课程名称︰普通化学甲下
课程性质︰物理系、材料系大一必带
课程教师︰金必耀
开课学院：理学院
开课系所︰化学系
考试日期（年月日）︰2019/06/21
考试时限（分钟）：120分钟
是否需发放奖励金 : 是
试题 :
Final Exam
Problem 1.
A physician wishes to prepare a buffer solution at pH = 3.82 that if ciently
resists changes in pH yet contains only small concentrations of the buffering
agents. Determine which one of the following weak acids, together with its
sodium salt, would probably be best to use: m-chlorobenzoic acid, Ka = 1.04e-4
; p-chlorocinnamic acid Ka = 3.89e-5 ; 2,5-dihydroxybenzoic acid, Ka = 1.08e-3
; or acetoacetic acid, Ka = 2.62e-4. Explain.
Problem 2.
Thiamine hydrochloride (vitamin B_1 hydrochloride, HC12H17ON14SCl2) is a weak
acid with Ka = 3.4e-7. Suppose 3.0e-5 g of thiamine hydrochloride is disolved
in 1.00 L of water. Calculate the pH if the resulting solution. (Hint: This is
a sufficiently dilute solution that the autoionization of water cannot be
neglected.)
Problem 3.
Consider the two following nitrophenol structures:
OH OH
∣ ∣
／＼ ／＼
∣O ∣ ∣O ∣
＼／ ＼／＼
∣ N0_2
N0_2
p-nitrophenol m-nitrophenol
Predict which will be the stronger acid. Explain your prediction.
Problem 4.
A Zn|Zn^{2+}||Co^{2+}|Co galvanic cell is constructed in which the standard
cell potential is 0.48V. Calculate the free energy change at 25度C per gram
of zinc lost at the anode, if all concentrations remain at their standard
value of 1 M throughout the process. What is the maximum electrical work done
by the cell on its surroundings during this experiment?
Problem 5.
(a.) The concentration of the electrolyte, sulfuric acid, in a lead-acid
storage battery diminishes as the battery is discharged. Is a discharged
battery recharged by replacing the dilute H_2SO_4 with fresh, concentrated
H_2SO_4? Explain.
(b.) One cold winter morning the tmperature is well below 0度F. In trying to
start yout car, you run the battery down completely. Several hours later, you
return to replace yout fouled spark plugs and find that the liquid in the
battery has now frozen even though the air temperature is actually a bit
higher that it was in the morning. Explain how this happen.
Problem 6.
By considering these half-reactions and their standard reduction potential,
Pt^{2+} + 2e- → Pt E = 1.2 V
NO3- + 4H3O+ + 3e- → NO + 6H20 E = 0.96 V
PtCl4^{2-} + 2e- → Pt + 4Cl- E = 0.73 V
account for the fact that platinum will dissolve in a mixture of hydrochloric
acid and nitric acid (aqua regia) but will not dissolve in either acid alone.
Problem 7.
The decomposition of ozone by light can be described by the mechanism
O3+light —k1→ O2 + O
O+O2+M —k2→ O3 + M
O+O3 —k3→ 2O2
with the overall reaction being
2O3+light → 3O2
The rate constant k1 depends on the light intensity and the type of light
source used. By making a steady-state approximation for the concentration of
oxygen atoms, express the rate of formation O2 in terms of the O2, O3, and M
concentrations and the elementary rate constants. Show that only the ratio
k3/k2, and not the individual values of k2 and k3, affects the rate.
Problem 8.
Hemoglobin molecules in blood bind oxygen and carry it to cells, where it
takes part in metabolism. The binging of oxygen
hemoglobin(aq) + O2(aq) → hemoglobinO2(aq)
is first order in hemoglobin and first order in dissolved oxygen, with a rate
constant of 4e7 L mol^{-1} s^{-1}. Calculate the initial rate at which oxygen
will be bound to hemoglobin if the concentration of hemoglobin is 2e-9 M and
that of oxygen is 5e-5 M.
Problem 9.
The enzyme lysozyme kills certain bacteria by attacking a suger called
N-acetylglucosamine(NAG) in their cell walls. At an enzyme concentration of
2e-6 M, the maximum rate for substrate (NAG) reaction, found at high
substrate concentration, is 1e-6 mol L^{-1} s^{-1}. The rate is reduced by a
factor of 2 when the substrate concentration is reduced to 6e-6 M. Determine
the MichaelisMenten constants Km and k2 for lysozyme.
Problem 10.
Consider the following nuclear decay
64 64 0
Cu → Zn + β t = 12.8 h
-1 1/2
Starting with one mole of 64Cu, calculate the number of grams of 64Zn formed
after 25.6 hours.
Problem 11.
The rate-determining step of the bromination of acetone involves breaking a
carbonhydrogen bond. Estimate the ratio of the rate constants kC-H/kC-D for the
reaction at 300K. The wave-numbers of vibration for the particular bonds are
ν'C-H ～3000 cm^{-1} and ν'C-D ～2100 cm^{-1}. (The wavenumber ν' is given
by ν/c, where ν is the frequency and c is the velocity of light.)
Problem 12.
Consider the following parallel first-order reactions:
A —k1→ B
A —k2→ C
(a.) Write the expression for d[B]/dt at time t, given that [A]0 is the
concentration of A at t=0.
(b.) What is the ratio of [B]/[C] upon completion of the reactions.