CHM-101-A Exam 4 Answers

CHM-101-A Exam 4 December 5, 2006 Version 1 1. Which of the following statements is correct? A. Since acetone (nail polish remover) evaporates more readily than water, one would assume that acetone has weaker intermolecular forces. B. The phase change from solid to gas is exothermic. C. Evaporation is an exothermic process, since heat is given off when a substance vaporizes. D. A liquid which has a high boiling point has a higher vapor pressure at a given temperature than a liquid with a low boiling point. E. Liquids boil at higher temperatures in the mountains due to the higher altitude. 2. Which of the following is not an attractive force that acts between the individual molecules of CH3OH? A. covalent bonds B. London dispersion forces C. dipole-dipole forces D. hydrogen-bonding forces E. none of these is correct 3. The physical properties of a substance that are influenced by the strength of intermolecular forces include all of the following except: A. melting point. B. vapor pressure. C. mass. D. boiling point. E. viscosity. 4. Which of the following substances is most likely to be a gas at room temperature and atmospheric pressure? A. Pb B. C8H18 C. I2 D. CCl4 E. Ar 5. Rank the following substances in order of increasing boiling point: Cl2, Ar, Ne, Br2 A. Ne < Ar < Cl2 < Br2 B. Ne < Ar < Br2 < Cl2 C. Cl2 < Br2 < Ar < Ne D. Cl2 < Ar < Ne < Br2 E. Ar < Ne < Br2 < Cl2 6. Which of the following molecules experience dipole-dipole forces? A. CCl4 B. H2S C. SO2 D. CO2 E. both SO2 and H2S 1 CHM-101-A Exam 4 December 5, 2006 Version 1 7. Which of the molecules in the figure has hydrogen bonding in the pure liquid state? CH3CH2OCH2CH3 CH3NH2 H2S A. B. C. D. E. II only I only II and III III only I and II 8. A solid substance has a high melting point, is hard, brittle, and conducts electricity when molten. This substance is probably a(n)________ solid. A. polar molecular B. nonpolar molecular C. metallic D. ionic E. network 9. Which of the following statements regarding the solution process is incorrect? A. Some of the hydrogen bonds among the water molecules must break. B. Hydration is the process whereby water molecules surround solute particles. C. In a sodium chloride solution, the ions interact with the water molecules through iondipole forces. D. When an ionic compound dissolves, the ionic bonds break. E. A hydrated cation is surrounded by the partially positive end of the water molecules. 10. When potassium nitrate is dissolved in water, the resulting solution feels cool to the touch. This means that: A. there is a decrease in entropy for the solution. B. hydrogen bonds must be broken, which is an exothermic process. C. the strength of attraction between the solute and solvent particles is greater than that of the attraction between the solute particles. D. the strength of attraction between the solute particles is greater than that of the attraction between the solute and solvent. E. the strength of attraction between the solute particles is equal to that of the attraction between the solute and solvent. 11. What will happen to a blood cell that is placed in pure water? A. The cell will shrink because there will be a net flow of water to the outside of the cell. B. Nothing will happen because the cell is impermeable. C. The cell will shrink because there will be a net flow of electrolytes to the outside of the cell. D. The cell will expand because there will be a net flow of water to the inside of the cell. E. The cell will expand because there will be a net flow of electrolytes to the inside of the cell. 2 CHM-101-A Exam 4 December 5, 2006 Version 1 12. What happens to the vapor pressure, boiling point, and freezing point of a liquid when a solute is dissolved in the liquid to form a solution? A. vapor pressure increases, boiling point decreases, and freezing point increases B. vapor pressure increases, boiling point increases, and freezing point increases C. vapor pressure decreases, boiling point increases, and freezing point decreases D. vapor pressure increases, boiling point decreases, and freezing point decreases E. vapor pressure decreases, boiling point decreases, and freezing point decreases 13. The images represent a solution of NaCl, a solution of glucose, and a more dilute solution of glucose. Rank the aqueous solutions in order of highest to lowest freezing point. A. B. C. D. E. II > I > III II > III > I I > II > III III > II > I III > I > II 14. The rate of a reaction can be increased by all of the following except: A. increasing the concentration of the reactants. B. increasing the surface area of the reactants. C. increasing the volume of the reaction vessel. D. increasing the temperature. E. adding a catalyst. 15. Which of the following statements regarding catalysts is incorrect? A. A catalyst increases the rate of a reaction by giving the reaction an alternate pathway with a lower activation energy. B. In a chemical reaction, the catalyst is shown on the reactant side of the equation. C. The shape of an active site on an enzyme is unique, allowing it to react with only one substrate. D. Enzymes act as catalysts in our bodies. E. Catalysts need not be present in large amounts because they are regenerated during the reaction. 3 CHM-101-A Exam 4 December 5, 2006 Version 1 16. If the following reaction is carried out in a sealed container: 2SO3(g) 2SO2(g) + O2(g) a state of equilibrium can be reached if the container initially contains: A. SO3 only. B. SO3, SO2, and O2. C. SO3 and O2 only. D. SO2 and O2 only. E. any of these combinations of reactants and products. 17. Select the correct equilibrium constant expression for the reaction: CH4(g) + 2H2S(g) CS2(g) + 4H2(g) A. K eq = [CS2 ][H 2 ] [CH 4 ][H 2S] [CS2 ][H 2 ]4 [CH 4 ][H 2S]2 [CH 4 ][H 2S] C. K eq = [CS2 ][H 2 ] D. Keq = [CS2][H2]4 - [CH4][H2S]2 E. Keq = [CS2][H2]4 + [CH4][H2S]2 B. K eq = 18. Consider the following system at equilibrium: CH4(g) + 2H2O(g) CO2(g) + 4H2(g) What change will cause the equilibrium to shift to form more CO2? A. add a catalyst B. decrease [H2O] C. decrease the volume of the reaction vessel D. decrease [H2] E. decrease [CH4] 19. Ethane, C2H6, can be formed by reacting acetylene, C2H2, with hydrogen gas as follows: C2H6(g) Exothermic C2H2(g) + H2(g) What change will be observed if the temperature of the reaction mixture at equilibrium were increased? A. The concentration of C2H6 will increase. B. The concentration of both C2H2 and H2 will increase. C. There will be no change in the equilibrium concentrations. D. The concentration of both C2H2 and H2 will decrease. E. The concentration of H2 only will decrease. 20. Select the two Brønsted-Lowry acids in the equation: HNO2(aq) + H2O(aq) NO2–(aq) + H3O+(aq) A. NO2– and H3O+ B. HNO2 and H2O C. H2O and H3O+ D. HNO2 and H3O+ E. HNO2 and NO2– 4 CHM-101-A Exam 4 December 5, 2006 Version 1 21. Select the pair that consists of an acid and its conjugate base in that order. A. CO32–/ CO22– B. CO32–/HCO3– C. H2CO3/HCO3– D. NH3/NH4+ E. HPO42–/H3PO4 22. Which of the following is the strongest acid? A. HCN, Ka = 6.2 × 10–10 B. HF, Ka = 6.3 × 10–4 C. HOCl, Ka = 4.0 × 10–8 D. CH3CO2H, Ka = 1.8 × 10–5 E. HCO2H, Ka = 1.8 × 10–4 23. Select the solution below that is the most acidic. A. [H3O+] = 1.0 × 10–10 M B. [H3O+] = 1.0 × 10–6 M C. [H3O+] = 1.0 × 10–8 M D. [H3O+] = 1.0 × 10–7 M E. [H3O+] = 1.0 × 10–4 M 24. Calculate the pH of a solution that has [H3O+] = 1.0 × 10–7M. A. pH = 1.00 B. pH = 14.00 C. pH = 7.00 D. pH = 6.00 E. pH = 8.00 25. Calculate the pH of a solution that has [OH–] = 1.0 × 10–6 M. A. pH = 7.00 B. pH = 14.00 C. pH = 1.00 D. pH = 6.00 E. pH = 8.00 5 CHM-101-A Exam 4 December 5, 2006 Version 1 Exam 4 Version 1 Key 1.A 2.A 3.C 4.E 5.A 6.E 7.A 8.D 9.E 10.D 11.D 12.C 13.E 14.C 15.B 16.E 17.B 18.D 19.B 20.D 21.C 22.B 23.E 24.C 25.E 1 CHM-101-A Exam 4 December 5, 2006 Version 2 1. Which of the following statements is correct? A. Since acetone (nail polish remover) evaporates more readily than water, one would assume that acetone has weaker intermolecular forces. B. A liquid which has a high boiling point has a higher vapor pressure at a given temperature than a liquid with a low boiling point. C. Evaporation is an exothermic process, since heat is given off when a substance vaporizes. D. Liquids boil at higher temperatures in the mountains due to the higher altitude. E. The phase change from solid to gas is exothermic. 2. Which of the following is not an attractive force that acts between the individual molecules of CH3OH? A. covalent bonds B. hydrogen-bonding forces C. London dispersion forces D. dipole-dipole forces E. none of these is correct 3. The physical properties of a substance that are influenced by the strength of intermolecular forces include all of the following except: A. boiling point. B. viscosity. C. melting point. D. vapor pressure. E. mass. 4. Which of the following substances is most likely to be a gas at room temperature and atmospheric pressure? A. Pb B. Ar C. C8H18 D. CCl4 E. I2 5. Rank the following substances in order of increasing boiling point: Cl2, Ar, Ne, Br2 A. Cl2 < Br2 < Ar < Ne B. Ne < Ar < Cl2 < Br2 C. Ar < Ne < Br2 < Cl2 D. Ne < Ar < Br2 < Cl2 E. Cl2 < Ar < Ne < Br2 6. Which of the following molecules experience dipole-dipole forces? A. H2S B. SO2 C. CO2 D. CCl4 E. both SO2 and H2S 1 CHM-101-A Exam 4 December 5, 2006 Version 2 7. Which of the molecules in the figure has hydrogen bonding in the pure liquid state? CH3CH2OCH2CH3 CH3NH2 H2S A. B. C. D. E. I only II and III II only I and II III only 8. A solid substance has a high melting point, is hard, brittle, and conducts electricity when molten. This substance is probably a(n)________ solid. A. nonpolar molecular B. polar molecular C. ionic D. metallic E. network 9. Which of the following statements regarding the solution process is incorrect? A. When an ionic compound dissolves, the ionic bonds break. B. Hydration is the process whereby water molecules surround solute particles. C. In a sodium chloride solution, the ions interact with the water molecules through iondipole forces. D. Some of the hydrogen bonds among the water molecules must break. E. A hydrated cation is surrounded by the partially positive end of the water molecules. 10. When potassium nitrate is dissolved in water, the resulting solution feels cool to the touch. This means that: A. there is a decrease in entropy for the solution. B. hydrogen bonds must be broken, which is an exothermic process. C. the strength of attraction between the solute particles is greater than that of the attraction between the solute and solvent. D. the strength of attraction between the solute particles is equal to that of the attraction between the solute and solvent. E. the strength of attraction between the solute and solvent particles is greater than that of the attraction between the solute particles. 11. What will happen to a blood cell that is placed in pure water? A. Nothing will happen because the cell is impermeable. B. The cell will shrink because there will be a net flow of water to the outside of the cell. C. The cell will expand because there will be a net flow of water to the inside of the cell. D. The cell will expand because there will be a net flow of electrolytes to the inside of the cell. E. The cell will shrink because there will be a net flow of electrolytes to the outside of the cell. 2 CHM-101-A Exam 4 December 5, 2006 Version 2 12. What happens to the vapor pressure, boiling point, and freezing point of a liquid when a solute is dissolved in the liquid to form a solution? A. vapor pressure decreases, boiling point increases, and freezing point decreases B. vapor pressure increases, boiling point decreases, and freezing point increases C. vapor pressure increases, boiling point decreases, and freezing point decreases D. vapor pressure increases, boiling point increases, and freezing point increases E. vapor pressure decreases, boiling point decreases, and freezing point decreases 13. The images represent a solution of NaCl, a solution of glucose, and a more dilute solution of glucose. Rank the aqueous solutions in order of highest to lowest freezing point. A. B. C. D. E. I > II > III II > III > I III > II > I II > I > III III > I > II 14. The rate of a reaction can be increased by all of the following except: A. increasing the volume of the reaction vessel. B. increasing the concentration of the reactants. C. increasing the surface area of the reactants. D. increasing the temperature. E. adding a catalyst. 15. Which of the following statements regarding catalysts is incorrect? A. Catalysts need not be present in large amounts because they are regenerated during the reaction. B. The shape of an active site on an enzyme is unique, allowing it to react with only one substrate. C. Enzymes act as catalysts in our bodies. D. In a chemical reaction, the catalyst is shown on the reactant side of the equation. E. A catalyst increases the rate of a reaction by giving the reaction an alternate pathway with a lower activation energy. 3 CHM-101-A Exam 4 December 5, 2006 Version 2 16. If the following reaction is carried out in a sealed container: 2SO3(g) 2SO2(g) + O2(g) a state of equilibrium can be reached if the container initially contains: A. SO2 and O2 only. B. SO3, SO2, and O2. C. SO3 only. D. SO3 and O2 only. E. any of these combinations of reactants and products. 17. Select the correct equilibrium constant expression for the reaction: CH4(g) + 2H2S(g) CS2(g) + 4H2(g) A. Keq = [CS2][H2]4 - [CH4][H2S]2 B. Keq = [CS2][H2]4 + [CH4][H2S]2 [CS2 ][H 2 ]4 C. K eq = [CH 4 ][H 2S]2 [CS2 ][H 2 ] D. K eq = [CH 4 ][H 2S] [CH 4 ][H 2S] E. K eq = [CS2 ][H 2 ] 18. Consider the following system at equilibrium: CH4(g) + 2H2O(g) CO2(g) + 4H2(g) What change will cause the equilibrium to shift to form more CO2? A. decrease [H2O] B. add a catalyst C. decrease [H2] D. decrease the volume of the reaction vessel E. decrease [CH4] 19. Ethane, C2H6, can be formed by reacting acetylene, C2H2, with hydrogen gas as follows: C2H2(g) + H2(g) C2H6(g) Exothermic What change will be observed if the temperature of the reaction mixture at equilibrium were increased? A. The concentration of C2H6 will increase. B. The concentration of both C2H2 and H2 will increase. C. There will be no change in the equilibrium concentrations. D. The concentration of both C2H2 and H2 will decrease. E. The concentration of H2 only will decrease. 20. Select the two Brønsted-Lowry acids in the equation: NO2–(aq) + H3O+(aq) HNO2(aq) + H2O(aq) A. HNO2 and H2O B. NO2– and H3O+ C. HNO2 and H3O+ D. HNO2 and NO2– E. H2O and H3O+ 4 CHM-101-A Exam 4 December 5, 2006 Version 2 21. Select the pair that consists of an acid and its conjugate base in that order. A. CO32–/ CO22– B. HPO42–/H3PO4 C. NH3/NH4+ D. CO32–/HCO3– E. H2CO3/HCO3– 22. Which of the following is the strongest acid? A. HF, Ka = 6.3 × 10–4 B. CH3CO2H, Ka = 1.8 × 10–5 C. HCO2H, Ka = 1.8 × 10–4 D. HCN, Ka = 6.2 × 10–10 E. HOCl, Ka = 4.0 × 10–8 23. Select the solution below that is the most acidic. A. [H3O+] = 1.0 × 10–6 M B. [H3O+] = 1.0 × 10–7 M C. [H3O+] = 1.0 × 10–4 M D. [H3O+] = 1.0 × 10–8 M E. [H3O+] = 1.0 × 10–10 M 24. Calculate the pH of a solution that has [H3O+] = 1.0 × 10–7M. A. pH = 1.00 B. pH = 6.00 C. pH = 14.00 D. pH = 7.00 E. pH = 8.00 25. Calculate the pH of a solution that has [OH–] = 1.0 × 10–6 M. A. pH = 1.00 B. pH = 14.00 C. pH = 6.00 D. pH = 7.00 E. pH = 8.00 5 CHM-101-A Exam 4 December 5, 2006 Version 2 Exam 4 Version 2 Key 1.A 2.A 3.E 4.B 5.B 6.E 7.C 8.C 9.E 10.C 11.C 12.A 13.E 14.A 15.D 16.E 17.C 18.C 19.B 20.C 21.E 22.A 23.C 24.D 25.E 1