CHEM 105 Exam 2 Practice PDF

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Chemistry 105 Practice Exam 2 Multiple Choice Section 1. How many valence electrons does aluminum have? a. 1 b. 2 c. 3

d. e.

11 13

2. Which of the following ranks the compounds from lowest to highest lattice energy? a. NaF < MgF2 < CaF2 < KF d. CaF2 < KF < NaF < MgF2 b. KF < NaF < CaF2 < MgF2 e. MgF2 < CaF2 < KF < NaF c. MgF2 < CaF2 < NaF < KF 3. How many nonbonding electrons are there in the Lewis structure of SCO? a. 0 d. 10 b. 4 e. 12 c. 8 4. What is the approximate carbon–oxygen bond order in the acetate ion, CH 3COO−? a. 0.5 d. 2 b. 1 e. 2.5 c. 1.5 5. Use the formal charge as a criterion to identify the Lewis structure below that is the best in representing the bonding in sulfur dioxide. a.

d.

b.

e.

c. 6. Resonance structures indicate that __________ a. there is more than one allotropic form of a compound. b. more than one ionic form of a compound exists. c. a molecule’s electronic structure is an average or superposition of all possible Lewis structures. d. more than one isotopic form of an element exists in the molecule. e. the molecule jumps back and forth between two or more different electronic structures. 7. Which of the following molecules is NOT polar? a. PCl3 b. H2O c. SO2

d. e.

CO2 N2O

8. Which of the following is a planar molecule? a. NH3 b. PCl5 c. KrF4

d. e.

CH3COOH SiH4

9. What is the hybridization of carbon in COCl2? a. sp2 b. sp3 c. sp3d

d. e.

sp sp3d 2

10. Which of the following has the largest bond angle? a. CF4 b. NF3 c. OF2

d. e.

NF2– NH3

11. Which statement regarding a σ bond between two carbon atoms linked by a single bond is NOT correct? a. The region of electron density lies along the bond axis connecting the nuclei of the two atoms. b. The bond can be described by the overlap of sp hybrid orbitals from each atom. c. The bond can be described by the overlap of sp2 hybrid orbitals from each atom. d. The bond can be described by the overlap of sp3d hybrid orbitals from each atom. e. The bond can be described by the overlap of an sp2 hybrid orbital from one atom with an sp3 hybrid orbital from the other atom. 12. What is the formula for n-nonane? a. CH3(CH2)9CH3 b. CH3(CH2)7CH3 c. CH3(CH2)17CH3

d. e.

CH3(CH2)5CH3 CH3(CH2)8CH3

13. Which type of molecular orbital is used to describe a buildup of electron density along the axis connecting two atomic nuclei to form a bonding orbital? a.  d. * e. py b.  c. * 14. Oxygen has two common molecular anions: peroxide (O22–) and superoxide (O2–). Use the MO energy level diagram below to identify which one of the following statements is NOT correct.

a. b. c. d. e.

The bond order of the peroxide is 1. The superoxide has a shorter bond than the peroxide. Like O2, the peroxide is paramagnetic. The superoxide has a stronger bond than the peroxide. Oxygen, O2, has a stronger bond than either of these oxides.

16. Use energy levels of diatomic molecules derived from molecular orbital theory to predict the bond order of the oxygen molecule O2 and the peroxide anion O22–.

a. b. c. d. e.

oxygen, bond order = 2; peroxide, bond order = 3 oxygen, bond order = 2; peroxide, bond order = 2 oxygen, bond order = 4; peroxide, bond order = 4 oxygen, bond order = 4; peroxide, bond order = 5 oxygen, bond order = 2; peroxide, bond order = 1

17. The molecular weight of a gas that has a density of 7.10 g/L at 25.0°C and 1.00 atm pressure is __________ g/mol. a. 68.8 b. 174 c. 56.2 d. 14.6 e. 128.0 18. How many He atoms are found in a party balloon with 2 L volume on a warm day at the North Pole (T=0°C)? The North Pole is at sea level. a. 5 x1024 b. 5 x 1022 c. 12x1023 19. Under similar conditions, which of the following gases would be predicted to behave less like an ideal gas than the others? a. Ar b. NH3 c. CH4 d. H2 e. O2

20. For equal amounts of molecules at the same pressure and temperature, which compound has the narrowest distribution of molecular speeds? a. CO2 b. SO2 c. C3H8 21. The pressure in a balloon filled with 3 L of gas at STP is decreased by ½ while the volume and number of moles remain constant. What is the new temperature inside the balloon? a. -136 C b. 273 C c. 0 C

Free Response Section 1.

Write the corresponding name or chemical formula for each chemical formula or name given below. a. CuCl2 Copper(II) chloride b. Ammonium carbonate (NH4)2CO3 c. Mg3(PO4)2 Magnesium phosphate d. Sodium sulfate Na2SO4 e. KHCO3 Potassium bicarbonate or potassium hydrogen carbonate f. Disulfur tetroxide S2O4 g. PH3 Phosphorus trihydride h. Tetraphosphorus decoxide P4O10 i. H2S (aq) Hydrosulfuric acid j. Nitrous acid HNO2

2.

Which of the following bonds is considered to be ionic? C O, Ca Cl, S N, or Si O. Explain your answer.

Ca Cl is considered to be ionic because the electronegativity difference between calcium and chlorine is so large, ionic bonds normally form between metal cations and non-metal anions. The other bonds listed all have smaller differences in electronegativity and are covalent, meaning that they share valence electrons. 3.

For each of the following molecules (O3, SCl2, SO2, CS2, and CO2), draw the Lewis dot structure, including formal charges and resonance where appropriate, and give the expected bond angles for each molecule.

Ozone:...