(3 pts) 2. In which gas sample do the molecules have a lower average kinetic energy? (A) Gas A (B) Gas B (C) Neither

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1 Consider two samples of gas, A and B, as shown in the figure below. Both containers are at the same temperature and pressure. Gas A 1.0 L 0.32 g Gas B 1.0 L 0.48 g (3 pts) 1. Which gas sample contains more molecules? (A) Gas A (B) Gas B (C) Neither (3 pts) 2. In which gas sample do the molecules have a lower average kinetic energy? (A) Gas A (B) Gas B (C) Neither (3 pts) 3. In which gas sample do the molecules have a lower average speed? (A) Gas A (B) Gas B (C) Neither (3 pts) 4. The amount of energy required to remove an electron from a neutral atom, producing a cation, is called the atom s. (A) ionization energy (B) electron affinity (C) polarizability (D) electronegativity (E) magnetic moment (3 pts) 5. An atom s ability to attract the shared electrons in a chemical bond is known as the atom s. (A) electron affinity (B) ionization energy (C) polarizability (D) electron configuration (E) electronegativity (3 pts) 6. Any atom or ion whose electron configuration contains one or more unpaired electrons is said to be. (A) excited (B) paramagnetic (C) radioactive (D) unstable (E) diamagnetic B L.S. Brown

2 NAME: (A) (B) (C) (D) (E) For questions 7 9, consider the five graphs sketched above. The descriptions of the possible plots are given below as y vs. x. For each question choose the graph that best represents the relationship described, and use the letters labelling the graphs as the answer choices. (3 pts) 7. Which graph represents a plot of PV vs. T for an ideal gas at constant n? A (3 pts) 8. Which graph represents a plot of density vs. T for an ideal gas at constant P? D (3 pts) 9. Which graph represents a plot of PV vs. P for 1.0 mole of an ideal gas at constant T? E For questions 10 12, consider a bromine atom (Br, Z = 35) in its ground state electron configuration. (3 pts) 10. How many of the bromine atom s electrons will have n = 3 as one of their quantum numbers? (A) 3 (B) 6 (C) 8 (D) 15 (E) 18 (3 pts) 11. How many of the bromine atom s electrons will have l = 1 as one of their quantum numbers? (A) 17 (B) 10 (C) 8 (D) 5 (E) 12 (3 pts) 12. Which of the following sets of quantum numbers could describe an electron in the bromine atom s highest occupied energy level? (A) n = 3, l = 1, m l = 0, ms = +½ (B) n = 4, l = 2, m l = 1, ms = ½ (C) n = 4, l = 1, m l = 1, ms = +½ (D) n = 3, l = 2, m l = 0, ms = 0 (E) n = 4, l = 2, m l = 1, ms = L.S. Brown B3

3 (3 pts) 13. Which atom or ion should have the smallest radius? (A) Ar (B) Ca 2+ (C) Ca (D) Ga (E) Cl (3 pts) 14. Which atom or ion should have the smallest ionization energy? (A) K + (B) S (C) P (D) P 3 (E) Ar (3 pts) 15. Of the 5 ions or atoms listed above in #14, how many are paramagnetic in their ground state electron configurations? (A) 4 (B) 3 (C) 2 (D) 1 (E) 0 (3 pts) 16. Which of the following chemical bonds would be the most polar? (A) C Cl (B) H Cl (C) Cl Cl (D) Si Cl (E) P Cl (3 pts) 17. A neutral atom in its ground state has the following electron configuration: [Kr] 5s 2, 4d 10, 5p 4. What element is it? (A) Te (B) Ge (C) Se (D) I (E) Sn (3 pts) 18. A neutral atom in an excited state has the following electron configuration: 1s 2, 2s 2, 2p 6, 3s 2, 3p 4, 4s 1. What element is it? (A) K (B) S (C) Cl (D) Ar (E) O (3 pts) 19. An ion with a 2 charge has the following electron configuration: 1s 2, 2s 2, 2p 6, 3s 2, 3p 6. What element is it? (A) P (B) S (C) Cl (D) Ar (E) Ca B L.S. Brown

4 NAME: (4 pts) 20. The figure below shows the photoelectron spectrum for aluminum, plotted like the spectra we looked at in class. The numbers give the binding energies for the different peaks. How much energy is required to remove an electron from the 3s subshell of an aluminum atom? (A) 151 MJ/mol (B) 12.1 MJ/mol (C) 7.19 MJ/mol (D) 1.09 MJ/mol (E) 0.58 MJ/mol (5 pts) 21. The graph below shows the first three ionization energies for sodium, magnesium, and aluminum. (The X, Y, and Z labels are used below to identify the different lines.) Ionization energy (kj/mol) X Y Z Number of electrons removed Which of the following choices correctly matches the three data sets in the graph to the three elements? (A) X = Al, Y = Mg, Z = Na (C) X = Mg, Y = Na, Z = Al (B) X = Na, Y = Al, Z = Mg (D) X = Al, Y = Na, Z = Mg (E) X = Na, Y = Mg, Z = Al 2018 L.S. Brown B5

5 (6 pts) 22. A sealed bulb containing neon gas had a pressure of 543 torr at 20.0 C. When the temperature was increased, the pressure rose to 782 torr. What was the final temperature? (A) 97 C (B) 149 C (C) 112 C (D) 29 C (E) 205 C P 1 = P 2, so T T 1 T 2 = P 2 T 2 P 1 = torr 293 K=422 K= torr (6 pts) 23. What is the frequency of red light with a wavelength of 655 nm? (A) Hz (C) Hz (B) Hz (D) Hz (E) Hz c=λν, so ν= c λ = m/s m = s 1 B L.S. Brown

6 NAME: (10 pts) 24. The ionization energy of a particular element is 1086 kj/mol. Suppose an atom of this element has already absorbed a photon with a wavelength of 245 nm so that it has been promoted to an excited state. What would be the longest wavelength of light that would be able to provide enough energy to eject an electron from the excited atom? (This is very similar to a homework problem from Set #5. It may help you to try to draw an energy level diagram summarizing the process.) First convert the IE from kj/mol to J/atom: ion Ex. state Get energy of the 245 nm photon, then subtract that from the IE. Gr. state J J = J J J = J (actually J if we do the sig figs right, but don t take off for that) 2018 L.S. Brown B7

7 (10 pts) 25. When a photoelectric effect experiment was carried out using silver metal and light at frequency n, electrons were emitted with a kinetic energy of J. The frequency was increased to 2n and the experiment was repeated, still using the same silver target. This time electrons were emitted with a kinetic energy of J. Find the electron binding energy for silver. (The actual frequencies used were not recorded, but it is still possible to find the binding energy. One way to start is to realize that the difference in the 2 KE s is the smaller photon E. But I think it is likely that more people will start with the energy equation for the PE effect, and then write 2 versions: Ephoton = BE + KE hn = BE J (for the 1 st experiment) 2hn = BE J (for the 2 nd experiment) The 2 BE s are the same. Subtract the 1 st eq from the 2 nd to get: hn = J Put that back into either equation above to find BE. I will do the 1 st one. hn = J = BE J And BE = J B L.S. Brown

8 NAME: (12 pts) 26. The first step in the production of nitric acid involves the reaction of NH3 and O2 to produce NO and H2O. 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) Suppose this reaction is carried out in the apparatus shown below. When the valve separating the bulbs is opened, the gases mix and the reaction goes to completion. Assume that the final volume is 3.00 L and the temperature is constant throughout the process L O atm 1.00 L NH atm Calculate the partial pressure of each of the gases that will be present when the reaction is completed. (HINT: As long as all 4 substances are gases, the result does not depend on the temperature.) T is constant, so n is proportional to PV. So I am going to work this out using L atm in place of moles I did a problem like this in class, and I hope a number of them will realize that is the easiest way. It also works if you pick a T as long as you use the same T throughout. At the start, we have 1.00 L atm of O2 and 1.50 L atm of NH3. Comapring with the 5:4 ratio in the reaction, we can see that the O2 will be the LR. That means at the end we will have products (NO and H2O) present along with left over NH3. 1 L atm O 2 4 mol NO 5 mol O 2 = L atm NO 1 L atm O 2 6 mol H 2O 5 mol O 2 = 1. 2 L atm H 2 O 1 L atm NH 3 4 mol NH 3 5 mol O 2 = 0. 8 L atm NH 3 react, so = 0. 7 L atm left Divide all those L atm numbers by 3 L total V to get partial P s: 0. 8 L atm P NO = = atm = 203 torr 3 L 1. 2 L atm P H2 O = = atm = 304 torr 3 L 0. 7 L atm P NH3 = = atm = 177 torr 3 L 2018 L.S. Brown B9