May 3rd, 2012 Name:_____________________ CLID:_____________________ Score:_____________________
Chem 105 Final Exam There are 50 multiple choices that are worth 3 points each. There are 4 problems and 1 bonus problem. Try to answer the questions, which you know first, and then solve the problems, which you are not sure about. Here is the summary of the total 225 points plus 10 bonus points. Carefully read the questions. Good luck!
Multiple choices (50 total) 3 points each, the total is 150 points
Problems #1 15 points #2 20 points #3 15 points #4 25 points #5 (Bonus) 10 points Total 235 points
You could use your calculator. No notes or books of any sort may be used during the exam. I have neither given nor received aid on the exam. Signature and date ________________________________________________
I. Multiple Choices: (3 points each, 150 total points; Choose the best answer for each question) 1. Two natures of light are wave and particle. Wave nature means to have _____________ and particle nature of light is _____________
a) an electric field component and a magnetic field component; quantum b) an electric field component and a magnetic field component; photon c) emission and absorption; quantum d) emission and absorption; photon
Your answer:______________ 2. Which of the four quantum numbers (n, l, ml, ms) determines the orientation of an orbital and which of the four quantum numbers (n, l, ml, ms) determines the shape of an orbital respectively?
a) l; ml b) ml; n c) ml; l d) n; ml
Your answer:______________ 3. What is the correct order of the electromagnetic spectrum from shortest wavelength to longest wavelength?
a) Gamma Rays → X-rays → Ultraviolet Radiation → Visible Light → Infrared Radiation → Microwaves → Radio Waves
d) Gamma Rays → X-rays → Visible Light → Ultraviolet Radiation → Infrared Radiation → Microwaves → Radio Waves
c) Radio Waves → X-rays → Ultraviolet Radiation → Visible Light → Infrared Radiation → Microwaves → Gamma Rays
b) Visible Light → Infrared Radiation → Microwaves → Radio Waves → Gamma Rays → X-rays → Ultraviolet Radiation
Your answer:______________ 4. The maximum number of electrons that can occupy an energy level described by the principal quantum number, n, is ____________ .
a) n b) n + 1 c) 2n d) 2n2
Your answer:______________ 5. The first ionization energy is the minimum energy required to remove the first electron from the atom in its ground state. Which of the following atoms most likely has the highest first ionic energy?
a) 9F b) 12Mg c) 15P d) 56Ba
6. The hybridization of N in the NH3 molecule is _____________ in which _____________ new type of orbitals are generated.
a) sp2; 2 b) sp2; 3 c) sp3; 3 d) sp3; 4
Your answer:______________ 7. Determine ∆Hºrxn for the reaction 2Al2O3(s) → 4Al(s) + 3O2(g). You are given: 2Al(s) + (3/2)O2(g) → Al2O3(s), and ∆Hºrxn = –1,670 kJ/mol
a) 835 kJ/mol b) 1,670 kJ/mol c) 2,357 kJ/mol d) 3,340 kJ/mol
Your answer:______________ 8. 2.0 L of gas A at 1.00 atm and 1.00 L of gas B at 1.00 atm are combined in a 3.00 L flask. The flask is sealed and over time they react to completely to give gas C according to the following chemical equation: 2A(g) + B(g) → C(g). Assume constant temperature condition.
a) 0.33 atm b) 0.50 atm c) 0.67 atm d) 1.0 atm
Your answer:______________ 9. A ground-state atom of manganese has __________ unpaired electrons and is ____________.
a) 0, diamagnetic b) 2, diamagnetic c) 0, paramagnetic d) 2, paramagnetic
Your answer:______________ 10. Which of the following bonds has the longest bond length and which of the following bonds has the highest bond energy respectively?
a) C−N; C−N b) C−N; C≡N c) C≡N; C−N d) C≡N; C≡N
Your answer:______________ 11. Which one of the following pairs are isoelectronic?
a) Cl- and S b) K+ and Cl c) Na+ and K+ d) Zn2+ and Cu+
12. Which of the following substance is/are trigonal pyrimidal? (i) SO3 (ii) SO3
2– (iii) NO3– (iv) PF3 (v) BF3
a) only (i) and (ii) b) only (i), (iii), and (v) c) only (ii), and (iv) d) all are trigonal pyrimidal except (v)
Your answer:______________ 13. Arrange the following ions in order of increasing ionic radius: Na+, N3–, O2–, F–.
a) F– < O2– < N3– < Na+ b) F– < O2– < Na+ < P3– c) N3– < O2– < F– < Na+ d) Na+ < F– < O2– < N3–
Your answer:______________ 14. Give the number of lone pairs around the central atom and the molecular geometry of AsCl3.
a) 0 lone pair; trigonal planar b) 1 lone pair; trigonal pyrimidal c) 2 lone pairs; T shape d) 3 lone pairs; linear
Your answer:______________ 15. The correct order of increasing polarity is _____________ .
a) C-N < C-O < C-F < F-F b) C-O < C-F < F-F < C-N c) F-F < C-F < C-O < C-N d) F-F < C-N < C-O < C-F
Your answer:______________ 16. According to the valence shell electron pair repulsion (VSEPR) theory, the geometry of the SO2 molecule is _____________ and the geometry of the SO3 molecule is_____________
a) linear; trigonal planar b) linear; trigonal pyrimidal c) bent; trigonal planar d) bent; trigonal pyrimidal
Your answer:______________ 17. A single pulse of a laser yields an average of 5.00 × 1018 photons with λ = 633 nm. If melting ice to water at 0°C requires 6.01 kJ/mol, what is the fewest number of laser pulses need to melt 10.0 g of ice? h = 6.63 x 10-34 J·s
a) 2,127 b) 3,343 c) 3,833 d) 38,330
18. What is the maximum number of electrons in an atom that can have the following set of quantum numbers? n = 4; l = 3; ml = –2; ms = +1/2
a) 1 b) 2 c) 6 d) 10
Your answer:______________ 19. The standard enthalpy change for the following reaction is _____________ . 2C8H18(l) + 17O2(g) → 16CO(g) + 18H2O(l) given two following reactions: 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l) ∆H° = –11,020 kJ/mol 2CO(g) + O2(g) → 2CO2(g) ∆H° = –566.0 kJ/mol
a) -4,326 kJ/mol b) -6,492 kJ/mol c) -10,454 kJ/mol d) -11,586 kJ/mol
Your answer:______________ 20. The enthalpy change for the combustion of one mole of acetylene, C2H2, to form carbon dioxide and water vapor is -1,010.5 kJ. The reaction is under constant pressure and volume condition. What is the bond energy of C≡C (BEC≡C) in kJ/mol? Type of Bonds Bond Energy (kJ/mol) C–H 456 C−C 347 C=C 620 C=O 802 O=O 499 O–H 462
a) 799 kJ/mol b) 962 kJ/mol c) 1,035 kJ/mol d) 1,277 kJ/mol
Your answer:______________ 21. How many liters of chlorine Cl2 gas at 2.50 x 10 °C and 0.950 atm can be produced by the reaction of 12.0 g of MnO2 with excess HCl according to the following chemical equation? The molar mass of MnO2: 86.94 g/mol and the molar mass of Cl2: 70.9 g/mol, R = 0.0821 L·atm/(mol·K). (K = °C + 273) MnO2(s) + 4HCl(aq) → MnCl2(aq) + 2H2O(l) + Cl2(g)
a) 0.138 L b) 0.282 L c) 1.09 L d) 3.55 L
22. What are the correct numbers of dots surrounding the 33As symbol in the Lewis dot structure of 33As and surrounding the 33As3- symbol in the Lewis dot structure of 33As3- respectively?
a) 3; 0 b) 3; 6 c) 5; 0 d) 5; 8
Your answer:______________ 23. A 125.4 mL sample of 0.2763 M HNO3 is completely neutralized by 352 mL Al(OH)3. What is the concentration in molarity of Al(OH)3? 3HNO3 + Al(OH)3 Al(NO3)3 + 3H2O
a) 0.0109 M b) 0.0328 M c) 0.0984 M d) 0.295 M
Your answer:______________ 24. An aluminum (Al) metal reacts with hydrochloric acid (HCl) to form hydrogen gas (H2) and aluminum chloride. If the volume of H2 gas is 0.704 L and the pressure of H2 gas is 1.05 atm after the end of the reaction. Temperature of H2 gas is 22ºC. Calculate how many gram of Al was used in the reaction. Assuming the percent yield is 100%. R = 0.0821 atm·L/(K·mol)
a) 0.367 g b) 0.549 g c) 0.832 g d) 1.242 g
Your answer:______________ 25. Three students (X, Y, Z) are assigned the task of determining the mass of a sample of iron. Each student makes three determinations with a balance. The results in grams are X (61.5, 61.6, 61.4); Y (62.8, 62.2, 62.7); Z (61.9, 62.2, 62.1). The actual mass of the iron is 62.0 g. Student _____________ is the least precise and student ____________ is the most accurate.
a) X; Y b) X; Z c) Y; X d) Y; Z
Your answer:______________ 26. Ethylene (C2H4) burns in oxygen to form carbon dioxide (CO2) and water vapor. How many liter(s) of CO2 are obtained from 1.00 liter (L) of O2 at the constant temperature and pressure? C2H4 + 3O2 → 2CO2 + 2H2O
a) 0.667 L b) 1.00 L c) 1.50 L d) 2.00 L
27. Predict the geometry and polarity of the CS2 molecule. a) Bent; Nonpolar b) Bent; Polar c) Linear; Nonpolar d) Linear; Polar
Your answer:______________ 28. Indicate the type of hybrid orbitals used by the central atom in PF3.
a) sp b) sp2 c) sp3 d) sp3d
Your answer:______________ 29. Use the bond enthalpy data given to estimate the heat released when 50.0 g of propane gas, C3H8, burns in excess oxygen to yield carbon dioxide and water vapor at 25°C. Type of Bonds Bond Energy (or Enthalpy) (kJ/mol) C−C 347 C≡C 962 O=O 498 C=O 799 O–H 460 C–H 414
a) 1362 kJ/mol b) 1544 kJ/mol c) 2248 kJ/mol d) 2378 kJ/mol
Your answer:______________ 30. The Lewis structure for a carbonic ion, CO3
2-, should show ____ single bond(s), ____ double bond(s), and ____ lone pair(s).
a) 2, 1, 7 b) 2, 1, 8 c) 3, 0, 7 d) 3, 0, 9
Your answer:______________ 31. A chemist wishes to perform the following reaction:
N2 + 3H2 2NH3 If only 28.2 g of N2 is available, what is the minimum amount, in grams, of H2 needed to completely react with this quantity of N2?
a) 1.01 g b) 1.51 g c) 3.03 g d) 6.06 g
32. Which of the following ionic solids would have the smallest lattice energy? a) KF b) KI c) LiF d) NaF
Your answer:______________ 33. 18.00 g of glucose (C6H12O6) is dissolved in 0.100 L of water. The molarity (M) of the glucose solution is _______ . Assume that the final volume of the glucose solution is 0.100 L.
a) 0.0100 M b) 0.100 M c) 1.00 M d) 10.0 M
Your answer:______________ 34. Calculate the density in g/L, of CO2 gas at 2.70 x 10 °C and 0.500 atm pressure. R = 0.0821 L·atm/(mol·K). The molar mass of CO2: 44.0 g/mol. (K = °C + 273)
a) 0.893 g/L b) 1.12 g/L c) 2.93 g/L d) 4.02 g/L
Your answer:______________ 35. You are given a balanced reaction: 2H2 + O2 → 2H2O. How many moles of water could be made from 5.0 mol H2 and 3.0 mol O2 at the end of the reaction?
a) 1.5 mol b) 3.0 mol c) 5.0 mol d) 8.0 mol
Your answer:______________ 36. What is the oxidation number of S in H2SO4?
a) -2 b) +2 c) +4 d) +6
Your answer:______________ 37. What mass of Li3PO4 is needed to prepare 5.00 x 102 mL of a solution having a lithium ion concentration of 0.175 M?
a) 3.38 g b) 6.75 g c) 10.1 g d) 19.3 g
38. Give the values of all the quantum numbers associated with the electron in 3d shown in the following diagram.
a) ψ = fn(3, 1, -1, -1/2) b) ψ = fn(4, 1, -1, -1/2) c) ψ = fn(3, 2, -2, -1/2) d) ψ = fn(4, 2, -2, -1/2)
Your answer:______________ 39. The correct order of increasing electronegativity is ______________ .
a) As < Ga < K < Cs b) Cs < K < Ga < As c) Ga < As < K < Cs d) K < Ga < As < Cs
Your answer:______________ 40. List the following atoms and ions in an order of increasing atomic size: K+, Cl-, Ar, Ca2+, Cl
a) Ar < K+ < Ca2+< Cl < Cl- b) Ca2+ < K+ < Ar < Cl < Cl- c) Cl < Cl- < Ar < K+ < Ca2+ d) K+ < Ca2+ < Ar < Cl < Cl-
Your answer:______________ 41. According to Bohr’s theory, an electron originally in a higher-energy orbital falls back to a lower-energy orbital. As a result, a photon is given off. Calculate the wavelength, in nanometers, of the light emitted by a hydrogen atom when its electron falls from the n = 7 to the n = 4 principal energy level. RH = 2.18 x 10-18 J and h = 6.63 x 10-34 J·s.
a) 1.38 × 10-12 nm b) 9.18 × 10-7 nm c) 1.38 × 102 nm d) 2.17 × 103 nm
Your answer:______________ 42. According to Bohr’s theory, an electron originally in a higher-energy orbital falls back to a lower-energy orbital. As a result, a photon is given off. Calculate the frequency in s-1 (Hz) of the light emitted by a hydrogen atom during a transition of its electron from the n = 6 to the n = 3 principal energy level. RH = 2.18 x 10-18 J and h = 6.63 x 10-34 J·s.
a) 9.13 × 1013 s-1 b) 2.74 × 1014 s-1 c) 3.65 × 1014 s-1 d) 1.64 × 1015 s-1
1s 2s 2p 3s 3p 4s 3d1s 2s 2p 3s 3p 4s 3d
43. Valence shell and valence electrons of an atom of tellurium (52Te) are _____________ respectively?
a) 5; 4 b) 5; 6 c) 6; 4 d) 6; 6
Your answer:______________ 44. Electrons in an atom have the quantum numbers n = 3, l = 1, ml = 0. Name the orbital in which these electrons would be found.
a) 3dyz b) 3py c) 3dxz d) 3px
Your answer:______________ 45. Give the values of the four quantum numbers of an electron in the orbital of 3d.
a) n: 3; l: -2; ml: -2; ms: +1/2, -1/2 b) n: 3; l: -2; ml: -2, -1, 0, +1, +2; ms: +1/2, -1/2 c) n: 3; l: +2; ml: -2; ms: +1/2, -1/2 d) n: 3; l: +2; ml: -2, -1, 0, +1, +2; ms: +1/2, -1/2
Your answer:______________ 46. Which of the following atom and/or ions has/have this electron configuration?
a) Fe2+ and Co2+ b) Fe2+ and Cu2+ c) Mn d) Mn and Co2+
Your answer:______________ 47. The electron configurations of Zn2+ and Ge are ______________ respectively.
a) 1S22s22p63s23p64s23d8; 1S22s22p63s23p64s23d104p2 b) 1S22s22p63s23p64s03d10; 1S22s22p63s23p64s23d104p2 c) 1S22s22p63s23p64s23d8; 1S22s22p63s23p64s23d64p6 d) 1S22s22p63s23p64s03d10; 1S22s22p63s23p64s23d64p6
Your answer:______________ 48. The formal charge of C in HCN is ______________ .
a) -2 b) -1 c) 0 d) +1
1s2 2s2 2p6 3s2 3p6 4s2 3d51s2 2s2 2p6 3s2 3p6 4s2 3d5
49. The total number of lone pair in the NO2– ion is ______________ and the formal charge of N
in the NO2– ion is ______________.
a) 4; -1 b) 4; 0 c) 6; -1 d) 6; 0
Your answer:______________ 50. A 2.50-L flask contains a mixture of methane (CH4) and propane (C3H8) at a pressure of 1.45 atm and 20.0°C. When this gas mixture is then burned in excess oxygen, 8.60 g of carbon dioxide is formed. The other product is water. What is the mole fraction of propane in the original gas mixture? R = 0.0821 L·atm/(mol·K)
a) 0.148 b) 0.344 c) 0.656 d) 0.852
Your answer:______________ II. Problem Solving 1. Show all the resonance forms of HNO3. Calculate the formal charges for N atom and three O atoms in all the resonance forms of HNO3. Show your calculations for the formal charges of any one of the resonance forms of HNO3. (Total 15 points and showing the calculation is 4 points)
2. Write Lewis structures for the following molecules. (20 points, 4 points each) (a) CH4O2 (b) H3PO4 (c) CO (d) C2H5Cl (e) CH4N2O
3. Draw the dipole moment for each bond and the resultant dipole moment if not zero, for the following molecules. Specify whether each molecule is nonpolar or polar. Justify your answers. (15 points, 5 points each) (i) CH4 (ii) SO2 (iii)H2O 4. When a 0.952 g sample of an organic compound CxHyOz containing C, H and O is burned in completely in oxygen, 1.35 g of CO2 and 0.826 g of H2O are produced. What is the empirical formula of the compound? Show your calculations. (25 points)
5. Bonus question (total 10 points). IT IS GREAT TO KNOW YOU! I BELIEVE YOU HAVE TRIED YOUR BEST IN THIS COURSE! HAVE A GOOD WINTER BREAK! BEST WISHES! (a) What is the molar concentration of chloride ions in a solution prepared by mixing 50.0 mL of 2.00 M KCl with 100.0 mL of a 1.50 M CaCl2 solution? Assume the final volume is additive. Show your calculations or justify your answer. (5 points) (b) Show the Lewis structure of N2O and calculate the formal charges on the two nitrogen atoms and one oxygen atom in N2O? Show your calculations. (5 points)