CHEM 101 WINTER 08-09 EXAM II On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. Avogadro’s Number: 6.022 × 1023 mol-1 Speed of Light: c = 3.00 x 108 mys-1 Planck’s Constant: h = 6.626 x 10-34 Jys Rydberg Constant: R = 2.179 x 10-18 J E = hc/λ = hυ q = m c ΔT 1 cal = 4.184 J 1. Please choose the letter “a” as your answer for this question. 2. Which statement about energy is false? a. Chemical reactions are processes that transfer energy. b. Thermodynamics is the science of working and heating processes. c. The chemical energy of foods and fuels is a type of potential energy. d. Working and heating are processes that transfer energy. e. The thermal energy of nanoscale objects is a type of potential energy. 3. Determine the incorrect relationship given below. a. 80.0 cal/g = 312 J/g b. 1 μJ = 1 × 10−6 J c. 1000 cal = 1 kcal d. 1000 J = 1 kJ e. 44.0 kJ = 1.05 × 104 cal 4. The First Law of Thermodynamics states that: a. The total energy of the universe is constant. b. The total entropy of the universe is increasing. c. Molecules move faster as temperature increases. d. Samples with different temperatures that come in contact with one another will reach thermal equilibrium. e. Energy transfers from hotter objects to cooler objects. 5. If heat is transferred from the system to the surroundings then a. qsystem and qsurroundings are both negative b. qsystem is positive and qsurroundings is negative c. qsystem = qsurroundings = 0 d. qsystem is negative and qsurroundings is positive e. qsystem and qsurroundings are both positive

6. Heating a 25.0 g sample of each substance below with 375 J of energy will cause which substance to have the smallest increase in temperature? a. water (specific heat = 4.184 J g−1 °C−1) b. iron (specific heat = 0.451 J g−1 °C−1) c. gold (specific heat = 0.128 J g−1 °C−1) d. copper (specific heat = 0.385 J g−1 °C−1) e. Not enough information to determine. 7. A 20.0 g sample of aluminum (specific heat = 0.902 J g−1 °C−1) with an initial temperature of 48.6°C is heated with 427 J of energy. What is the final temperature of the sample? a. 76.8°C b. 26.2°C c. 72.3°C d. 23.7°C e. 24.9°C 8. What is the molar heat capacity of magnesium difluoride, MgF2 (specific heat = 1.00 J g−1 °C−1)? a. 245 J mol−1 °C−1 b. 62.3 J mol−1 °C−1 c. 117 J mol−1 °C−1 d. 43.3 J mol−1 °C−1 e. 5.30 × 1022 J mol−1 °C−1 9. Determine the quantity of ice required to absorb exactly 50 kJ of energy when the ice warms from −50.0°C to −10.0°C (specific heat of ice = 2.06 J g−1 °C−1). a. 0.485 g b. 607 g c. 2.43 × 103 g d. 485 g e. 0.607 g 10. Which process is exothermic? a. warming milk b. subliming dry ice c. evaporating alcohol d. freezing rain drops e. defrosting frozen food 11. Based on the following thermochemical equation, which statement is false? NH3 (l) NH3 (g) H° = +23.4 kJ a. b. c. d. e.

The internal energy of the surroundings increases. The enthalpy change for the gas condensing into a liquid is known. The enthalpy change is endothermic. The atmospheric pressure for the process is known. The thermochemical equation represents a physical change.

12. What is the enthalpy change when 32.0 g of CH4 are burned in excess O2? CH4(g) + 2O2(g) CO2(g) + 2H2O(l) H°= −890 kJ a. b. c. d. e.

−1780 kJ −890 kJ −445 kJ +890 kJ +1780 kJ

13. The complete combustion of 1.47 g of methanol produces 29.3 kJ of heat. Determine the the reaction and its sign. CH3OH(l) + 3/2O2(g) CO2(g) + 2H2O(g) a. +638 kJ b. −1.35 kJ c. −638 kJ d. +938 kJ e. −938 kJ

H° for

14. Which of the following statements is false? a. Breaking weak bonds and making a greater number of equally weak bonds is endothermic. b. Breaking weak bonds and making an equal number of strong bonds is exothermic. c. Bond enthalpy values are based on molecules in the gas phase. d. Bond enthalpies quantify the energy change for the complete separation of two bonded atoms in a molecule at constant pressure. e. Breaking bonds is always endothermic. 15. Which statement regarding an orbital is false? a. An orbital describes the location of the electron 90% of the time. b. An electron shell consists of a collection of orbitals with the same principal quantum number. c. Only one electron is allowed per orbital. d. An orbital is three dimensional. e. An orbital may be designated with the letters s, p, d, f. 16. Which word or phrase least applies to the quantum number represented by the symbol n? a. principal b. shell c. distance from nucleus d. size e. shape 17. Which statement is true? a. Two electrons in the 1s orbital will have the same spin at the ground state. b. The 3d orbitals have lower energy than the 2p orbitals. c. The p orbitals occur in groups of 5. d. The 2p orbitals hold up to 6 electrons. e. The 4p orbitals hold more electrons than the 3d orbitals.

18. Which set of quantum numbers is not allowed? a. n = 4, l = 3, ml = 0, ms = −1/2 b. n = 2, l = 1, ml = 1, ms = +1/2 c. n = 1, l = 0, ml = 0, ms = +1/2 d. n = 0, l = 0, ml = 0, ms = +1/2 e. n = 3, l = 1, ml = 0, ms = +1/2 19. What is the correct ground state electron configuration for aluminum? a. 1s22s22p43s23p3 b. 1s22s22p23s23p23d24s1 c. 1s22s1 d. 1s22s22p23s23p24s25s1 e. 1s22s22p63s23p1 20. Which element has the following ground state electron configuration? 1s22s22p63s23p63d104s24p65s2 a. Pd b. In c. Sr d. Ni e. Fe 21. Which of the following electron configurations is for an atom in an excited state? a. 1s22s22p63s23p6 b. 1s22s22p63s23p5 c. [Kr]5s2 d. 1s22s22p6 e. 1s22s22p63s23p54s1 22. What is the electron configuration of O2-? a. 1s22s22p2 b. 1s22s22p4 c. 1s22s22p1 d. 1s22s22p5 e. 1s22s22p6 23. Which one of the following does not have the electron configuration [Ne]3s23p6? a. K+ b. Ca2+ c. Br− d. Cl− e. Ar 24. Atoms or ions with unpaired electrons are attracted to a magnetic field and are called: a. diamagnetic. b. paramagnetic. c. lanthanides. d. ferromagnetic. e. isoelectronic.

25. Which of these elements has the smallest first ionization energy? a. Be b. Sr c. Ca d. Mg e. Cs 26. Which of these elements has an electron affinity greater than zero? a. Br b. Te c. As d. I e. Kr