Chemistry 113 Practice Exam 4 Spring 2016
Directions on actual Exam: The exam consists of 2 sections (Chemical Bonding and Geometry and IMFs. Each multiple choice question is worth 4.33 points. You are allowed to use a scientific (nonprogrammable) calculator, periodic table, and VSEPR Theory Table.
ΔH°rxn = Σn×D(bonds broken) – Σn×D(bonds formed)
where Σn represents the sum of the moles of a particular type of bond
D represents bond energy per mole of bond
Chemical Bonding and Geometry
The Lewis dot symbol for the calcium ion is
The electron dot structure for AsCl3molecule shows
a total of 84 electron dots
three single bonds and 10 lone pairs
two single bonds, one double bond, and 9 lone pairs
one single bond, two double bonds, and 8 lone pairs
three single bonds and one lone pair
The correct Lewis structure for CO2 is: C
Which of the following Lewis structures is incorrect?
How many covalent bonds will be formed by bromine in BrO3– for the dot structure that expands the octet to minimize formal charge and places negative formal charges on only the most electronegative atom(s). The Pauling electronegativity values are:
Br = 2.8; O = 3.5
Estimate the enthalpy change for the reaction 2CO + O2® 2CO2 given the following bond energies.
BE(CºO) = 1074 kJ/mol
BE(O=O) = 499 kJ/mol
BE(C=O) = 802 kJ/mol
Give the number of lone pairs around the central atom and the molecular shape of the ion ClO3–.
0 lone pairs, trigonal
1 lone pair, bent
1 lone pair, trigonal pyramidal
2 lone pairs, T-shaped
2 lone pairs, trigonal
Which of the following substances is/are bent?
(i) H2S (ii). CO2 (iii) ClNO (iv) NH2– (v) O3
only (i) and (v)
only (i), (iii), and (v)
all are bent except for (iv)
all are bent except for (ii)
Which of the following molecules is polar?
Indicate the type of hybrid orbitals used by the central atom in TeF4.
The hybridization of the O atom in CO2 will be
The number of pi bonds in the molecule below is
13. Order the forces (dipole-dipole, London dispersion, ionic, and hydrogen-bonding) from weakest to strongest .
a) dipole-dipole, London dispersion, ionic, and hydrogen-bonding
b) London dispersion, dipole-dipole, hydrogen-bonding, and ionic
c) hydrogen-bonding, dipole-dipole, London dispersion, and ionic
d) dipole-dipole, ionic, London dispersion, and hydrogen-bonding
e) London dispersion, ionic, dipole-dipole, and hydrogen-bonding
14. Which of the following would you expect to have the highest boiling point?
e) All of the above have the same boiling point.
15. The molecules in a sample of SO2 are attracted to each other by a combination of
a) London forces and H-bonding
b) H-bonding and ionic bonding
c) covalent bonding and dipole-dipole interactions
d) London forces and dipole-dipole interactions
e) none of these
16. When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction?
a) a hydrogen from one molecule and a hydrogen from the other molecule
b) a hydrogen from one molecule and an oxygen from the other molecule
c) an oxygen from one molecule and an oxygen from the other molecule
d) an oxygen and a hydrogen from the same molecule
e) two hydrogens from one molecule and one hydrogen from the other molecule
Chemical Bonding and Geometry
17. Which formula is matched with the correct number of valence electrons in the free (not bonded) central atom, bonds, and lone pairs in the molecule for the underlined atom?
a. SeH2; 6 valence electrons, 2 bonds, and 1 lone pair
b. SiCl4; 4 valence electrons, 4 bonds, and 0 lone pairs
c. FCl; 1 valence electron, 1 bond, and 0 lone pairs
d. SCl2; 6 valence electrons, 2 bonds, and 0 lone pairs
e. PH3; 4 valence electrons, 3 bonds, and 1 lone pair
18. The electron-dot structure for the species NH4O+ contains
a. 1 double bond and 4 single bonds
b. 5 single bonds and 3 lone pairs.
c. 5 single bonds and 2 lone pairs.
d. 5 single bonds and 1 lone pair.
e. 5 single bonds and zero lone pairs.
19. What is the hybridization of the carbon atom in CO2?
20. Which of the following molecules requires two resonance hybrid Lewis structures to account for the bonding?
21. Which of the following is the best electron-dot description for sulfur dioxide, SO2?
22. Which of the following compounds (or ions) contains an atom that does NOT follow the octet rule?
23. What is atom X in the Lewis structure of the following anion?
24. Which of the following statements is correct?
a. Covalent bonds usually involve two nonmetals and ionic bonds usually involve two metals.
b. Covalent bonds usually involve two metals and ionic bonds usually involve a metal and a nonmetal.
c. Covalent bonds usually involve a metal and a nonmetal and ionic bonds usually involve two nonmetals.
d. Covalent bonds usually involve two nonmetals and ionic bonds usually involve a metal and a nonmetal.
e. Covalent bonds usually involve two metals and ionic bonds involve two nonmetals.
25. The molecular structure of the IO3– ion is best described as:
a. bent or angular.
b. trigonal planar.
c. trigonal pyramidal.
d. trigonal bipyramidal.
26. The electron domain geometry of the AsF6– ion is octahedral. The hybrid orbitals used by the As atom for bonding are:
27. The F-B-F bond angle in BF3 is ____________.
28. The geometry associated with sp hybridization is:
c. trigonal biplanar
d. trigonal planar
29. Which series of elements is arranged in order of increasing electronegativity?
a. C, Si, P, As, Se
b. O, P, Al, Mg, K
c. Na, Li, B, N, F
d. K, Mg, Be, O, N
e. Li, Be, B, C, Ca
Use the following to answer questions 30-32:
Consider the representations below to answer the next three questions.
30. How many of the following statements are correct concerning drawing I?
Each molecule induces a dipole onto the next molecule in close proximity.
The phenomenon shown is relatively weak and short-lived.
All nonpolar molecules contains this type of interaction.
The forces that exist in this example are London dispersion forces.
31. Which drawing best represents the interactions in a sample of HF?
d) I, II
e) all of the above
32. Which of the following statements are incorrect concerning drawing III?
a) Electrostatic interactions exist between the molecules.
b) The molecules find the best compromise between attraction and repulsion.
c) These molecules exhibit ionic bonding.
d) CHCl3 exhibits this type of interaction.
e) Two of the above statements are incorrect.
33. Which of the following is the correct order of boiling points for KNO3, CH3OH, C2H6, Ne?
a) Ne < CH3OH < C2H6 < KNO3
b) KNO3 < CH3OH < C2H6 < Ne
c) Ne < C2H6 < KNO3 < CH3OH
d) Ne < C2H6 < CH3OH < KNO3
e) C2H6 < Ne < CH3OH < KNO3
34. What is the strongest intermolecular force (IMF) found in a sample of thousands of C2H6 molecules?
a. London b. dipole dipole c. nonpolar d. H bond force e. polar
35. What is the strongest intermolecular force (IMF) found in a sample of thousands of HBr molecules?
a.London b. dipole dipole c. nonpolar d. H bond force e. polar
36. What is the strongest intermolecular force (IMF) found in a sample of thousands of He atoms?
a. London b. dipole dipole c. nonpolar d. H bond force e. polar
37. What holds the N atom to the H atom in a molecule of ammonia, NH3?
a.Ionic bond b. polar bond c. H bond d. nonpolar bond e. dipole dipole
38. What holds the molecules together in a sample of ammonia, NH3?
a. Dipole dipole forces b. polar bonds c. H bond forces d. London forces
39. What holds the O atoms to each other in a molecule of oxygen gas?
a. Ionic bond b. polar bond c. H bond d. nonpolar bond e. dipole dipole
40. As intermolecular forces increase, which of the following decreases?
a. Surface tension b. Boiling Point c. Vapor Pressure d. Melting Point e. Viscosity
41.Which is true when comparing samples of C6H6(l) (has C-H bonds) to C2H5OH(l) (has an O-H bond)?
a The vapor pressure of C2H5OH is higher.
b. The boiling point of C6H6 is higher.
c. The surface tension of C2H5OH is lower.
d. The melting point of C2H5OH is lower.
e. The viscosity of C6H6 is lower.
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