the temperature increase.
(d) The relationship between the equilibrium constant and the temperature
is unpredictable.
(11) Among the following equilibrium equations, in which cases the products
are favored?
(i) S2(g) + 2 H2(g) <=> 2 H2S(g) K=2.8 x 10^-21
(ii) CO(g) + 2 H2(g) <=> CH3OH(g) K=10.5
(iii) Br2(g) + 2 H2(g) <=> 2 BrCl(g) K=58.0
(iv) I2(g) <=> 2 I(g) K=6.8 x 10^-3
(a) i and iv (b) ii and iii (c) all of them (d) none of them
(12) In which cases does the entropy increase?
(i) Molecules escape from the liquid phase into the gas state.
(ii) Molecules are frozen from the liguid phase into crystalline solid.
(iii) Mixing benzene（苯）and toluene（甲苯）to form a solution
(a) i only (b) ii only (c) i and iii (d) i, ii and iii
Problem 1:
Predict the miscibility for each of the following pairs of liquids.
(a) H2SO4 and H2O
(b) Hexane (CH3CH2CH2CH2CH2CH3) and diethyl ether (CH3CH2OCH2CH3)
(c) CH3OH and hexane (CH3CH2CH2CH2CH2CH3)
(d) Acetic acid (CH3CO2H,醋酸) and H2O
Explain your answer and give reasons why they are miscible or not?
Problem 2:
When solute dissolves in water, the melting point of water drops. The
freezing point depression deltaT can be estimated according to the given
equation in which m(solute), the molality, is a concentration of the solute
particles (mol/kg) in the solution. For water, the normal freezing point
is 0度C, and the Kf is 1.86度C kg/mol.
「當溶質溶在水中，會使水的冰點下降。冰點降的程度可用下列方程表示，其中
m(solute)為溶液中質溶顆粒之濃度。正常情形下，水的冰點為0度C。Kf為
1.86度C kg/mol」
deltaT = Kf x m(solute)
(a) What is the freezing point depression for a 0.1 m glucose（葡萄糖）
solution? 「0.1 m 葡萄糖液的冰點下降幾度？」(Hint: substitute the
values into the equation, you can obtain the deltaT.「嘗試代入直接
計算deltaT」)
(b) What is the freezing point of the glucose（葡萄糖）solution?「0.1 m
葡萄糖液的冰點為幾度？」(Hint: reminded that the normal freezing point
is 0度C?)
(c) The freezing point depression for a 0.1 m acetic acid is very similar
to that of 0.1 m glucose solution? Is acetic acid a strong acid? How
could you conclude this result according to the observation.
「0.1 m 葡萄糖液的冰點下降幅與0.1 m 醋酸液近。由此觀察，可否說明醋酸或
弱酸。試解釋之。」
Problem 3 (challenging problem)
Sulfuric acid is a diprotic acid that can be ionized in two steps:
H2SO4 <=> HSO4- + H+ Ka1= very large
HSO4- <=> SO42- + H+ Ka2= 1.3 x 10^-2
The high degree of dissociation in the first step indicates that the first
proton released as a strong acid. However, the second one is much weaker.
(a) Draw the Lewis structure of sulfuric acid
(b) Explain why the second proton released as a weak acid.
(c) Use the equation deltaT = Kf x m(solute) in problem 2, estimate the
deltaT for a 0.1 m of H2SO4
Problem4
(a) Draw the Lewis structure for CCl4
(b) Although C-Cl bond is a polar bond, CCl4 is a non-polar molecule with
the permanent dipole u=0. Provide an explanation for this observation
(c) The 1,2-dichloroethylene exists as cis and trans isomers.
H H H Cl
ˋ==ˊ ˋ==ˊ
ˊ ˋ ˊ ˋ
Cl Cl Cl H
cis trans
Which one should be more polar? Explain your answer
(d) One isomer boils at 47度C while the other at 60度C. Use dipole moments
and symmetry arguments to assign the boiling point to the isomers.
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