Chem 222
Exam 1
January 9, 2015
Name ________________
SHOW YOUR WORK. NO WORK, NO CREDIT
INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS
Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.
On my honor, I pledge that I have upheld the Honor Code, and that the work I have done on this assignment has been
honest, and that the work of others in this class has, to the best of my knowledge, been honest as well.
Signed _________________________________________________________________
If you feel you can’t sign this, contact the instructor (email, or in person)
Silver Group: Ag, Hg, Pb
Aluminum-Nickel Group: Ni, Fe, Co, Mn, Al, Cr, Zn
Copper-Arsenic Group: Cu, Hg, Pb, As, Sb, Bi, Sn, Cd
Barium-Magnesium Group: Na, K, Mg, Ca, Ba, NH4+1
Constants and Equations Supplied on Exams
Zeff s/p: same n = 0.35, n-1 = 0.85,  n-2 = 1.00
1
2
d/f: same n = 0.35, rest = 1.00
1
particles
mole
m
J
L·atm
h = 6.626 x 1034 J·s c = 2.998 x 108
R = 8.314
= 0.08206
s
K·mole
K·mole
C
C
J
Amp =
F = 96500
= 96500
J = C·V
s
mole
V·mole
RT
RT
0.05916
E = E° ln (Q)
= 0.025693 V at 25 °C E = E° log (Q)
nF
F
n
 = 2.828   
0 °C = 273.15 K
s =  n(n  2) 2
N A = 6.022 x 1023
Circle the correct answer. (multiple choice = 2 pts. Each)
1.
For an electron in a given atom, a larger n means a A) smaller average distance from the nucleus and a higher orbital energy. B) larger average distance from the nucleus and a higher orbital energy. C) smaller average distance from the nucleus and a lower orbital energy. D) larger average distance from the nucleus and a lower orbital energy.
2.
An electron in a 3d orbital can have a wave function with which set of quantum numbers, (n, l, ml, ms)? A) (4, 3, 0, 1/2) B) (3, 2, ‐3, –1/2) 3.
D) (3, 2, 0, 1/2) If two electrons are to be distributed among two molecular orbitals of the same energy, how would they be arranged? A) C) (3, 1, –1, –1/2) B) C) 1
D) 4.
How many radial nodes (spherical nodes) are there in a 4s orbital? A) four B) zero C) three D) two 5.
The probability density plot on the right is consistent with a A) 2s orbital. B) 2s or a 2pz orbital. C) 2pz orbital. D) 3s orbital. 6.
Which has the highest Z* for its valence electrons? A) K B) Na C) P D) Si 7.
For the fourth-shell orbital shown, what are the principal quantum number, n, and the azimuthal quantum number, l? A) n = 4, l = 2 B) n = 4, l = 3 C) n = 4, l = 1 D) n = 4, l = 0 8.
Arrange in order from the smallest to the largest bond angle: CH3+, NF3, NH4+, XeF4. A) NF3, NH4+, XeF4, CH3+
B) XeF4, NF3, NH4+, CH3+
C) CH3+, NF3, NH4+, XeF4 D) XeF4, NH4+, NF3, CH3+ 9.
Arrange the elements F, Be, O, N, and C in order of decreasing first ionization energy. a) F > O > N > C > Be c) F > N > O > C > Be b) Be > C > O > N > F d) Be > C > N > O > F 10. The in‐phase, side‐on overlap of a pair of 2p orbitals forms a ____ molecular orbital. A) 2p B)  2p * C) 2p D) 2p* 11. Which drawing represents a  bonding molecular orbital for a homonuclear diatomic molecule? A) B) C) D) 12. Which salt is insoluble in water? a) Sn(NO3)2 b) PbCrO4 c) Na2CO3 d) Cu(C2H3O2)2 13. Which reagent will distinguish between Ag+ (aq) and Hg2+2 (aq)? a) HNO3 (aq) b) NaCl (aq) c) NH3 (aq) 14. Which will distinguish between Sn+4 and Sn+2? a) color b) HgCl2 d) con HCl d) con NH3 2
d) Zn(NO3)2 (aq) 15. Will a precipitate form when equal volumes of 0.10 M Pb(NO3)2 and 0.10 M Na2S are mixed? If so, identify the precipitate. A. Yes, the precipitate is PbS. C. Yes, the precipitate is Na2S. 16. (2 pts) What is the name for SnS2? B. Yes, the precipitate is NaNO3. D. No, a precipitate will not form. ________________________________________ 17. (2 pts) What is the formula for sodium arsenate? ________________________________________ 18. (10 pts) Based on Slater’s rules, what is the effective nuclear charge felt by the last electron placed in the valence shell of arsenic? 19. (10 pts) Following the filling order set by the periodic table, Ni’s electron configuration is [Ar] 4s2 3d8. What is the total pairing energy, expressed as nc + me, for the electrons outside the Ar core in nickel? Show your reasoning. 20. (1 pt each part) Using the Lewis structure on the right for selenious acid, H2SeO3: a) Are all Se‐O bonds the same length? ___________________ b) What is the hybridization of the selenium atom? ___________________ c) What is the electron pair geometry around the selenium? ___________________ d) What is the molecular geometry (shape) around the Se? ___________________ e) What are the approximate O‐Se‐O bond angles (using < or >)? ___________________ f) Is the molecule polar or non‐polar? ___________________ 21. (10 pts) Given the following data for bond angles and bond lengths, explain in detail how electronegativity theory rationalizes the trend in bond angles. PCl3
PBr3
Molecular Formula
PF3
Bond Angle (°)
97.8
100.3
101.0
Bond Length (pm)
157
204
220
22. (10 pts) Draw the Lewis structure for the fluorosulfate ion, SO3F‐1; include any resonance structures that might exist. Then draw one structure that shows the 3‐dimensional shape using wedges and dashes. 23. (10 pts) A solution known to contain only cations of the silver group forms a white precipitate when treated with 6 M HCl. The precipitate is washed with cold water. When the precipitate is treated with 15 M ammonia, the precipitate remains completely unchanged, the only indication of a reaction being the formation of a slightly milky color in the ammonia. Indicate which ions of the silver group are present, absent, and undetermined. Clearly explain your reasoning (why it is there or why it is absent) and account for all observations made. 24. (10 pts) A copper‐arsenic group unknown was treated with the group reagent in the usual manner. A yellow precipitate was formed that was completely insoluble in excess ammonium sulfide. What ions in the copper‐
arsenic group are present, absent, and undetermined? Clearly explain your reasoning (why it is there or why it is absent) and account for all observations made. 3
Chem 222 Exam 2 Name ________________ January 16, 2015 SHOW YOUR WORK. NO WORK, NO CREDIT INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers. On my honor, I pledge that I have upheld the Honor Code, and that the work I have done on this assignment has been
honest, and that the work of others in this class has, to the best of my knowledge, been honest as well.
Signed _________________________________________________________________
If you feel you can’t sign this, contact the instructor (email, or in person)
Silver Group: Ag, Hg, Pb Aluminum‐Nickel Group: Ni, Fe, Co, Mn, Al, Cr, Zn Copper‐Arsenic Group: Cu, Hg, Pb, As, Sb, Bi, Sn, Cd Barium‐Magnesium Group: Na, K, Mg, Ca, Ba, NH4+1 Constants and Equations Supplied on Exams
Zeff s/p: same n = 0.35, n-1 = 0.85,  n-2 = 1.00
1
d/f: same n = 0.35, rest = 1.00
1
particles
mole
m
J
L·atm
h = 6.626 x 1034 J·s c = 2.998 x 108
R = 8.314
= 0.08206
s
K·mole
K·mole
C
C
J
Amp =
F = 96500
= 96500
J = C·V
s
mole
V·mole
RT
RT
0.05916
E = E° ln (Q)
= 0.025693 V at 25 °C E = E° log (Q)
nF
F
n
 = 2.828    2
0 °C = 273.15 K
s =  n(n  2) 2
N A = 6.022 x 1023
Circle the correct answer. (multiple choice = 2 pts each) 1. Which pair of atomic orbitals (oriented in the plane of the paper as shown) might form a  bond? A) B) C) D) 2.
Molecular orbitals extending over more than two atoms provide an explanation for A) resonance in the Lewis model. C) coordinate covalent bonding. B) ionic bonding. D) paramagnetism. 3.
4.
Which Br∅nsted‐Lowry acid has the strongest conjugate base? A) HF B) HNO3 C) HCl D) HClO4 Which of the following statements about molecular orbitals is false? 1
A) Degenerate molecular orbitals follow Hundʹs Rule. B) Because of the relative magnitude of the effect of MIXING, there is a slightly different molecular orbital diagram for Z < 8 and Z ≥ 8. C) s molecular orbitals are lower in energy than s *, at a given energy level. D) Antibonding molecular orbitals are never occupied with electrons. 5.
Which of the following statements regarding stable heteronuclear diatomic molecules is/are false? I. The bonding molecular orbitals have more character from the more electronegative element than of the less electronegative element. II. Their molecular orbital diagrams are more symmetrical than those of homonuclear diatomic molecules. III. The greater the difference in energy between two atomic orbitals, the more likely they are to overlap and form bonding and antibonding molecular orbitals. A) II only. B) Both I and II. C) Both II and III. D) III only. 6. Arrange the following 0.10 M aqueous solutions in order of increasing pH: NaOH, HBr, NaCH3CO2, KBr, NH4Br. A) NaOH, NaCH3CO2, NH4Br, KBr, HBr B) HBr, NH4Br, KBr, NaCH3CO2, NaOH C) NaOH, NaCH3CO2, KBr, NH4Br, HBr D) HBr, KBr, NH4Br, NaCH3CO2, NaOH 7. What is the strongest acid among the following? A) H2SeO4 B) H2SO3 C) H2SeO3 D) H2SO4 8. For Cu2+ and CO2, which will behave as a Lewis acid toward OH‐1 in water? A) only CO2 B) only Cu2+ c) Cu2+ and CO2 D) neither Cu2+ nor CO2 9. When 50 mL of 0.10 M NH4Cl is added to 50 mL of 0.10 M NH3, relative to the pH of the 0.10 M NH3 solution the pH of the resulting solution will A) decrease. B) increase. C) remain the same. D) become 7. 10. Which statement is true about superacids? A) They will dissolve most materials. B) They are species with a Hammett Ho parameter more negative than ‐12. C) They are sometimes called “proton sponges.” D) They are species with a proton affinity >1000 kJ/mole. 11. According to Basolo’s rules, which of the following insoluble sulfides is likely to be the most soluble? 2
A) Ag2S B) CdS C) Fe2S3 D) PbS 12. In which of the following sets are all of the metal hydroxides amphoteric? A) Cu(OH)2 , Mn(OH)2, Fe(OH)2, Fe(OH)3 B) Be(OH)2, Ca(OH)2, Ba(OH)2, Sr(OH)2 C) LiOH, NaOH, KOH, RbOH D) Al(OH)3, Zn(OH)2, Cr(OH)3, Sn(OH)2 13. Which reagent can be used to separate Al+3 from Zn+2? A) (NH4)2S B) NaOH C) NH3 D) H2SO4 14. Which reagent will distinguish between SO4‐2 (aq) and C2O4‐2 (aq)? A) Na+ B) Ca+2 C) Ba+2 D) Mg+2 15. (3 pts each) When the two atomic orbitals shown on the left below overlap and combine, is the bonding MO a) , π, or δ MO? __________________ b) g (gerade) or u (ungerade)? ______________________ dxy
dxy
Resulting MO
Nuclei approach along
the z axis shown
16. (12 pts) Assuming other equilibria are negligible, what is the silver ion concentration in a saturated solution of Ag2CO3 if the Ksp for Ag2CO3 is 8.4 x 10‐12? 17. (12 pts) Draw the molecular orbital diagram for BC and use it to answer the following questions. a. (5 pts) What is the bond order for BC? Is this consistent with the prediction from a Lewis Structure? Explain your reasoning. b. (5 pts) Is BC paramagnetic or diamagnetic? Is this consistent with the prediction from a Lewis Structure? Explain your reasoning. c. (3 pts) Which would be the most stable species, BC1‐, BC or BC1+? Explain your reasoning. 18. (12 pts) What is the pH of a solution that is 0.10 M HCN and 0.050 M NaCN? Ka = 4.9 × 10‐10 for HCN. 19. (17 pts) On addition of ammonium chloride and excess ammonia to an aluminum‐nickel group unknown, a white precipitate formed. When ammonium sulfide was added to the same solution, a black precipitate formed. The combined precipitates did not completely dissolve in hydrochloric acid, but completely dissolved when nitric acid was added. When this solution was treated with excess sodium hydroxide and hydrogen peroxide, a colorless solution and a light green precipitate resulted. What compounds are present, absent, and undetermined? Explain your reasoning and account for all the observations. 3
Chem 222 Exam 3 January 23, 2015 Name ________________ SHOW YOUR WORK. NO WORK, NO CREDIT INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers. On my honor, I pledge that I have upheld the Honor Code, and that the work I have done on this assignment has been
honest, and that the work of others in this class has, to the best of my knowledge, been honest as well.
Signed _________________________________________________________________
If you feel you can’t sign this, contact the instructor (email, or in person)
Silver Group: Ag, Hg, Pb Aluminum‐Nickel Group: Ni, Fe, Co, Mn, Al, Cr, Zn Copper‐Arsenic Group: Cu, Hg, Pb, As, Sb, Bi, Sn, Cd Barium‐Magnesium Group: Na, K, Mg, Ca, Ba, NH4+1 Constants and Equations Supplied on Exams
Zeff s/p: same n = 0.35, n-1 = 0.85,  n-2 = 1.00
1
2
d/f: same n = 0.35, rest = 1.00
1
particles
mole
m
J
L·atm
h = 6.626 x 1034 J·s c = 2.998 x 108
R = 8.314
= 0.08206
s
K·mole
K·mole
C
C
J
Amp =
F = 96500
= 96500
J = C·V
s
mole
V·mole
RT
RT
0.05916
E = E° ln (Q)
= 0.025693 V at 25 °C E = E° log (Q)
nF
F
n
0 °C = 273.15 K
 = 2.828   
s =  n(n  2) 2
N A = 6.022 x 1023
Circle the correct answer. (multiple choice = 2 pts each) 1. Manganese crystallizes in a body‐centered cubic structure. What is the coordination number of each atom? A) 12 B) 4 C) 8 D) 6 2. Metallic bonds are A) directional, and act between atoms of the same metal only B) directional, and act between any metal atoms C) nondirectional, and act between atoms of the same metal only D) nondirectional, and act between any metal atoms 3. The sphere packing that gives rise to a hexagonal structure is A) ... ABACABAC ... B) ... ABCABCABC ... C) ... ABABABAB ... D) none of the above 4. Which one of the following is not a general property of ionic solids? 1
5.
A) hard and brittle B) good electrical conductors in the solid state C) relatively high melting points D) positions of ions define the unit cell (lattice) White tin has an electrical conductivity that decreases with increasing temperature, and gray tin has an electrical conductivity that increases with increasing temperature. Therefore, white tin is classified as a(n) ________, and gray tin is classified as a(n) ________. 6.
A) insulator, metal B) metal, semiconductor C) semiconductor, metal D) metal, insulator An ionic compound crystallizes in a unit cell having a face‐centered cubic array of metal ions, Mn+, and all of the tetrahedral holes occupied by anions, X–1. The empirical formula of this ionic compound is A) MX2. B) M2X. C) MX. D) M7X4. 7.
The picture on the right represents a two‐dimensional lattice of atoms M and X. Which of the areas designated A, B, and C are unit cells for this 2‐D array? 8.
9.
A) only A B) only B C) only C D) A, B, or C Which of these materials in the band diagrams on the right is an insulator? A) material (1) B) material (2) C) material (3) D) material (4) Which picture represents a p‐type Si semiconductor? A) picture (A) B) picture (B) C) neither picture (A) nor picture (B) D) both picture (A) and picture (B) 10. What is the coordination number of the Fe atom in K3[Fe(en)3]? A) 2 B) 4 C) 6 D) 3 11. Which aqueous metal ion will reduce Ag+, but not Cu2+? A) Fe2+ B) Sn2+ C) Fe3+ D) Mn2+ 2
12. Which of the structures shown has each the three pairs of like ligands trans to each other? A) I B) II C) III D) IV 13. A galvanic cell uses the reaction: Cu(s) + 2 Ag+(aq)  2 Ag(s) + Cu2+(aq). If the initial concentrations of Ag+(aq) and Cu2+(aq) are both 1.0 M, what will happen to the cell voltage if 5.0 M Cu(NO3)2 (aq) is added to the compartment containing the 1.0 M Cu2+(aq)? The cell voltage will A) decrease. B) increase. C) remain the same. D) canʹt tell from the information given. 14. Which compound reacts with cold, concentrated H2SO4 to produce a colorless gas with a sharp, piercing odor? A) NaNO3 B) CaSO3 15. (3 pts) Name the complex ion [Co(en)2Cl2]1+ C) K2CrO4 D) Ag2AsO4 16. (3 pts) Write the formulas for the complex ion chlorotricyanonickelate(II) 17. (4 pts) Determine if the iron complex shown the  or  isomer. Explain your reasoning. 18. (2 pts each) In the figure shown, identify the step number that corresponds to: a) second ionization energy _________ b) electron affinity _________ c) lattice (formation) energy _________ d) Hf for MgCl2 _________ 6
3
19. Answer the following questions based on the accompanying picture in which the cations are represented by the small dark circles and the anions are represented by large open circles. a) (3 pts each) How many cations and how many anions are contained in one unit cell? _________ cations _________ anions b) (3 pts each) What is the coordination number of the cation and the anion? CN cation _________ CN anion _________ c) (2 pts) Which cubic cell do the anions form? A) simple cubic B) body centered cubic C) face centered cubic D) edge centered cubic d) (2 pts) The cations occupy which type of hole (or interstitial position) A) octahedral B) tetrahedral C) trigonal D) cubic e) (2 pts) Which type of unit cell is shown? A) wurtzite B) antifluorite C) zinc blende D) TiO2 (rutile) 20. (10 pts) Metallic calcium crystallizes in a face‐centered cubic lattice, and the atomic radius of calcium is 197 pm. Calculate the density of calcium in g/cm3. 21. (10 pts) How many grams of chromium metal are plated out when a constant current of 8.00 mA is passed through an aqueous solution containing Cr3+ ions for 40.0 minutes? 22. (16 pts) A solution may contain the following ions Ag+, Cu2+, Mn2+, Ca2+, and Na+. No precipitate formed when 0.10 M HCl was added but a dark colored precipitate formed when H2S was added to an acidic portion of the solution. After the removal of the solid the solution was made basic and more H2S was added and a colored precipitate formed. Treatment of the filtrate with (NH4)2CO3 resulted in a white precipitate. If no further tests were made then what conclusions can you draw? 4