1. Which molecule or ion does NOT have a pyramidal shape? + 2. Which of these molecules or ions contains a multiple bond? (D) H 2.

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1 CHEM 1411 Name: Dr. Julie Burrell (Key) Exam 3. Summer I 2017 Questions 1-23, multiple choice questions. 3 points each. 1. Which molecule or ion does NOT have a pyramidal shape? + - (A) SF 3 (B) all are pyramidal (C) NO 3 (D) H 3 O + (E) PH 3 2. Which of these molecules or ions contains a multiple bond? (A) CH 3 CH 2 Br (B) BH 3 (C) COCl 2 (D) H 2 O 2 (E) N 2 H 4 3. Which of the following lists of atoms are arranged in order of INCREASING ionization energy? (A) Li < O < N < F (B) Li < N < O < F (C) F < O < N < Li (D) Na < Sr < O < F (E) Ca > Cs > S > Se 4. Which of these triatomic molecules or ions will exhibit a 180 degree bond angle around the central atom? (A) H 2 O (B) KrF 2 (C) ClO 2 - (D) SCl 2 (E) NO 2 -

2 5. The noble gases are (A) monatamic (B) have filled s and p subshell (C) are generally unreactive (D) all of the above 6. Select the correct electron configuration for Te (A) [Kr]5s 2 4d 10 5p 4 (B) none of these (C) [Kr]5s 2 5p 6 4d 8 (D) [Kr]5s 2 5d 10 5p 4 (E) [Kr]5s 2 4f Suppose that a metal oxide of formula M 2 O 3 were soluble in water. What would be the major product or products of dissolving the substance in water? (A) MH 3 (aq) + O 2 (g) (B) M(s) + H 2 (g) + O 2 (g) (C) 3M (aq) H 2 O 2 (aq) (D) M(OH) 2 (aq) (E) M(OH) 3 (aq) 8. Select the element with the largest second ionization energy [IE 2 ] (A) Al (B) Rb (C) Sr (D) Ca (E) K 9. Which of the following Lewis dot structures is INCORRECT? (A) (B) (C) (D) (E) None of the above is incorrect

3 10. Arrange the following molecules in terms of INCREASING F-A-F angle [where A represents the central atom]: BF 3, CF 4, NF 3 (A) BF 3 < NF 3 < CF 4 (B) none of these is correct (C) CF 4 < BF 3 < NF 3 (D) NF 3 < CF 4 < BF 3 (E) CF 4 < NF 3 < BF Which of the following molecules contains an EXCEPTION to the octet rule? (A) CO (B) C 2 H 6 (C) NF 3 (D) N 2 H 4 (E) ClF In a phosphorous-chlorine bond, the bond is and the atoms bears charge (A) polar, P, a partial negative (C) polar, P, a partial positive (E) polar, Cl, a partial positive (B) nonpolar, Cl, no partial (D) nonpolar, P, no partial 13. Which of the following equations correctly represents the process involved in the electron affinity of X? (A) X + (g) + e - => X(g) (B) X + (g) + Y - (g) => XY(g) (C) X(g) + e - => X - (g) (D) X(g) => X + (g) + e- (E) X + (g) => X + (aq) 14. The third ionization energy of bromine is the energy required for which of the following processes? (A) Br(g) == Br + (g) e - (B) Br + (g) == Br 2+ (g) e - (C) Br(g) == Br 2+ (g) 2e - (D) Br(g) == Br 3+ (g) 3e - (E) Br 2+ (g) == Br 3+ (g) e -

4 15. Which of the following is incorrectly matched with the correct type of bonding? (A) OCl 2, covalent (B) Al, metallic (C) CO, covalent (D) SrF 2, ionic (E) NI 3, ionic 16. How many unpaired electrons are there is a ferric ion (Fe 3+ )? (A) 4 (B) 3 (C) 1 (D) 2 (E) What is the formal charge on nitrogen in the NO + ion: [:N O:] + (A) -1 (B) -2 (C) +2 (D) 0 (E) Select a correct set of quantum numbers (n, l, m l, m s ) for the highest energy electron in the ground state of tin, Sn (A) 5, 1, 2, +1/2 (B) 5, 2, -1, 1/2 (C) 5, 1, 1, 1 (D) 5, 1, 0, +1/2 (E) 5, 2, 0, -1/2 19. Which of the following lists of atoms are arranged in order of INCREASING size? (A) Se > Si > Sb > Bi (B) Cs < Sr < Pb < I (C) Cs < Ca < Rb < Sr (D) Br < Sr < Ba < Cs (E) Ca < Cs < Sr < Rb 20. Consider the set of isoelectronic atoms and ions A 2-, B -, C, D + and E 2+. Which arrangement of relative radii is correct? (A) A 2- > B - > C < D + > E 2+ (B) A 2- < B - < C > D + < E 2+ (C) A 2- > B - > C > D + > E 2+ (D) none of these (E) E 2+ > D + > C > B - > A Which of these elements is most likely to form ions with a 2+ charge?

5 (a) Li, (b) Ca, (c) O, (d) P (e) Cl 22. Which of these molecules has the same number of shared and unshared electron pairs? (A) HCl, (B) H 2 S, (C)PF 3, (D) CCl 2 F 2 (E) Br Which of the following bonds is the most polar? (A) H F, (B) H I, (C) Se F, (D) N P, (E) Ga Cl Questions 24-30, 5 points each. Show your work to have full credit 24. Consider the following AB 3 molecules and ions: PCl 3, SO 3, AlCl 3, SO 3 2-, and CH 3+. How many of these molecules and ions do you predict to have a trigonalplanar molecular geometry? (A) 1 (B) 2 (C) 3 (D) 4 (E) Which of these molecules has a Lewis structure with a central atom having no nonbonding electron pairs? (A) CO 2, (B) H 2 S, (C) PF 3, (D) SiF 4, (E) more than one of a, b, c, d.

6 26. Draw the Lewis structure(s) for the molecule with the chemical formula CH 3 CN, where the N is connected to only other atom. How many double bonds are there in the correct Lewis structure? (A) zero, (B) one, (C) two, (D) three, (E) four. 27. For each compound, state the electron domain (steric number), molecular geometry, molecular shape, hybridization of the central atom, the electron domain geometry Electron domain molecular geometry molecular shape hybridization A) PI 5 B) SO 2 C) AsF 3

7 D) MgCl Consider the following oxides: How many are expected to form acidic solutions in water? SO 2, Y 2 O 3, MgO, Cl 2 O, and N 2 O 5. (a) 1 (b) 2 (c) 3 (d) 4 (e) Predict which one of the following orderings of lattice energy is correct for these ionic compounds. (A) NaCl > MgO >CsI > ScN, (B) ScN > MgO > NaCl > CsI, (C) NaCl > CsI >ScN > CaO, (D) MgO >NaCl > ScN > CsI, (E) ScN > CsI > NaCl > MgO. 30. Select the lattice energy for rubidium chloride from the following data [in kj/mol] Rb(s) => Rb(g) ΔH = 85.8 IE1(Rb) ΔH = BE(Cl 2 ) ΔH = 226 ΔH f (RbCl) = -431 EA Cl = -332 (A) (B) (C) -695 (D) -808 (E) +808

8 Questions Extra credit 10 points each. Show your work. No partial credit. 31. Use the bond energies given below to calculate the enthalpy change for the reaction, HCN(g) + 2 H 2 (g) => CH 3 NH 2 (g) Bond Bond Energy (kj/mol) Bond Bond Energy (kj/mol) H-H 432 C-H 413 C-N 305 C=N 615 C N 891 N-H 391 (A) -590 kj/mol (B) -158 kj/mol (C) +18 kj/mol (D) +133 kj/mol (E) +158 kj/mol 32. Below are following MO diagrams for O 2 and N 2. (a) what is the bond order of each molecule (b) how many unpaired electrons does it molecule has? (c) which molecule is diamagnetic? (d) which molecule is paramagnetic

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12 Key SF 3 + NO 3 - H 3 O + PH 3 1. C All are trigonal pyramidal except NO 3 - which is trigonal pyramidal. 2. C 3. A or D is correct answer Ionization energy increases up a group and increases across a period. 4. B 5. D 6. A 7. E 8. E

13 9. E 10. D ( , 120 ) 11. E 12. C 13. C 14. E 15. E. NI 3 is covalent 16. E 17. E Formal charge = # of valence electron [non bonded electrons pair + number of bonds] 18. D Formal charge for N = 5 (1 + 3) = 5 4 = 1 [Kr] 4d 10 5s 2 5p 2 n = 5, l = 1, m I = +1, 0, -1, m s = +1/2

14 19. D Atomic size increases down a group and decreases across a period. 20. C Anions have larger radii than cations. The greater the charge on the anion, the bigger the ion. The greater the charge on a cation, the smaller the anion. 21. B Ca is in group IIA (2) and will have +2 charge. 22. B 23. A 24. C SO 3, AlCl 3 and CH E ( A and D)

15 26. A 27. For each compound, state the electron domain (steric number), molecular geometry, molecular shape, hybridization of the central atom, the electron domain geometry Electron domain molecular geometry molecular shape hybridization A) PI 5 5 trigonal bipyramidal trigonal bipyramidal sp 3 d B) SO 2 4 tetrahedral bent sp 3 C) AsF 3 5 tetrahedral trigonal pyramidal sp 3 D) MgCl 2 2 linear linear sp 28. C (SO 2, Cl 2 O, N 2 O 5 ) 29. B - Lattice energy increases with the charge on the ion. - Lattice energy also increases with decreasing size on the ions. The higher the charge on the ions, the greater the energy the energy holding them together This is the biggest factor. The smaller the distance between the two ions, the higher the lattice energy. 30. H f = H sub + ½ BE + IE 1 + E.A. + lattice Energy (L.E) L.E. = H f - H sub - BE - IE 1 - E.A. = (-332) = kj/mol

16 31. H = B.E. reactants - B.E. products) = [( = 2(432)) (3(413) (391))] = = kj/mol 32. O 2 (a) ½ bonding electrons nonbonding electrons = ½ (8 4) = ½(4) = 2 (b) 2 (c) No (d) Yes, O 2 (unpaired electrons in the MO diagram) N 2 (a) ½ (10 4) = ½ (6) = 3 (b) 0 (c) Yes, N 2 ( means all the electrons in the MO diagram are paired) (d) No