NO CALCULATORS MAY BE USED FOR THESE QUESTIONS Questions 1-3 refer to the following list. (A) Cu (B) PH 3 (C) C (D) SO 2 (E) O 2 1. Contains instantaneous dipole moments. 2. Forms covalent network solids. 3. Exists as a lattice structure held together by delocalized electrons. 4. Sodium chloride is least soluble in which of the following liquids? (A) NH 3 (B) H 2 O (C) C 6 H 6 (D) C 2 H 5 OH (E) CH 3 COOH 5. Methanol, CH 3 OH, has a higher boiling point than ethene, C 2 H 4. Which of the following statements best accounts for this difference? (A) Methanol exhibits stronger London (dispersion) forces than ethene. (B) Methanol is a covalent network solid and ethane is not. (C) Methanol has a higher density than ethane. (D) Methanol exhibits dipole to dipole forces and ethane does not. (E) Methanol exhibits hydrogen bonding and ethane cannot. 6. Which of the following substances exhibits the greatest dipole moment? (A) CO (B) HF (C) CH 4 (D) PH 3 (E) F 2 7. Which of the following substances is a nonpolar molecule that contains polar bonds? (A) Cl 2 (B) CHF 3 (C) HF (D) NH 3 (E) CO 2
8. Which of the following substances would be expected to exhibit the highest melting point? (A) F 2 (B) Cl 2 (C) Br 2 (D) I 2 (E) N 2 Substance Equilibrium Vapor Pressure (mmhg) Acetaldehyde 740 Methyl isobutyl ketone 19.95 Benzene 75 Ethanol 43.7 Propanol 18.0 9. Based on the data in the table provided above, which of the following liquid substances has the weakest intermolecular forces? (A) Acetaldehyde (B) Methyl isobutyl ketone (C) Benzene (D) Ethanol (E) Propanol Ion Ionic Radius (pm) Mg 2+ 86 Ca 2+ 114 Sr 2+ 132 10. Based on the data in the table above, which of the following correctly predicts the relative strength of attraction of Mg 2+, Ca 2+, and Sr 2+ ions to water molecules in a solution, from strongest to weakest, and provides the correct reason? (A) Mg 2+ > Ca 2+ > Sr 2+ because smaller ions have a stronger coulombic attraction to the water molecules (B) Mg 2+ > Ca 2+ > Sr 2+ because the smaller ions experience a stronger nuclear charge (C) Mg 2+ > Ca 2+ > Sr 2+ because the smaller ions experience greater electronegativity (D) Sr 2+ > Ca 2+ > Mg 2+ because larger ions have more instantaneous dipoles or are more polarizable (E) Sr 2+ > Ca 2+ > Mg 2+ because the larger ions have greater shielding
11. In the diagram above, which of the following arrows identifies the hydrogen bonding in ammonia? (A) A (B) B (C) C (D) D (E) E 12. Lewis electron-dot diagrams of CO 2 and NO 2 - are given above. The molecular geometry and polarity of the two substances are (A) The same because the molecular formulas are similar. (B) The same because each exhibits pi bonding. (C) The same because both molecules are linear. (D) Different because the lone pair of electrons on the N atom make it the negative end of a dipole. (E) Different because N has a greater number of electron domains (regions of electron density) surrounding it as compared to C. 13. Which of the following solid compounds requires heat to break the lattice energy in order to melt? (A) CCl 4 (B) CaCl 2 (C) BrCl (D) PCl 3 (E) Cl 2 O
14. The diagrams above show molecules of Cl 2 and Br 2 drawn to the same scale. Which of the following is the best explanation for Cl 2 being a gas at room temperature as opposed to liquid Br 2? (A) Liquid bromine is a network covalent substance, whereas gaseous chlorine is a London dispersion forces gas. (B) The covalent bonding between Br 2 is weaker than those in the Cl 2 molecules. (C) The bond length of Br 2 is longer as opposed to the shorter bond lengths of Cl 2. (D) Br 2 molecules have electron clouds that are more polarizable than those of Cl 2 molecules, therefore the London dispersion forces are stronger in liquid Br 2. (E) Cl 2 has a greater electronegativity than Br 2, therefore they have stronger dipole to dipole attractions. 15. What is the best reason for H 2 O having a higher boiling point as compared to H 2 S? (A) H 2 O is polar whereas H 2 S is nonpolar (B) H 2 O exhibits hydrogen bonding whereas H 2 S exhibits London (dispersion) forces (C) H 2 O exhibits hydrogen bonding whereas H 2 S exhibits dipole to dipole interactions (D) H 2 O is a liquid whereas H 2 S is a gas (E) H 2 S is more polarizable due to the greater amount of electrons 16. Of the following pure substances, which has the highest melting point? (A) SiO 2 (B) S 8 (C) I 2 (D) SO 2 (E) C 6 H 6 17. Iron, Fe, can be made into an alloy by mixing other elements such as carbon (C) or Manganese (Mn). If the same mole fraction of C and Mn are introduced separately into samples of Fe, which of the following is the best explanation for the Fe-C alloy being harder than the Fe-Mn alloy? (A) C is a nonmetal whereas Mn is a metal. (B) C atoms are smaller than Mn atoms, therefore they interfere more with the displacement of atoms in the alloy. (C) Mn atoms are less polarizable than the C atoms, therefore Mn has weaker intermolecular forces. (D) C atoms have a higher melting point than Mn atoms. (E) Mn atoms have similar metallic forces to the Fe, therefore the properties do not change much when made into an alloy.
18. Based on the data in the tables above, which of the following statements provides the best prediction for the melting point of NaBr? (A) NaBr will have a higher melting point than MgO because the energy required to transfer electrons is larger in NaBr than in MgO. (B) NaBr will have a higher melting point than MgO because the ions are spaced further apart. (C) NaBr will have a melting point in between that of NaF and MgO because the ionic character of the bonds in NaBr is in between that of NaF and MgO. (D) NaBr will have a lower melting point than NaF because the coulombic attractions are weaker in NaBr than in NaF. (E) NaBr will have a lower melting point than MgO due to the lower covalent character of the bonds in NaBr. Compound Molecular Formula Molar Mass (g/mole) Boiling Point ( C) decane C 10 H 22 142 174 2-bromobutane C 4 H 9 Br 137 91 19. According to the data table above, the two molecules represented above have comparable molar masses and yet extremely different boiling points. Which of the following statements best helps to explain this data? (A) The C-Br bond of 2-bromobutane has smaller bond energy compared to the C-H bonds of decane. (B) The C-Br bond of 2-bromobutane is more polar than the C-H bonds of decane. (C) The carbon chains are longer in decane than they are in 2-bromobutane. (D) The carbon chains are farther apart in a sample of decane than they are in 2-bromobutane. (E) The decane molecule contains covalent network bonds which take more energy to break. 20. Semiconductors are materials that have a degree of electrical conductivity between a metal and an insulator. Silicon crystals are semiconductors that increase in conductivity when a small fraction of Si atoms are replaced by those of a different element. Which reason best accounts for this property change? (A) Ge atoms experience greater shielding than Si atoms. (B) P atoms introduce additional mobile positive charges. (C) P atoms introduce additional mobile negative charges. (D) C atoms introduce hardness to the material. (E) Ge atoms have more electrons than Si atoms.