課程名稱︰普化丙
課程性質︰
課程教師︰鄭淑芬
開課系所︰機械系
考試時間︰2006年 6月8日
試題 :
Single Choice Questions:
14% 2 points per question
1. The degradation of phosgene(COCL2)(g) into CO(g) and Cl2(g) happens to
be nonspontaneous at room temperature and standard state conditions
(273K,1atm). What change in temperature must occur to make this a
spontaneous reaction?
(a) increase T
(b) decrease T
(c) add CO to the COCl2
(d) there is insufficient data to answer
2. Two 6.5L flasks are joined by a 150ml tube with a stop cock. If 0.25 moles
of nitrogen are held in the left flask and the right flask is empty , what
happens to the entropy of the system upon opening the valve between the
flasks?
(a) The entropy increases
(b) The entropy remains the same
(c) The entropy decrease
(d) There is too little information to asssess the change
3. Without detailed calculations, predict the sign of △S for the system for:
Fe(s) + 2HCl(g) → FeCl2(s) + H2(g)
(a) positive
(b) negative
(c) zero
(d) too little information to access the change
4. Consider the elementary step: A+B→C. What type of elementary step is this?
(a) unimolecular
(b) bimolecular
(c) termolecular
(d) first order
5. The unit of second order rate constant is
(a) M/s
(b) 1/s
(c) 1/(M.s)
(d) 1/(M^2 .s)
6. The conjugate base of ammonium chloride is :
(a) NH3
(b) HNO2
(c) HCl
(d) HNO3
7. Which of the following is a weak acid?
(a) NH3
(b) HClO
(c) HCl
(d) HNO3
(27%, 3 points per question)
8. Calculate △S for the reaction:
2SO2(g) + O2(g)→2SO3(g)
S in J/mol K for SO2(g)= 248.1, SO3()256.6, O2(g)= 205.0
(a) -537 J/mol K
(b) +145 J/mol K
(c) -188 J/mol K
(d) +547 J/mol K
9. The production of nitric oxide is governed by the reaction:
4NH3(g) + 5O2(g)→ 4NO(g) + 6H2O(g)
If the rate at which oxygen is consumed is 8.29x10^-3 mol/L.s ,
what rate is NO produced?
(a) 8.29x10^-3 mol/L.s
(b) 1.04x10^-2 mol/L.s
(c) 6.63x10^-3 mol/L.s
(d) 5.53x10^-3 mol/L.s
10. The decompositon of hydrogen peroxide (H2O2) into O2(g) and liquid H2O
produced the following data:
time(min) 10.0 20.0 30.0 40.0 60.0
O2 volume(ml) 67.2 147 304 628 2769
What is the average rate of the reaction at 35.0 minute?
(a) 6.72 mL/min
(b) 10.1 mL/min
(c) 7.98 mL/min
(d) 15.7 mL/min
11. If the decomposition of reaction A folllows first-order kinetics, what
concentration of A remains if : [A]0 =0.273 M , k=1.53x10^-2 min^-1 ,
and the elapsed time = 1.61h
(a) 0.009M
(b) 0.0623M
(c) 0.197M
(d) 0.0273M
12. What is the molar solubility of CaF2 (Ksp=3.9x10^-11)?
(a) 6.24x10^-6 M
(b) 4.41x10^-6 M
(c) 2.14x10^-4 M
(d) 9.27x10^-5 M
13. What is the pH of a 0.150 M NaOH solutinon ?
(a) 0.82
(b) 3.05
(c) 11.66
(d) 13.18
14. Which species listed below is present in greatest concentration in 1.0 M
solution of NH4NO3 ? (Kb of NH3 = 1.8^10-5)
(a) NH4+
(b) NO3-
(c) OH-
(d) NH3
15. The synthesis of the pesticide thionyl chloride (OSCl2) proceeds according
to: SO3(g) + SCl2(l) ←→ OSCl2(l) + SO2(g)
If △G =106 kJ/mol for this reaction at 298k , what is the Keq at this
temperature? (R=8.314J/mol.K)
(a) 7.21x10^12
(b) 3.50x10^14
(c) 3.81x10^18
(d) 1.19x10^20
16. From the values given for △H and △S at 298K, which of the following
reactions is spontaneous under standard conditions at 298K?
(a) 2POCl3(g) → 2PCl3(g) + O2(g) △H=572kJ and △S=179J/K
(b) N2(g) + 3F2(g) → 2NF3(g) △H=-249kJ and △S=-278J/K
(c) N2(g) + 3Cl2(g) → 2NCl3(g) △H=460kJ and △S=-275J/K
(d) N2F4(g) → 2NF2(g) △H=85kJ and △S= 198J/K
Problems:
17. Briefly explain the three laws of thermodynamics, and give one
representative equation for each of them: (9%)
18. A reference book lists the following values for gallium at 298k
_______________________________________________________________
Substance △Hf(kJ/mol) △Gf(kJ/mol) S(J/mol K)
_______________________________________________________________
Ga(s) 0 0 x
Ga(l) 5.578 0.0888 59.25
Ga(g) 271.96 233.76 169.03
_______________________________________________________________
(a) Estimate the normal boiling point of gallium (4%)
(b) Gallium metal has a melting point of 29.8。C.
Estimate the S value of Ga(s) (4%)
19. The equilibrium constant for
NH4HS(s)←→NH3(g) + H2S(g)
at 25。C is Kc=1.6x10^-4
(a) What is the Kp value at this temperature? (4%)
(b) When solid NH4HS and 0.450 mol of gaseous NH3 were placed into a 2.0L
vessel at 25。C, what are the partial pressures of NH3 and H2S at
equilibrium? (4%)
(c) The van't Hoff equation shows the relationship between the equilibrium
constant and the absolute temperature:
ln(K1/K2) = -(△Hvap/R)(1/T1 - 1/T2)
Knowing that Kc is 2.96x10^-4 at 40。C , estimate the enthapy of this
reaction. (3%)
20. Consider an aqueous solution that contains 0.015M in Cd2+ ion and 0.020M
in Zn2+ ion. In order to seperate them by precipitating one of them as
sulfide without precipitating the other, what should be the pH value of
the saturated H2S ([H2S]=0.10M) solution? Show your calculation to
justify your answer.
(Ksp of CdS = 3.6x10^-29) (Ksp of ZnS = 1.1x10^-21)
(Ka1 and Ka2 of H2S = 1.1x10^-7 and 1.1x10^-19, respectively) (10%)
21. The decompositon of dimethy1 ehter at 504。C is a first-order reaction
with a half-life of 27.2 min.
(CH3)2O(g) → CH4(g0 + H2(g) + CO(g)
(a) What will be the partial pressure of (CH3)2O(g) after 1.50h if its initial
pressure was 650mmHg? (5%)
(b) What will be the total gas pressure after 1.50h ? (2%)
22. The following mechanism has been proposed for the reaction for the
reaction chlorine and dichloromethane, CH2Cl2:
Step 1. Cl2←→2Cl (forward and its reverse both fast)
Step 2. CH2Cl2 + Cl → CHCl2 + HCl (slow)
Step 3. CHCl2 + Cl → CHCl3 (fast)
(a) What is the overall reaction equation ? (2%)
(b) Indicate the intermediate species. (2%)
(c) Write the rate law implied by this mechnism, and show your assumption. (6%)
23. Consider the titration of 25.0mL of 0.100 M CH3COOH with 0.100M NaOH
solution (Ka of CH3COOH = 1.80x10^-5)
(a) Calculate the pH values after the following volumes of NaOH have been
added: 0mL ; 5mL; 10mL before the equivalence point ;
at equivalence point; 5.0mL after the equivalence point;
and 10mL after the equivalent point. (18%)
(b) Draw the titration curve (4%)
(c) What is the pKa range of the indicator which will be needed? (2%)
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