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Question 1 Given the following thermochemical data at 25°C and 1 atm pressure, 3/2 O2(g) + 2B(s) →B2O3(s); ΔH° = –1264 kJ O3(g) + 2B(s) → B2O3 (s); ΔH° = –1406 kJ determine ΔH° for the following reaction at 25°C and 1 atm pressure. 3O2(g) <-> 2O3(g); ΔHo = ? A. –980 kJ/mol B. +284 kJ/mol C. +980 kJ/mol D. –2670 kJ/mol E. –284 kJ/mol Question 2 If q = 28 kJ and w = 85 kJ for a certain process, that process: A. requires a catalyst. B. is endothermic. C. occurs slowly. D. is exothermic. E. cannot occur. Question 3 In a certain experiment, 0.1000 mol of hydrogen gas reacted with 0.1000 mol of solid iodine at a constant 1 atm pressure, producing 0.2000 mol of solid hydrogen iodide and absorbing 5.272 kJ of heat in the process. Which of the following thermochemical equations correctly describes this experiment? A. H2(g) + I2(s) →2HI(s); ΔH° = –52.72 kJ B. H2(g) + I2(s) → 2HI(s); ΔH° = 5.272 kJ C. H2(g) + I2(s) → 2HI(s); ΔH° = –5.272 kJ D. H2(g) + I2(s) → 2HI(s); ΔH° = 10.54 kJ E. H2(g) + I2(s)→ 2HI(s); ΔH° = 52.72 kJ Question 4 What is the standard enthalpy of formation of MgCO3(s)? MgO(s) + CO2(g) → MgCO3(s); ΔH° = –100.7 kJ Substance ΔH°f (kJ/mol) MgO(s) –601.6 CO2(g) –393.5 A. 107.4 kJ B. –308.8 kJ C. –894.4 kJ D. –1095.8 kJ E. 894.4 kJ Question 5 Which of the following has a standard enthalpy of formation value of zero at 25°C? A. Cl2(g) B. Cl2(l) C. Cl(g) D. Cl(s) E. Cl2(s) Question 6 The specific heat capacity of copper is 0.384 J/g×°C. What is the molar specific heat capacity of this substance? The molar mass of copper is 63.54 g/mol. A. 2.60 J/mol×°C B. 24.4 J/mol×°C C. 0.00604 J/mol×°C D. 165 J/mol×°C E. 0.384 J/mol×°C Question 7 Which of the following statements is not true for an exothermic reaction? A. The products have a higher heat content than the reactants. B. The temperature of the reaction system increases. C. The temperature of the surroundings increases. D. Heat passes from the reaction system to the surroundings. E. The enthalpy change for the reaction is negative. Question 8 A 85.9-g piece of cobalt (s = 0.421 J/(g · °C)), initially at 263.1°C, is added to 116.2 g of a liquid, initially at 24.7°C, in an insulated container. The final temperature of the metal–liquid mixture at equilibrium is 50.8°C. What is the identity of the liquid? Neglect the heat capacity of the container. A. acetone (s = 2.15 J/(g · °C)) B. ethanol (s = 2.43 J/(g · °C)) C. water (s = 4.18 J/(g · °C)) D. methanol (s = 2.53 J/(g · °C)) E. hexane (s = 2.27 J/(g · °C)) Question 9 The internal energy of a substance is defined as: A. the potential energy of all particles which make up the substance. B. the kinetic energy of all particles which make up the substance. C. the sum of the potential and kinetic energy of all particles which make up the substance. D. the thermal energy of all particles which make up the substance. E. the chemical energy of all particles which make up the substance. Question 10 Which of the following statements is true concerning the decomposition of liquid water to form hydrogen gas and oxygen gas? 2H2O(l) → 2H2(g) + O2(g) A. ∆H is greater than ∆U because the pressure is constant. B. ∆H is less than ∆U because of the pressure–volume work done by the gaseous products. C. ∆H is less than ∆U because the atmosphere does pressure–volume work on the gaseous products. D. ∆H equals ∆U because both are state functions. E. ∆H is greater than ∆U because of the pressure–volume work done by the gaseous products. Question 11 Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of N,N-diethyl-m-toluamide, C12H17NO(l), the active ingredient in some insect repellents? A. 12C(l) + 17H(l) + N(l) + O(l) → C12H17NO(l) B. 12C(g) + 17H(g) + N(g) + O(g) → C12H17NO(g) C. 12C(s) + 17H(g) + N(g) + O(g) → C12H17NO(l) D. 12C(s) + 17/2 H2(g) + ½ N2(g) + ½ O2(g) → C12H17NO(l) E. 12C(g) + 17H(g) + N(g) + O(g) → C12H17NO(l) Question 12 From the following information, determine the enthalpy of formation of C2H4(g). ½ C2H4(g) → C(s) + H2(g); ΔH = –26.2 kJ A. –26.2 kJ/mol B. 26.2 kJ/mol C. 104.8 kJ/mol D. –52.4 kJ/mol E. 52.4 kJ/mol Question 13 If q = –91 kJ for a certain process, that process: A. requires a catalyst. B. is exothermic. C. occurs rapidly. D. is endothermic. E. cannot occur. Question 14 Given: Fe2O3(s) + 3CO(g) <-> 2Fe(s) + 3CO2(g); ∆H° = –26.8 kJ FeO(s) + CO(g)<-> Fe(s) + CO2(g); ∆H° = –16.5 kJ determine ∆H° for the following thermochemical equation. Fe2O3(s) + CO(g) <-> 2FeO(s) + CO2(g) A. 10.3 kJ B. 22.7 kJ C. –10.3 kJ D. 6.2 kJ E. –43.3 kJ Question 15 Which of the following statements about enthalpy is false? A. At constant pressure, the enthalpy change is equal to the heat absorbed or released. B. Enthalpy is an extensive property. C. Enthalpy is a state function. D. The change in enthalpy of a process cannot be negative. E. The SI unit of enthalpy is J. Question 16 What is the standard enthalpy change for the combustion of gaseous propylene, C3H6? C3H6(g) + 9/2 O2(g) →3CO2(g) + 3H2O(l) Substance ΔH°f (kJ/mol) C3H6(g) +20.4 CO2(g) –393.5 H2O(l) –285.8 A. +2017.5 kJ B. –2058.3 kJ C. –658.9 kJ D. –2017.5 kJ E. +2058.3 kJ Question 17 Which of the following statements is false concerning the reaction of hydrogen gas and oxygen gas given below? H2(g) + ½ O2(g)→H2O(l); ΔH = –285.8 kJ A. Per mole of O2, the change in enthalpy is –571.6 kJ. B. The value –571.6 kJ pertains to 1 mol of liquid water. C. If the equation is reversed, ΔH becomes +285.8 kJ. D. If the equation is multiplied by 2, ΔH becomes –571.6 kJ. E. For the reaction H2(g) + ½ O2(g) → H2O(g), ΔH is not equal to –285.8 kJ. Question 18 Consider the following changes at constant temperature and pressure: H2O(s) <-> H2O(l); ∆H1 H2O(l) <-> H2O(g); ∆H2 H2O(g) <-> H2O(s); ∆H3 Using Hess’s law, the sum ∆H1 +∆H2 + ∆H3 is A. greater than zero. B. sometimes greater than zero and sometimes less than zero. C. cannot be determined without numerical values for DH. D. less than zero. E. equal to zero. Question 19 In a bomb calorimeter, reactions are carried out A. at a constant volume. B. at 1 atm pressure and 0°C. C. at 1 atm pressure and 25°C. D. at a constant pressure and 25°C. E. at a constant pressure. Question 20 The enthalpy change at 1 atm of which reaction corresponds to the standard enthalpy of formation of solid potassium bromate, KBrO3? A. K(s) + Br(g) + 3O(g) → KBrO3(s) B. K(g) + Br(g) + 3O(g) → KBrO3(s) C. K(g) + ½ Br2(g) + 3/2 O2(g) → KBrO3(s) D. K(s) + ½ Br2(l) + 3/2 O2(g) → KBrO3(s) E. K(s) + ½ Br2(g) + 3/2 O2(g) → KBrO3(s) Question 21 Consider the following thermochemical equation: N2(g) + 2O2(g) → 2NO2(g); ΔH° = 66.2 kJ From this equation, we may conclude that 66.2 kJ is the quantity of heat that is A. gained from the surroundings when 1 mol of NO2 is formed at constant pressure. B. lost to the surroundings when 1 mol of NO2 is formed at constant pressure. C. gained from the surroundings when 2 mol of NO2 is formed at constant pressure. D. lost to the surroundings when 2 mol of NO2 is formed at constant pressure. E. lost to the surroundings when 1 mol of O2 is consumed at constant pressure. Question 22 A 100 g sample of each of the following metals is heated from 35°C to 45°C. Which metal absorbs the lowest amount of heat energy? Metal Specific Heat copper 0.385 J/(g · °C) magnesium 1.02 J/(g · °C) mercury 0.138 J/(g · °C) silver 0.237 J/(g · °C) lead 0.129 J/(g · °C) A. mercury B. silver C. copper D. lead E. magnesium Question 23 All of the following have a standard enthalpy of formation value of zero at 25°C except: A. C(s). B. Ne(g). C. Fe(s). D. F2(g). E. CO(g). Question 24 A 9.020-g sample of an unknown metal M is burned in the presence of excess oxygen, producing the oxide M2O3(s) and liberating 191.5 kJ of heat at constant pressure. What is the identity of the metal? 4M(s) + 3O2(g) → 2M2O3(s) Substance ΔH°f (kJ/mol) Yb2O3(s) –1814.6 Tb2O3(s) –1865.2 Sm2O3(s) –1823.0 Sc2O3(s) –1908.8 Y2O3(s) –1905.3 A. Sm B. Sc C. Yb D. Y E. Tb Question 25 What is the standard enthalpy change for the following reaction? 3CH4(g) + 4O3(g)→ 3CO2(g) + 6H2O(g) Substance ΔH°f (kJ/mol) CH4(g) –74.87 O3(g) +142.7 CO2(g) –393.5 H2O(g) –241.8 A. –2285.1 kJ B. –2977.5 kJ C. +2977.5 kJ D. +2285.1 kJ E. –3426.5 kJ Question 26 Which of the following is an endothermic process? A. work is done by the system on the surroundings B. heat energy flows from the system to the surroundings C. work is done on the system by the surroundings D. heat energy is evolved by the system E. none of the above Question 27 Which of the following processes will result in the lowest final temperature of the metal–water mixture at equilibrium? A. the addition of 100 g of cobalt (s = 0.418 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container B. the addition of 100 g of copper (s = 0.385 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container C. the addition of 100 g of gold (s = 0.129 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container D. the addition of 100 g of silver (s = 0.237 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container E. the addition of 100 g of chromium (s = 0.447 J/(g · °C)) at 95°C to 100 mL of water at 25°C in an insulated container Question 28 The energy associated with the separation of two electrical charges is called _____. A. potential energy B. temperature C. internal energy D. heat E. kinetic energy Question 29 Which of the following reactions corresponds to the thermochemical equation for the standard enthalpy of formation of solid lead (II) nitrate? A. Pb2+(aq) + 2NO3 – (aq) → Pb(NO3)2(s) B. Pb(OH)2(s) + 2HNO3(aq) → Pb(NO3)2(s) + 2H2O(l) C. Pb(s) + N2(g) + 3O2(g) → Pb(NO3)2(s) D. Pb(s) + 2HNO3(aq)→ Pb(NO3)2(s) + H2(g) E. Pb(s) + 2N(g) + 6O(g) → Pb(NO3)2(s) Question 30 What quantity, in moles, of hydrogen is consumed when 676.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)? H2(g) + ½ O2(g) → H2O(l); ΔH° = –285.8 kJ A. 2.368 mol B. 1.184 mol C. 0.4223 mol D. 3.368 mol E. 1.368 mol