课程名称︰普通化学丙
课程性质︰必修
课程教师︰刘铭璋
开课学院：理学院
开课系所︰化学系
考试日期（年月日）︰103/12/3
考试时限（分钟）：110分钟
试题 :
Midterm Exam of General Chemistry 12/03/2014
1. Which of the following statements of benzene (C6H6) are true? (6%)
(a) All six C─C bonds are known to be equivalent.
(b) We can use the localized electron model to describe the σ bonding and the
molecular orbital model to describe the bonding.
(c) All carbon atoms in benzene are sp^3 hybridized.
(d) Benzene contains only π bonds between C atoms.
(e) There are six p orbitals to form π molecular orbitals.
(f) The electrons in the resulting molecular orbitals are delocalized above and
below the plane of the ring.
(g) The delocalized Tt electrons account for the electrical conductivity of
benzene.
2. For the reaction, the equilibrium constant K is 1.3 x 10^8 at 25℃.
http://ppt.cc/xBE0
Which of the following statements are true? (4%)
(a) This reaction is likely to be a good source of the products at 25℃.
(b) K depends on the initial concentrations of the reactants.
(c) This is an endothermic reaction.
(d) K for the reaction will be larger at 25℃ than at 500℃.
(e) Addition of D will cause [A] to increase.
(f) Raising the pressure will cause [C] to increase.
(g) Lowering the volume of the container has no effect on K.
(h) Catalysts are an effective means of changing the position of an equilibrium.
3. Which of the following statements are typically true for a reaction? (5%)
(a) The catalyst provides a new pathway with higher activation energy in the
reaction mechanism.
(b) The concentration of the catalyst will go down as a reaction proceeds.
(c) An enzyme is typically a large protein molecule that contains one or more
active sites where interactions with substrate take place.
(d) In enzyme catalysis, the rate rises rapidly with increasing substrate
concentration initially. Above a certain substrate concentration, the rate
is zero order in the substrate.
(e) Kinetic measurements are often made under conditions where the reverse
reaction is significant.
(f) Rate law for the elementary step can be written from the molecularity of
the reaction.
(g) For a successful formation of a product according to the collision model,
the energy of the incoming particles must be above a certain minimum value,
and the relative orientation of the particles must allow for formation of
new bonds in the product.
(h) Transition state is the arrangement of atoms found at the top of the
potential energy barrier as a reaction proceeds from reactants to products.
4. (1) Write Lewis structures for each of the following molecules. (2) Also
predict the molecular structures and bond angles. (3) Give the expected
hybridization of the central atom. (4) Which of the molecule is not polar?
(a) NCl3, (b) CIF3, (c) IF5. (10%)
5. Describe the bonding in NO+, NO, and NO, using both the localized electron
and molecular orbital models. Account for any discrepancies (ex: magnetism,
bond order) between the two models. (12%)
6. Identify the most important types of intermolecular forces present in the
solids of each of the following substances. (6%)
(a) CO2 (b) SiO2 (c) NaCl (d) Au (e) HF (f) fullerene
7. The radius of gold is 144 pm, and the density is 19.32 g/cm^3. Does
elemental gold have a face-centered cubic structure or a body-centered cubic
structure? Au: 197.0 g/mol (10%)
8. Draw the molecular orbital energy level (band model) of magnesium crystal.
Do all of the core and valence atomic orbitals overlap and mix to form
molecular orbitals? Use band model to explain the typical physical
properties of metals: malleability, ductility, and the uniform conduction of
heat and electricity in all directions. (8%)
9. At a particular temperature, K: 2.0 x 10^-6 for the reaction
http://ppt.cc/1wI5
If 2.0 moles of CO2 is initially placed into a 5.0-L vessel, calculate the
equilibrium concentrations of all species. (8%)
10.Consider the following reaction at 500K: http://ppt.cc/Wen~
An equilibrium mixture contains 1.0 mole of Fe, 1.0 x 10^-3 mole of O2, and
2.0 moles of Fe2O3 all in a 2.0-L container. Calculate the value of K for
this reaction. Could equilibrium constant of this reaction express by
pressure? If yes, calculate K_p. (7%)
11.Iodomethane (CH3I) is a commonly used reagent in organic chemistry. When
used properly, this reagent allows chemists to introduce methyl groups in
many different useful applications. The chemical does pose a risk as a
carcinogen, possibly owing to iodomethane's ability to react with portions
of the DNA strand (if they were to come in contact). Consider the following
hypothetical initial rates data:
http://ppt.cc/FOjm
Determine the rate law and rate constant.
Which of the following could be a possible mechanism to explain the initial
rate data? Justify your choice. (8%)
http://ppt.cc/2d1X
12.The following data were collected in two studies of the reaction 2A+B → C+D
http://ppt.cc/g6YX
In Experiment 1, [B]_0 = 5.0 M. In Experiment 2, [B]_0 = 10.0 M.
-Δ[A]
Rate = ─────
Δt
a. Why is [B] much greater than [A]?
b. Give the rate law and value for k for this reaction.
c. Calculate the concentration of A in Experiment 2 at t 140 s. (8%)
13.One mechanism for the destruction of ozone in the upper atmosphere is
http://ppt.cc/feTi
(a) Which species is a catalyst?
(b) Which species is an intermediate?
(c) Specify which step is the rate-determining step.
(d) E_a for the uncatalyzed reaction O3(g) + O(g) → 2O2(g)
is 14.0 kJ. E_a for the same reaction when catalyzed is 11.9 kJ. What is
the ratio of the rate constant for the catalyzed reaction to that for the
uncatalyzed reaction at 25℃? Assume that the frequency factor A is the
same for each reaction. (8%)