[試題] 102上 林英智 普通化學乙上 第一次期中考
課程名稱︰普通化學乙上
課程性質︰必修
課程教師︰林英智
開課學院：生農學院
開課系所︰森林環資系
考試日期（年月日）︰2013/10/16
考試時限（分鐘）：110分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Atomic mass: Br 80, Ca 40, Cl 35.5, Na 23, P 31, S 32
Gas constant: 8.315JK^-1mol^-1 = 8.206 ×10^-2 LatmK^-1mol^-1
1.(10 points) Naturally occuring magnesium has atomic mass of 24.312 and
consists of three isotopes. The major isotope is 24Mg, natural abundance
78.99%, relative atomic mass 23.98504. The next most abundant isotope is
26Mg, relative atomic mass 25.98259. The third most abundant isotope is
25Mg, whose natural abundance is in the ratio of 0.9083 to that of 26Mg.
Find the relative atomic mass of 25Mg.
2.(5 points) A mixture of 50.0 g of sulfur and 1.00 ×10^2 g chlorine molecule
reacts completely to form S2Cl2 and SCl2. Find the mass of S2Cl2 formed.
3.(10 points) Hard water often contains dissolved calcium and magnesium ions.
One way to soften water is to add phosphates. The phosphate ion forms
insoluble precipitates with calcium and magnesium ions, removing them from
solution. A solution is 0.050 M in calcium chloride and 0.085 M in magnesium
nitrate. Assume complete reaction, what mass of sodium phosphate would have
to be added to 1.5 L of this solution to completely eliminate the hard water
ions?
4.(10 points) In a given diffusion apparatus 15.0 mL of hydrogen bromide gas
diffused in 1.0 min. In the same apparatus and under the same conditions,
20.3 mL of an unknown gas diffused in 1.0 min. The unknown gas is a
hydrocarbon. Find its molecular formula.
5.(15 points) The atmosphere slowly oxidizes hydrocarbons in a number of steps
that eventually convert the hydrocarbon into carbon dioxide and water. The
overall reaction of a number of such steps for methane gas is
CH4(g) + 5 O2(g) + 5 NO(g) → CO2(g) + H2O(g) + 5 NO2(g) + 2 OH(g)
Suppose that an atmospheric chemist combines 155 mL of metheane at STP, 885
mL of oxygen at STP, and 55.5 mL of nitrogen monoxide at STP in a 2.0 L
flask. The flask is allowed to stand for several weeks at 275K. If the
reaction reaches 90.0 % of completion for the limiting reagent, what is the
partial pressure of oxygen molecule and carbon dioxide? What is the total
pressure?
6.(10 points) A steel cylinder contains 5.00 mol of graphite (pure carbon) and
5.00 mol of O2. The mixture is ignited and all the graphite reacts.
Combustion produces a mixture of CO and CO2 gas in additional to remaining
O2. After the cylinder has cooled to its original temperature, it is found
that the pressure of the cylinder has increased by 17.0 %. Calculate the
mole fractions of CO, CO2 and O2 in the final mixture.
7.(5 points) Air has carbon monoxide levels of 15.0 ppm. An average human
inhales about 0.50 L of air per breath and takes about 20 breaths per
minute. How many milligrams of carbon monoxide does the average person
inhale in an 8-hour period at this level of carbon monoxide pollution?
Assume that the carbon monoxide has a density of 1.2gL^-1.
8.(10 points) Find ΔE, ΔH, q, and w for the change in state of 1.0 mol H2O(l)
at 80°C to H2O(g) at 110°C. The heat capacity of H2O(l) = 75.3 Jmol^-1K^-1,
and the heat of vaporization of water is 40.7 ×10^3 Jmol^-1 at 100°C.
9.(15 points) Consider 2.00 mol of a monatomic ideal gas that is taken from
state A (PA = 2.00 atm, VA = 10.0 L) to state B (PB = 1.00 atm, VB = 30.0 L)
by two different pathways:
Pathway I. state A (PA = 2.00 atm, VA = 10.0 L) to state C (PC = 2.00 atm,
VC = 30.0 L) by a constant pressure process, then by a constant volume
process to state B (PB = 1.00 atm, VB = 30.0 L);
Pathway II. state A (PA = 2.00 atm, VA = 10.0 L) to state D (PD = 1.00 atm,
VD = 10.0 L) by a constant volume process, then by a constant pressure
process to state B (PB = 1.00 atm, VB = 30.0 L).
Calculate ΔE, q, and w for both pathways.
10.(10 points) The ΔHf° of TiI3(s) is -328 kJmol^-1 and the ΔH° for the
reaction
Ti(s) + I2(g) → TiI3(s) (unbalanced)
is -839 kJ. Calculate the ΔH of sublimation of iodine molecule, which is a
solid at 25°C.
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10/17 23:03, , 1F
10/17 23:03, 1F