Exam 1A 1) The molar solubility of a salt M 2 X 3 is 1.9 10 3 M. (M is the cation and X is the anion.) What is the value of Ksp for this salt? a) 1.5E-13 b) 2.7E-12 c) 2.5E-14 d) 8.9E-13 e) 3.8E-3 2) What is the change in the internal energy (in J) of a system that releases 2500 J of heat and does 7655 J of work on the surroundings? a) 10,155 b) 5,155 c) 1.91 10 7 d) 10,155 e) 5,155 3) E is always negative when a system, a) absorbs heat and does work b) gives off heat and does work c) absorbs heat and has work done on it d) gives off heat and has work done on it e) none of these is always negative Questions 4-5 use the following information: Benzene burns in air according to the following reaction. 2 C 6 H 6 (l) + 15 O 2 (g) 12 CO 2 (g) + 6 H 2 O(l) The standard heats of formation (kj/mol) are: H 0 f (C 6 H 6 (l)) = 49.03, H 0 f (O 2 (g)) = 0, H 0 f (CO 2 (g) ) = 393.51, H 0 f (H 2 O(l)) = 285.83 4) Calculate the H 0 rxn in kj for this reaction. a) 6339 b) 5106 c) 775 d) 6535 e) 2909 5) Considering the H 0 just calculated, we conclude that the combustion of benzene in air is a) favored by enthalpy and by entropy b) favored by enthalpy only c) favored by entropy only d) is not favored by either enthalpy or entropy 6) Given the reactions, 1) N 2 (g) + O 2 (g) 2 NO(g) H = 180.7 kj 2) 2 NO(g) + O 2 (g) 2 NO 2 (g) H = 113.1 kj Find the H for the related reaction, 2 NO 2 (g) 2 O 2 (g) + N 2 (g) a) 67.6 b) 475 c) 67.6 d) 475 e) 45.5 7) Which one of the following is not true regarding enthalpy? a) The change in enthalpy is positive for a process that absorbs heat. b) Enthalpy is a state function c) The enthalpy of a system can be measured. d) Enthalpy is an extensive property. e) A change in enthalpy is measured at constant pressure. 8) A compound is warmed to its freezing point, X(s) X(l). The addition of more heat at the freezing point will a) continue to raise the temperature as melting occurs b) continue to raise the temperature as kinetic energy is increased c) continue to raise the temperature as entropy is increased
Chemistry 114 Exam 1A 1 d) increase the kinetic energy of the substance but not raise the temperature until melting is complete e) increase H rxn but not increase the temperature until melting is complete This information is for problems 9-10: A quantity of ice is mixed with a quantity of hot water in a sealed, rigid, insulated container. The insulation prevents any heat exchange between the ice-water mixture and the surroundings. The contents of the container soon reach equilibrium. 9) The total energy of the system 10) The total entropy of the system 11) The following reaction was demonstrated in class (298 K): Ba(OH) 2 8H 2 O (s) + 2 NH 4 SCN(s) Ba 2+ (aq) + 2 SCN (aq) + 2 NH 3 (g) + 10 H 2 O(l) We saw that a solution was formed and there was a distinct odor of ammonia gas. The beaker containing the solution froze to a wet wooden board. From this we conclude that the signs of G, S, and H are a) negative, negative, negative b) negative, positive, negative c) positive, positive, negative d) positive, positive, positive e) negative, positive, positive 12) Super-heated steam was generated in class. Which of the following statements is not true? a) It spontaneously condenses on a cold beaker b) Its molecules have greater entropy than molecules at normal boiling point c) It can cause paper to burn d) It reversibly condenses to water at 25 C e) Its molecules have greater kinetic energy than those at 100 C. 13) The normal boiling point of a compound is 38.5 C. Its normal freezing point is 50.0 C. Which of the following statements is correct? a) Its (the compound s) vapor undergoes spontaneous, irreversible condensation at 38.5 C b) Its vapor undergoes spontaneous, irreversible evaporation at 38.5 C c) Its vapor undergoes spontaneous, irreversible condensation at 40.0 C d) Its solid undergoes spontaneous and irreversible melting at 58.5 C e) Its liquid undergoes spontaneous and irreversible freezing at 50.0 C 14) Which of the following is an exothermic process? a) ice melting b) water evaporating c) boiling soup d) condensation of water vapor e) a drop in temperature when a chemical reaction takes place 15) The solubility of Cu(OH) 2 in water is increased by the addition of which of the following? 1) NaOH 2) HNO 3 3) 0.10 M CuCl 2 4) increasing the ph of the solution 5) Cu(OH) 2 a) only 1 b) only 2 c) only 3 d) 3&5 e) 1&4 16) For the reaction, A(l) + 2D(g) 3 X(G) + Z(s), G 0 = 512 kj/mol The equilibrium mixture a) will consist almost exclusively of A & D b) will consist almost exclusively of A & Z c) will consist almost exclusively of X & Z d) will consist with significant amounts of A, D, X, & Z e) is predictable only when one knows T and H 0
Chemistry 114 Exam 1A 2 17) Which of the following is in its standard state? a) H 2 O(g) b) Hg(s) c) Fe(l) d) N 2 (g) e) SiO 2 (g) 18) Estimate the normal boiling point ( C) of Br 2 given the information: H 0 f S 0 f Br 2 (g) 30.71 kj/mol 245.3 J/mol K Br 2 (l) 0 152.3 a) 31 b) 330 c) 57 d) 133 e) 273 19) Find G 0 in kj for the reaction below if the equilibrium constant is 5.0 10 8 at 298 K. N 2 (g) + 3 H 2 (g) 2 NH 3 (g) a) 50 b) 4.2 c) 25 d) 22 e) 22 20) A piece of metal at 30 C is put into 100-mL of water at 83.5 C. Which of the following temperatures ( C) is a reasonable final temperature for this system? a) 83.1 b) 25 c) 29.5 d) we cannot predict this without knowing the masses e) we cannot predict this without knowing both masses and the specific heat of the metal. Exam 1B 1) E is always negative when a system, a) absorbs heat and does work b) absorbs heat and has work done on it c) gives off heat and does work d) gives off heat and has work done on it e) none of these is always negative 2) Which one of the following is not true regarding enthalpy? a) Enthalpy is a state function b) The enthalpy of a system can be measured. c) Enthalpy is an extensive property. d) The change in enthalpy is positive for a process that absorbs heat. e) A change in enthalpy is measured at constant pressure. 3) The normal boiling point of a compound is 38.5 C. Its normal freezing point is 50.0 C. Which of the following statements is correct? a) Its (the compound s) vapor undergoes spontaneous, irreversible condensation at 38.5 C b) Its vapor undergoes spontaneous, irreversible evaporation at 38.5 C c) Its vapor undergoes spontaneous, irreversible condensation at 40.0 C d) Its solid undergoes spontaneous and irreversible melting at 58.5 C e) Its liquid undergoes spontaneous and irreversible freezing at 49.5 C This information is for problems 4-5: A quantity of ice is mixed with a quantity of hot water in a sealed, rigid, insulated container. The insulation prevents any heat exchange between the ice-water mixture and the surroundings. The contents of the container soon reach equilibrium.
Chemistry 114 Exam 1A 3 4) The total entropy of the system 5) The total energy of the system Questions 6-7 use the following information: Benzene burns in air according to the following reaction. 2 C 6 H 6 (l) + 15 O 2 (g) 12 CO 2 (g) + 6 H 2 O(l) The standard heats of formation (kj/mol) are: H 0 f (C 6 H 6 (l)) = 49.03, H 0 f (O 2 (g)) = 0, H 0 f (CO 2 (g) ) = 393.51, H 0 f (H 2 O(l)) = 285.83 6) Calculate the H 0 rxn in kj for this reaction. a) 6339 b) 5106 c) 775 d) 6535 e) 2909 7) Considering the H 0 just calculated, we conclude that the combustion of benzene in air is a) favored by enthalpy and by entropy b) favored by enthalpy only c) favored by entropy only d) is not favored by either enthalpy or entropy 8) What is the change in the internal energy (in J) of a system that releases 2500 J of heat and does 7655 J of work on the surroundings? a) 10,155 b) 5,155 c) 1.91 10 7 d) 10,155 e) 5,155 9) The molar solubility of a salt M 2 X 3 is 1.9 10 3 M. (M is the cation and X is the anion.) What is the value of Ksp for this salt? a) 1.5E-13 b) 2.7E-12 c) 2.5E-14 d) 8.9E-13 e) 3.8E-3 10) Given the reactions, 1) N 2 (g) + O 2 (g) 2 NO(g) H = 180.7 kj 2) 2 NO(g) + O 2 (g) 2 NO 2 (g) H = 113.1 kj Find the H for the related reaction, 2 NO 2 (g) 2 O 2 (g) + N 2 (g) a) 67.6 b) 475 c) 67.6 d) 475 e) 45.5 11) The solubility of Cu(OH) 2 in water is increased by the addition of which of the following? 1) HNO 3 2) NaOH 3) 0.10 M CuCl 2 4) increasing the ph of the solution 5) Cu(OH) 2 a) only 1 b) only 2 c) only 3 d) 3&5 e) 1&4 12) Which of the following is an exothermic process? a) ice melting b) condensation of water vapor c) boiling soup d) water evaporating 13) Super-heated steam was generated in class. Which of the following statements is not true? f) It reversibly condenses to water at 25 C g) It spontaneously condenses on a cold beaker h) Its molecules have greater entropy than molecules at normal boiling point i) It can cause paper to burn j) Its molecules have greater kinetic energy than those at 100 C. 14) Which of the following is in its standard state?
Chemistry 114 Exam 1A 4 a) H 2 O(g) b) Hg(s) c) N 2 (g) d) Fe(l) e) SiO 2 (s) 15) The following reaction was demonstrated in class (298 K): Ba(OH) 2 8H 2 O (s) + 2 NH 4 SCN(s) Ba 2+ (aq) + 2 SCN (aq) + 2 NH 3 (g) + 10 H 2 O(l) We saw that a solution was formed and there was a distinct odor of ammonia gas. The beaker containing the solution froze to a wet wooden board. From this we conclude that the signs of G, S, and H are a) negative, negative, negative b) negative, positive, positive c) positive, positive, negative f) positive, positive, positive e) negative, positive, negative. 16) A compound is warmed to its freezing point, X(s) X(l). The addition of more heat at the freezing point will a) continue to raise the temperature as melting occurs b) continue to raise the temperature as kinetic energy is increased c) continue to raise the temperature as entropy is increased d) increase the kinetic energy of the substance but not raise the temperature until melting is complete e) increase H rxn but not increase the temperature until melting is complete 17) Estimate the normal boiling point ( C) of Br 2 given the information: H 0 f S 0 f Br 2 (g) 30.71 kj/mol 245.3 J/mol K Br 2 (l) 0 152.3 a) 57 b) 330 c) 31 d) 133 e) 273 21) A piece of metal at 30 C is put into 100-mL of water at 83.5 C. Which of the following temperatures ( C) is a reasonable final temperature for this system? a) 25 b) 83.1 c) 29.5 d) we cannot predict this without knowing the masses e) we cannot this without knowing the masses and the specific heat of the metal 19) For the reaction, A(l) + 2D(g) 3 X(G) + Z(s), G 0 = 512 kj/mol The equilibrium mixture a) will consist almost exclusively of X & Z b) will consist almost exclusively of A & Z c) will consist almost exclusively of A & D d) will consist with significant amounts of A, D, X, & Z e) is predictable only when one knows T and H 0 20) Find G 0 in kj for the reaction below if the equilibrium constant is 5.0 10 8 at 298 K. N 2 (g) + 3 H 2 (g) 2 NH 3 (g) a) 50 b) 4.2 c) 22 d) 50 e) 22
Chemistry 114 Exam 1A 5