Take Home Semester 2 Practice Test for Acc Chem MM 15-16 Thermochemistry 1. Determine ΔHrxn. 2SO2(g) + O2(g) 2SO3(g) a) 98.9 b) 98.9 c) 197.8 d) 197.8 ΔHf o SO2(g) 296.8 kj/mol SO3(g) 395.7 kj/mol O2(g) 0 2. The enthalpy of combustion of butane gas (C4H10) is 2878 kj/mol. Which statement is incorrect? a) ΔHf o (C4H10) = 2878 kj/mol b) Combustion of butane is an exothermic process. c) Butane releases heat as it burns. d) The energy of the reactants is higher than the energy of the products. 3. The entropy of the reaction: H2 (g) + Br2 (g) 2HBr (g) is. a) Increasing b) Decreasing c) Staying the same 4. If H is and S is, then a reaction will always be spontaneous. a) -, - b) +, + c) +, - d) -, + 5. When G is +, a reaction will be. a) Spontaneous b) Nonspontaneous Rates Use the graph to answer questions 6-8. 6. What letter shows the activation energy? a) A b) B c) C d) E 7. What letter shows the net energy change? a) B b) C c) D d) E 8. This reaction is a) Endothermic b) Exothermic.
9. A piece of steel wool heated in air (~20% oxygen) burns slowly, but when heated in pure oxygen, rapidly combusts producing a dazzling shower of sparks. This shows the effect of on rates. a) Temperature b) Concentration c) Nature of reactants d) Surface area 10. Storing foods and milk in a refrigerator helps to slow down reactions that ordinarily result in spoiling and souring. This shows the effect of on rates. a) Temperature b) Concentration c) Nature of reactants d) Surface area 11. Using the data provided, determine the rate law a) Rate = k [B] b) Rate = k [A] 2 c) Rate = k [B] 2 d) Rate = k [A] [B] Exp [A] [B] Initial Rate 1 0.30 M 0.20 M 0.60 M/s 2 0.10 M 0.30 M 0.067 M/s 3 0.10 M 0.20 M 0.067 M/s Equilibrium 12. Which of the following is NOT true for a completion reaction? a) Forms a gas or a precipitate b) Can reach equilibrium c) Represented by a d) Reaction eventually stops 13. Which of the following describes an equilibrium reaction? a) The reaction stops b) All reactants are consumed c) No product is forming d) Reactants and products are both being formed. 14. If the equilibrium concentrations of the reaction are found to be [A] = 0.015M, [B] = 2.0x10-4 M, and [C] = 3.0x10-9 M, the equilibrium constant, Keq, would be. A (g) + B (g) C (g) a) 5.0 b) 0.20 c) 1.0x10-3 d) 9.0x10-15 15. If the [A] is increased, how will the reaction respond to reestablish equilibrium? A (g) + B (g) C (g) a) Shift left, increasing [B] b) Shift right, increasing [C] c) No shift 16. If the temperature is increased, how will the reaction respond to reestablish equilibrium? A (g) + B (g) C (g) + heat a) Shift left, increasing [B] and [A] b) Shift right, increasing [C] c) No shift
17. What substance can be added to decrease the solubility of PbI2 (s)? PbI2 (s) Pb 2+ (aq) + 2I - (aq) a) NaCl (aq) b) PbI2 (s) c) PbSO4 (aq) d) AgNO3 (aq) 18. What is the Ksp of silver chloride with a molar solubility of 6.3 x 10-8 mol/l? a) 1.3 x 10-7 b) 6.3 x 10-8 c) 4.0 x 10-15 d) 1.0 x 10-21 Gases 19. A sample of helium gas is in a sealed, rigid container. What occurs as the temperature of the sample is increased? a) The mass of the sample decreases. b) The number of moles of gas increases. c) The volume of each atom decreases. d) The frequency of collisions between atoms increases. 20. The temperature of a sample of matter is a measure of the a) average kinetic energy of its particles b) average potential energy of its particles c) total kinetic energy of its particles d) total potential energy of its particles 21. The temperature in a propane tank increases, which causes the pressure to while the volume stays constant. a) Increase b) Decrease c) Stay the same 22. Properties that describe gases include. a) Compressible, high density, expands to fill container b) Expands to fill container, more dense than liquids, fixed shape c) Very low density, not compressible, fixed shape d) Compressible, expands to fill container, very low density 23. A piston in an engine compresses the gas into a smaller volume at a constant temperature. The pressure. a) Increase b) Decrease c) Stay the same 24. An oxygen sample has a volume of 4.50 L at 300. K and 1.05 atm. How many moles of oxygen does it contain? a) 0.192 mol b) 2.14 mol c) 5.20 mol d) 146 mol
25. Butane gas, C4H10, is collected over water at a 25 C. The total pressure is 762. mmhg. At 25 C, water vapor pressure is 17 mmhg. What is the partial pressure of the butane gas? a) 17 mmhg b) 745 mmhg c) 762 mmhg d) 779 mmhg 26. How many grams of oxygen gas are needed to react with 12.50 L of hydrogen gas at STP. 2 H2 (g) + O2 (g) 2 H2O (l) a) 4.464 g b) 8.929 g c) 17.86 g d) 4480. g Phase Diagrams 27. Which of the following pairs are both exothermic phase changes? a) melting, freezing b) condensation, vaporization c) sublimation, vaporization d) condensation, freezing Use the diagram to answer questions 11-12 28. At a temperature of 0 o C and 20.0 atm, what is the state of matter of CO2? a) Gas b) Liquid c) Solid 29. At a pressure of 40.0 atm, if you cooled CO2 from 20 o C to -20 o C, what phase change would you observe? a) Condensation b) Freezing c) Sublimation d) Vaporization Colligative Properties 30. Which type of substance produces more particles in solution? a) Ionic b) Covalent c) Metallic d) All produce the same number of particles
31. What is the relationship between colligative properties and electrolytes? a) If a substance is an electrolyte, it will change the colligative property more than if the substance is a nonelectrolyte. b) If a substance is a nonelectrolyte, it will change the colligative property more than if the substance is an electrolyte. c) There isn t a relationship. 32. What is the boiling point of a solution that contains 1.00 mole of potassium iodide, KI, in 1.00 kg of water? Kb = 0.512 o C/m a) 98.98 C b) 99.49 C c) 100.51 C d) 101.02 C 33. When salt is added to water, the freezing point of the solution is reduced. Which of the following explains why the freezing point is lowered? a) The ions form a layer at the top of the water making it harder freeze. b) The ions formed attract the water molecules to the bottom of the container making it harder to freeze. c) The ions formed create an exothermic reaction making it harder to freeze. d) The ions formed interfere with the hydrogen bonding between the water molecules making it harder to freeze. Solutions Use the graph to answer questions 34-35. 34. If 10 grams of substance KClO3 are dissolved in 100.0 g of water at 50 C, the solution will be a) Saturated b) Supersaturated c) Unsaturated 35. If 50 grams of substance KCl is placed into 100.0 g of water at 30 C and stirred, the solution will be. a) Unsaturated b) Saturated c) supersaturated 36. In a can of pop, CO2 is the and water is the. a) solute; solvent b) solvent; solute c) solution; solute d) solute; solution 37. The rule like dissolves like is used to predict solubility. Molecules must be alike in. a) State of Matter b) Reactivity c) Volume d) polarity
38. The solubility of a gas in a liquid as temperature increases. a) decreases b) doesn t change c) increases 39. Which of the following will increase the rate that a solute dissolves? a) Having large chunks b) Stirring the solution c) Cooling the solution d) all of the above 40. A 1.00 M solution of NaCl contains. a) 1 liter of solute per mol of solution b) 10.0 g of solute per liter of solution c) 1 mol of solute per liter of solution d) 1 mol of solute per mole of solution. 41. A 2.50 M solution of salt water is left in the lab without a lid. The concentration of the solution after 1 week in the lab without a lid most likely will be than the starting concentration. a) higher b) lower c) the same as 42. How many moles of solute are present in 25.0 ml of 2.00 M HCl? a) 0.0500 mol b) 0.0800 mol c) 2.00 mol d) 50.0 mol 43. A solution is prepared by dissolving 200.1 g of solid NaOH in enough water to make 851 ml of solution. What is the molarity? a) 0.00588M b) 4.78 M c) 5.88 M d) 235 M 44. How much water needs to be added to make 500. ml of a 0.25 M solution from a 6.5 M stock solution? a) 19 ml b) 481 ml c) 500 ml d) 519 ml Acids and Bases 45. What is the ph of a solution with a [H3O + ] = 1.65 x 10-5 a) 1.65 b) 4.78 c) 5.21 d) 9.22
Use the reaction to answer questions 46-47 CH3COOH + H2O CH3COO - + H3O + 46. Bronsted-Lowry acid? a) CH3COOH b) H2O c) CH3COO - d) H3O + 47. Which is the Bronsted-Lowry conjugate acid? a) CH3COOH b) H2O c) CH3COO - d) H3O + 48. What is the ph of a solution with a [OH - ] = 3.65 x 10-6 a) 3.65 b) 5.44 c) 8.56 d) 10.35 49. What is the molarity of an HCl solution if 50.0 ml is neutralized in a titration of 40.0mL of 0.400 M NaOH? NaOH + HCl NaCl + H2O a) 0.200M b) 0.280M c) 0.320M d) 0.500M 50. Which solution will light up a conductivity bulb brighter and why? a) 0.10 M HNO3 because it is a strong acid. b) 0.10 M HNO3 because it produces 5 particles in solution. c) 0.20 M HF because it has a higher molarity. d) Both solutions will have the same light bulb brightness. 51. Within acids and bases, what does strong mean? a) Strong means a substance has a high molarity. b) Strong means a substance has a powerful odor. c) Strong means a substance ionizes 100%. d) Strong means a substance is covalent.