18. The average mass of a carbon atom is 12.011. Assuming you were able to pick up only one carbon unit, the chances that you would randomly get one with a mass of 12.011 is ___________.
(A) 0%
(B) 0.011%
(C) about 12%
(D) 12.011%
(E) greater than 50%

49 Which of the following is one of the challenges engineers and workers had to face during the construction of the Qinghai-Tibet Railroad? (A) Travelers from Beijing may suffer altitude sickness in Lhasa. (B) The idea of a train trip is not as appealing as that of air travel. (C) The tourism industry is impossible on the snow-covered permafrost. (D) The railroad track may become bent or curved if frozen ground melts.

50 Which of the following statements can be inferred from this passage? (A) The Qinghai-Tibet Railroad is a record holder in terms of the total length of its track. (B) The completion of the Qinghai-Tibet Railroad is likely to enhance Tibet's tourism industry. (C) Thousands of engineers died of altitude sickness while building the Qinghai-Tibet Railroad. (D) The permafrost under the Qinghai-Tibet Railroad makes it necessary to breathe bottled oxygen.

16. Select the answer with the correct number of decimal places for the following sum: 13.914 cm + 243.1 cm + 12.00460 cm = (A) 269.01860 cm (B) 269.0186 cm (C) 269.019 cm (D) 269.02 cm (E) 269.0 cm

17. The difference between a student's experimental measurement of the density of sodium chloride and the known density of this compound reflects the ___________ of the student's result. (A) accuracy (B) precision (C) random error (D) systematic error (E) indeterminate error

19. A catalyst ___________. (A) changes the enthalpy of the reaction (B) does not change the activation energy (C) provides an alternate pathway to the reaction (D) does not change the effective collisions (E) is consumed when more reacting molecules are added

20. For a gas sample, which conditions of P (pressure), T (temperature), and n (molar number), respectively, are most ideal? (A) high P, high T, high n (B) low P, low T, low n (C) high P, low T, high n (D) low P, high T, high n (E) low P, high T, low n

複選題21. One mole of an ideal gas at 20 °C is expanded isothermally and reversibly from 100 L to 200 L. Which statement is correct? (A)△ Sgas = 0 (B) △ Ssurr = 0 (C) △ Suniv = 0 (D) △ Sgas = Rln2 (E) △ Sgas = △Ssurr

22. Which of the following ionic compounds has the largest lattice energy? (A) LiF (B) NaCl (C) MgO (D) KBr (E) BaCl2

23. Which of the following species has a trigonal bipyramid structure? (A) IF5 (B) I3− (C) NH3 (D) PCl5 (E) All of the above.

24. Naturally occurring copper exists in two isotopic forms: 63Cu and 65Cu. The atomic mass of copper is 63.55 amu. What is the approximate natural abundance of 63Cu? (A) 70% (B) 63% (C) 90% (D) 50% (E) 30%