※ [本文转录自 NTU-Exam 看板] 作者: youngsam (要加油要加油) 看板: NTU-Exam 标题: [试题] 93下化学系普通化学甲第二次期中考 时间: Fri May 6 23:29:05 2005 课程名称︰普通化学甲下 班次01 限本系学生 课程性质︰必修 课程教师︰牟中原 开课系所︰化学系 考试时间︰2005.05.06 试题 : 九十三学年度 化学系 普通化学甲 第二次期中考 1. The rate law of the reaction (10%) 2NOBr(g) --> 2NO(g) + Br2(g) at some temperture is Rate = - d[NOBr] / dt = k [NOBr]^2 a. If the half-life for this reaction is 2.00s when [NOBr]0 = 0.900M, calculate the value of k for this reaction. b. How much time is required for the concentration of NOBr to decrease to 0.100M ? 2. The following mechanism has been proposed to account for the rate law of the decomposition of ozone to O2(g): (8%) k1 O3 + M <----> O2 + O + M k-1 k2 O + O3 -----> 2 O2 Apply the steady-state hypothesis to the concentration of atomic oxygen, and derive the rate law for the decomposition of ozone.(M stands for an atom or molecule) 3. A solution is prepared by mixing 0.0300 mol CH2Cl2 and 0.0500 mol CH2Br2 at 25℃. Assuming the solution is ideal, calculate the composition of the vapor (in terms of mole fractions) at 25℃. At 25℃, the vapor pressure of pure CH2Cl2 and pure CH2Br2 are 133 and 11.4 torr, respectively. (8%) 4. Complete and balance the following reactions. (12%) a. Rb(s) + H2O(l) ---> b. Na2O2(s) + H2O(l) ---> c. LiH(s) + H2O(l) ---> d. KO2(s) + H2O(l) ---> e. PbS + O2 ---> f. BF3 + NH3 ---> 5. A compound that contains only C and H was burned in excess O2 to give CO2 and H2O. When 0.270g of the compound was burned, the amount of CO2 formed reacted completely with 20.0mL of 2.00M NaOH solution according to the equation 2OH^-(aq) + CO2(g) ---> CO3^2-(aq) + H2O(l) When 0.270g of the compound was dissoloved in 50.0g of camphor, the resulting solution had a freezing point of 177.9℃. (15%) [ Pure camphor freezes at 179.8℃ and has Kf=37.7 ℃ kg/mol ] a. What is the empirical formula of the compound? b. What is the molecular mass of the compound? c. What is the molecular formula of the compound? 6. A group 3A metal has a density of 2.70 g/cm^3 and a cubic unit cell with an edge length of 404 pm. Reaction of a 1.07 cm^3 chunk of the metal with an excess of hydrochloric acid gives a colorless gas that occupies 4.00L at 23.0℃ and a pressure of 740 mm-Hg (15%) a. Identify the metal. b. Is the unit cell primitive, bodt-centered, or face-centered? c. What is the atomic radius of the metal atom? 7. In deep sea diving, in the air used by the diver nitrogen is replaced by helium. (10%) a. Please explain why one use helium. b. What are the side effects of using helium? 8. Please draw the phase diagram of water to show: a. Critical point b. Triple point c. at least two solid phases d. Draw the temperture vs. time curve at a constant pressure of 1 atm from 240K to 400K as one heats a sample of ice until to vapor. e. Draw the corresponding T vs. t curve but at a pressure above critical pressure. (10%) 9. A cellulose is a kind of carbohydrates. If 200.0ml of aqueous solution containing 1.500g of cellulose at 300K gives rise of an osmotic rise of solution level of h=20.4cm, calculate the molecular weight of this cellulose. Assume the density of the solution is 1.000 g/cm^3. (12%) --

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