04级(1)无机化学期中考试试卷

四、（20分）所谓“酸雨”（Acid rain）是指大气中的SO2和NOx被氧化成SO3和NO2

并分别与水反应生成硫酸和硝酸，使雨水的pH为4.5，最低可达1.7。

－

SO2(aq) + H2O(l) HSO3(aq) + H+(aq) Ka1 = 10 –1.92

－

HSO3(aq) SO32– (aq) + H+(aq) Ka2 = 10–7.18

1． 在SO2的分压为1atm时，它在每升水中的溶解度为33.9升（25℃时）

(1) 计算被二氧化硫饱和的水中的二氧化硫总浓度（设SO2溶解后水的体积不变） (2) 计算亚硫酸氢根离子的百分含量 (3) 计算该溶液的pH 2． 计算含0.0100 mol ? dm–3亚硫酸钠水溶液中的氢离子浓度

3． 在亚硫酸氢钠水溶液中存在如下的主要平衡，(1) 计算它的平衡常数

－

2HSO3(aq) SO2 (aq) + SO32– (aq) +H2O(l)

(2) 若只考虑此平衡，计算0.0100 mol ? dm–3亚硫酸氢钠水溶液中的二氧化硫浓度。 4． 亚硫酸钡在水中的溶解度为0.016g/100mL(MBaSO3 = 217.39)，试计算亚硫酸钡的Ksp 5． 亚硫酸银的溶度积为10 –13.87。计算亚硫酸银饱和水溶液中的银离子浓度。 6． 亚硫酸钙的Ksp = 10 –7.17，试求下列反应的平衡常数 Ca2+(aq) + Ag2SO3(s) CaSO3(s) + 2Ag+(aq)

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五、（10分）右图是水的相图。

DCI是 区，II是 区，III是 区，B点是水

的 ，沿着BC线 速率＝ 速

(II)率，所以 相共存。

(III) 一定量的水放在密闭容器中，该容器连接真空泵。打开真

空泵，水首先表现出 ，然后再 。最后会B(I)出现 。试在相图上画出示意图并文字解释为：

ATemperature

。

Additional Exam (20 points)

1. Each of the questions or incomplete statements below is followed by four suggested

answers or completions. Please give your answer that is best in each case.

(1) Which of the following sets of conditions describes a system undergoing a reversible

change? ( ) ?Ssystem ?Ssurronding ?Stotal

(A) positive zero positive (B) positive negative zero (C) positive positive zero (D) negative zero negative

(2) The statement that heat cannot spontaneously flow from a colder to a hotter body is a

resulf of ( ) (A) the first law of thermodynamics (B) the second law of thermodynamics (C) the third law of thermodynamics (D) Le Chatelier’s principle

(3) Benzene and toluene form nearly ideal solutions. The vapor pressure of pure tolecene

is 22torr at 20℃. For an equimolar mixture of benzene and toluene at 20℃ the vapor pressure of toluene is: ( ) (A) 5.5torr (B) 7.3torr (C) 11torr (D) 22torr

(4) Which equation correctly describes the relationship between Kp and Kc for the

following reaction? Cl2(g) + 3F2(g) 2ClF3(g) ( ) (A) Kp = Kc (B) Kp = Kc (RT) –1 (C) Kp = Kc (RT) –2 (D) Kp = Kc(RT) 2

(5) Which of the following reactions would be expected to involve the largest increase in

entropy ? ( ) (A) H2O(l) H2O(g) (B) H2O(s) H2O(l) (C) H2(l) H2(g) (D) He(l) He(g)

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Pressure(6) The reaction, 3NH4+ + BiN(s) Bi3+ + 4NH3 , occurs in liquid ammonia. In this

reaction the amnonium ion behaves as ( ) (A) an oxidizing agent (B) a reducing agent (C) an acid (D) a base

(7) If the solution is not supersaturated, what is the maxinum Bi3+ concentration that can

be reactant without causing precipitation in a solution containing 0.01mol per liter of S2– ? (The Ksp bismuth sulfide may be taken as 1×10–70) ( ) (A) 1×10–72 mol ? dm–3 (B) 1×10–64 mol ? dm–3 (C) 1×10–34 mol ? dm–3 (D) 1×10–32 mol ? dm–3

(8) Which of the following carbonate species would be present in significant

concentrations in a solution of carbonic acid at pH = 10?(For carbornic acid, Ka1 = 3.5×10–7, Ka2 = 7.0×10–11) ( )

－

(A) H2CO3 only (B) H2CO3 and HCO3

－

(C) CO32– only (D) HCO3 and CO32– (9) Which of the following statements is true ?(CdS: Ksp = 8×10–27, CuS: Ksp = 6.3×10–36,

Ag2S: Ksp = 6.3×10–50) ( ) (A) CdS is less soluble than CuS

(B) CdS is about 109 times more soluble than CuS (C) Ag2S is less soluble than either CdS or CuS (D) Ag2S is about 10 time more soluble than CuS

(10) For which of the following reactions change roughly equivalent changes in internal

energy and enthalpy ( )

(A) 2H2(g) + O2(g) 2H2O(g)

(B) Pb(NO3)2(s) + 2KI(s) PbI2(s) + 2KNO3(s)

(C) CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l) (D) NaOH(s) + CO2(g) NaHCO3(g)

2. An organic nitro-compound (RNO2) is electrolytically reduced in aqueous acetate buffer

－

solution having total acetate concentration (HOAc + OAc) 0.500M and pH = 5.0. 300mL of the buffered solution containing 0.01M RNO2 was reduced completely. The dissociation constant for acetic acid is 1.75×10–5 at 25℃. The reduction reaction is

－

RNO2 + 4H+ + 4e RNHOH + H2O

Calculate the pH of the solution on completion of the reduction of RNO2.

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3. “Green” Chemistry ?? The Use of Supercritical CO2

Recently, reactions in supercritical carbon dioxide (critical temperature Tc= 304.3 K; critical pressure pc = 72.8×105 Pa) have received significant attention. The density of a liquid can be easily tuned near the critical point. Moreover, it can be regarded as a ―green‖ solvent that can replace organic solvents. This solvent has actually been used for caffeine extraction for quite a long time. The fact, however, that carbon dioxide has to be compressed is one of the few disadvantages. Real gases can be described by the van-der-Waals equation (although it is still an approximation): constants for CO2: a = 3.59×105 Pa dm6 mol–2 , b = 0.0427 dm3 mol–1

(1) Calculate the pressures needed to achieve a density of 440 g dm–3 at temperatures of

305 K and 350 K.

(2) The use of carbon dioxide both as a solvent and as a reactant instead of phosgene or

carbon monoxide is another example of supercritical processes. Both the catalytic formation of organic carbonates and formamides have already been described. Write a balanced equation of the formation of dimethyl carbonate by the reaction of

methanol with carbon dioxide. How can dimethyl carbonate form if phosgene is the reactant?

(3) From the point of view of ―green chemistry‖ – why should reactions be carried out in

CO2 instead of using carbon monoxide or phosgene (2 reasons)?

(4) Apart from the compression of carbon dioxide, what is the main obstacle in using CO2

as a reactant in comparison to CO or COCl2 (1 reason) ?

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