Tuesday, 10:45AM FORM A November 8, PRINT your name on this page and on your computer answer sheet.

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1 Name Chemistry ( ) Bubble on your scan sheet the EXAM II Form Code below: Tuesday, 10:45AM FORM A November 8, Instructions: 1. Each student is responsible for following instructions. Read this page carefully. 2. PRINT your name on this page and on your computer answer sheet. 3. CODE your name (LAST NAME FIRST) on the computer answer sheet using an ordinary (No. 2) pencil. It is very important to code the information correctly!! 4. Put all calculations on the examination pages. Do not make any extra marks on the computer answer sheet!! 5. This exam consists of 43 multiple-choice questions. Questions 1-8 are worth 3 points each. Questions 9-43 are worth 6 points each. For each question, choose the ONE best or correct answer and write it both on your exam paper and on the computer answer sheet. The computer answer sheet is the only one that will be graded! 6. This exam booklet consists of 9 pages (including this one), two Periodic Tables, a Formula/Data Sheet, a table of bond enthalpies, a table of enthalpies of formation, and a sheet of blank paper. Please check to be sure that you have them all! KEEP YOUR EXAM BOOKLET AND ANSWER SEET COVERED TO PROTECT TE INTEGRITY OF YOUR WORK!

2 Questions 1-4 pertain to the following: (a) C (b) N (c) O (d) Si (e) P On your scan sheet, bubble the letter for the atom that: 1. has the most metallic character. 2. has the largest first ionization energy. 3. has the largest atomic radius. 4. should have the most negative electron affinity Which of the following has the smallest radius? (a) Te 2 (b) I (c) Cs + (d) Ba 2+ (e) La 3+ Which of the following lists the species in order from largest to smallest radius? (a) Co, Co 2+, Co 3+ (b) Co, Co 3+, Co 2+ (c) Co 3+, Co 2+, Co (d) Co 3+, Co, Co 2+ (e) Co 2+, Co 3+, Co ow many unpaired electrons are there in a neutral ground-state 43 Tc atom? (a) 0 (b) 1 (c) 2 (d) 5 (e) 7 The ground state electron configuration of the technetium (III) ion ( 43 Tc 3+ ) is: (a) [Kr]5s 2 4d 4 (b) [Kr]5s 2 5p 4 (c) [Kr]4d 4 (d) [Kr]5s 2 4d 2 (e) [Kr]5p 4 It was observed that photons striking a clean metal surface would eject electrons from the metal only if the photons were of light of a minimum frequency. This phenomenon is called: (a) electroplating. (b) reverse osmosis. (c) mass spectrometry. (d) radioactive decay. (e) photoelectric effect. CEM 151 Exam II 2

3 When an atom has at least one electron in a higher energy level than the lowest possible, it is: (a) quantum leaping. (b) gettin jiggy wit it. (c) in the ground state. (d) in an excited state. (e) uncertain. Which species is/are paramagnetic? (a) Ca (b) Ca 2+ (c) both Ca 2+ and Ca (d) neither Ca 2+ nor Ca A sample of K 2 O is dissolved in water. The resulting solution would be: (a) basic (b) neutral (c) acidic (d) It is impossible to tell without additional information Which of the following equations corresponds to the fourth ionization energy of arsenic (As)? (a) As 4+ (g) As 5+ (g) + e (b) As (g) + 4 e As 4 (g) (c) As 2+ (g) As 3+ (g) + e (d) As 3+ (g) As 4+ (g) + e (e) As (g) Zn (g) + 3 e Which of the following equations corresponds to the electron affinity of selenium (Se)? (a) Se + (g) + e Se (g) (b) Se (g) + e Br (g) (c) Se (g) Se + (g) + e (d) Se (g) Se (g) + e (e) Se (g) + e Se (g) WMVX Mix broadcasts its signal at a frequency of Mz. What is the wavelength of WMVX s signal? (a) m (b) 2.82 m (c) m (d) m (e) m Referring to the previous Question, what is the smallest amount of energy that an object can absorb from WMVX s signal? (a) less than J (b) between J and J (c) between J and J (d) between J and J (e) more than J CEM 151 Exam II 3

4 Which of the following statements about Bohr s model of the atom is FALSE? (a) It could explain the observed line emission spectra of hydrogen. (b) It could explain the observed line spectra of one-electron species such as e + and Li 2+. (c) It could explain electronic structure of many-electron atoms. (d) It required only one quantum number to describe electron orbits. (e) It modeled the atom like a solar system, with the nucleus in the center and the electrons orbiting like planets. Which of the following statements is TRUE? (a) A baseball moving at 55 mph has observable wave properties. (b) A baseball moving at 55 mph has wave properties that are so small as to be insignificant. (c) An electron in motion at typical speeds in an atom has no wave properties. (d) An electron in motion at typical speeds in an atom has wave properties that are so small as to be insignificant. (e) None of these are true. A certain third-period element has the following successive ionization energies: IE 1 = 1012 kj/mol, IE 2 = 1900 kj/mol, IE 3 = 2910 kj/mol, IE 4 = 4960 kj/mol, IE 5 = 6270 kj/mol, IE 6 = 22,200 kj/mol. This element must be: (a) Mg (b) Al (c) Si (d) P (e) S The ground state electron configuration of the titanium ( 22 Ti) atom is: (a) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 4d 2 (b) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4 (c) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 4p 2 (d) 1s 2 2s 2 2p 6 3s 2 3p 6 4d 4 (e) 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 2 Which of the following statements about the following reaction at 298 K is/are true? (Note that graphite is the most stable form of carbon at standard conditions.) C (s, graphite) + O 2 (g) CO 2 (g) I. The enthalpy of this reaction equals the heat of combustion of graphite. II. The enthalpy of this reaction equals the heat of formation of carbon dioxide. III. This is a combustion reaction. IV. This is a redox reaction. (a) I and III only. (b) II and IV only. (c) I, III, and IV only. (d) I, II, III, and IV. (e) I, II, and IV only. CEM 151 Exam II 4

5 Consider the following reaction: KClO 3 (s) KCl (s) + 3/2 O 2 (g) Δ = 44.7 kj Calculate Δ for the decomposition of 15.2 grams of KClO 3 to form KCl and O 2. (a) kj (b) kj (c) 5.54 kj (d) 11.1 kj (e) 679 kj Use bond enthalpies (on data sheet) to estimate Δ for the following reaction: C C + C N C C C N (a) 347 kj (b) 80 kj (c) + 80 kj (d) kj (e) kj The enthalpy change for the reaction between tungsten (W) and graphite is difficult to measure directly because the reaction occurs at 1400 o C: W (s) + C (s, graphite) WC (s) owever, the heats of reactions of the elements and of tungsten carbide with oxygen can be measured and are given below: 2 W (s) + 3 O 2 (g) 2 WO 3 (s) Δ = kj C (s, graphite) + O 2 (g) CO 2 (g) Δ = kj 2 WC (s) + 5 O 2 (g) 2 WO 3 (s) + 2 CO 2 (g) Δ = kj The enthalpy of reaction, Δ, for the formation of tungsten carbide, WC (s), from its elements is: (a) 3.8 kj (b) 38.0 kj (c) kj (d) kj (e) none of these The change in enthalpy for a chemical reaction results primarily from a difference in: (a) the volume occupied by the reactants versus the volume occupied by the products. (b) the number of atoms in the reactants versus the number of atoms in the products. (c) the amount of heat contained in the reactants versus the amount of heat contained in the products. (d) the strengths of the chemical bonds in reactants versus the strengths of the chemical bonds in the products. (e) None of these. CEM 151 Exam II 5

6 A certain process absorbs 50 kj of heat while doing 25 kj of work on the surroundings. What is ΔE SYS for this process? (a) 75 kj (b) 25 kj (c) +25 kj (d) +75 kj (e) none of these The combustion of acetylene (C 2 2 ) is a reaction commonly used in welding torches. Using enthalpies of formation, calculate the enthalpy of this reaction. 2 C 2 2 (g) + 5 O 2 (g) 4 CO 2 (g) O (g) (a) 2599 kj (b) 2511 kj (c) 862 kj (d) kj (e) kj Which of the following is FALSE? (a) Enthalpy (Δ) is a state function. (b) Volume (V) is a state function. (c) Pressure (P) is a state function. (d) Indiana (IN) is a state. (e) eat (q) is a state function. Which of the following correctly represents a neutral ground-state electron configuration of Rh? (a) [Kr] 5s 4d 5p. (b) [Kr] 5s 4d 5p. (c) [Kr] 5s 4d 5p. (d) [Kr] 5s 4d 5p. (e) [Kr] 5s 4d 5p. 30. The above diagrams from (left to right) represent what types of orbitals? (a) s, p, and d orbitals, respectively. (b) p, s, and d orbitals, respectively. (c) d, s, and p orbitals, respectively. (d) p, d, and s orbitals, respectively. (e) d, p, and s orbitals, respectively. CEM 151 Exam II 6

7 In lecture, you observed a demonstration of an endothermic reaction involving two solids reacting to produce water, gaseous ammonia, and other aqueous products, with the reaction beaker being frozen to a wet cafeteria tray. What was our sure indication that the reaction was endothermic? (a) The reaction produced a gas. (b) Two solid reactants produced an aqueous product. (c) The reaction products were very cold. (d) All reactions that proceed readily are endothermic. (e) None of the above. Consider the two waves of equal speed shown below. Which statement about the waves is true? 33. Wave No. 1 Wave No. 2 (a) Wave No. 1 has the same wavelength and the same frequency as Wave No. 2. (b) Wave No. 1 has twice the wavelength and twice the frequency of Wave No. 2. (c) Wave No. 1 has half the wavelength and twice the frequency of Wave No. 2. (d) Wave No. 1 has twice the wavelength and half the frequency of Wave No. 2. (e) None of the above are true. Which of the following is the set of quantum numbers for the highest-energy electron in Rb? n l m l m s (a) ½ (b) ½ (c) ½ (d) ½ (e) None of these Zippy uses 30 gallons of gaseous propane (C 3 8 ) at a tailgate party. What volume of CO 2 gas, measured at the same temperature and pressure, is produced? C 3 8 (g) + 5 O 2 (g) 3 CO 2 (g) O (g) (a) 30 gallons. (b) 150 gallons. (c) 90 gallons. (d) 120 gallons. (e) none of these. Which of the following gases is the least dense at 28 o C and 782 torr? (a) carbon monoxide. (b) sulfur dioxide. (c) sulfur hexafluoride. (d) hydrogen iodide. (e) xenon. CEM 151 Exam II 7

8 What volume would be occupied by a 79.9-gram sample of argon gas at STP? (a) 2.00 L (b) 22.4 L (c) 44.8 L (d) 39.9 L (e) 120. L Which statement(s) about the van der Waals equation (below) are true? 2 n a P + 2 ( V n b) = nrt V I. The term added to P accounts for intermolecular attractions. II. The term subtracted from V accounts for space occupied by molecules. III. The constants a and b would be zero for an ideal gas. (a) I and II only. (b) III only. (c) I, II, and III. (d) II and III only. (e) none of these. Consider two one-liter flasks: one contains F 2 gas at STP and the other contains propane gas (C 3 8 ) at STP. Which of the following quantities would be different for the two flasks? I. density II. number of molecules III. average kinetic energy of molecules (a) I only. (b) II only. (c) III only. (d) I and II only. (e) II and III only. What would happen to the volume of a sample of an ideal gas if the absolute temperature were halved at constant pressure? (a) the volume would double. (b) the volume would be halved. (c) the volume would be squared. (d) the volume would stay the same. (e) the gas would not allow you to do this. Before I go out huffing and puffing on my mountain bike, I inflate my tires with air at 15 o C to a total pressure of 80 pounds per square inch (psi). After returning home and collapsing, the temperature of the air inside my tires has reached 30 o C. Assuming the volume of the tire did not change, what is the pressure of the air inside the tire? (a) 40 psi. (b) 76 psi. (c) 80 psi. (d) 84 psi. (e) 160 psi. CEM 151 Exam II 8

9 41. Which of the following gases has particles with the fastest average speed at 28 o C? (a) carbon dioxide. (b) sulfur trioxide. (c) sulfur hexafluoride. (d) hydrogen chloride. (e) helium. 42. The graph below shows the distribution of molecular speeds of argon and helium at the same temperature. 43. Which curve describes the behavior of argon? (a) Curve 1 (b) Curve 2 (c) It is impossible to tell without additional information. Zr 2+ and Sr are isoelectronic. (a) True (b) False END OF EXAM Check to see that you have entered 43 answers on your scan sheet. Proofread your work. You may take this test booklet with you but you must return your scan sheet before leaving the room! Answers will be posted on the course web site tonight or tomorrow. CEM 151 Exam II 9