Chapter 6 Test
22. A 2.05 g sample of a metal alloy is heated to 98.88°C. It is then dropped into 28.0 g of water in a coffee cup calorimeter. The water temperature rises from 19.73°C to 21.23°C. Calculate the specific heat of the alloy. The specific heat of water is 4.184 J/g·°C.
1.11 J/g∙°C
21. Calculate the amount of energy, in kJ, required to convert 175 grams of liquid water at 25.0°C to water vapor at 115°C. Specific heat of solid water = 2.09 J/g·°C Heat of vaporization of water = 40.7 kJ/mol Specific heat of liquid water = 4.184 J/g·°C Heat of melting water = 6.01 kJ/mol Specific heat of gaseous water = 1.84 J/g·°C
455 kJ
7. Consider the following two reactions: A → 2B ΔH°rxn = 456.7 kJ/mol A → C ΔH°rxn = -22.1 kJ/mol Determine the enthalpy change for the process: 2B → C A) -478.8 kJ/mol B) -434.6 kJ/mol C) 434.6 kJ/mol D) 478.8 kJ/mol
A) -478.8 kJ/mol
20. The enthalpy change, ΔH°, for the reaction given below is -336 kJ/mole. Calculate the heat released, in kilojoules, to the surroundings when 23 g of HCl is formed. CH4(g) + 3 Cl2(g) → CHCl3(l) + 3 HCl(g) A) 71 J B) 177 J C) 211 J D) 2600 J
A) 71 J
10. Substance A has a higher specific heat than substance B. With all other factors equal, which requires more energy to heat equal masses of A and B to the same temperature? A) Substance A B) Substance B C) Both require the same amount of heat D) The answer depends on the density of each substance
A) Substance A
1. Enthalpy is an expression for the A) total heat content of a system B) energy state of a system C) reaction rate D) activation energy
A) total heat content of a system
5. The condensation of water vapor actually A) warms the surroundings B) cools the surroundings C) sometimes warms and sometimes colds the surroundings, depending on the relative humidity at the time D) neither warms nor cools the surroundings
A) warms the surroundings
16. Given heat of formation data in the table below, calculate the enthalpy change (ΔH°rxn) for the reaction written below. A) -744.9 kJ B) -130.4 kJ C) -4219 kJ D) -4519 kJ Ca(OH)2 + 2 H3AsO4 → Ca(H2AsO4)2 + 2 H2O Substance ΔHf° (kJ/mol) Ca(OH)2 -986.6 H3AsO4 -900.4 Ca(H2AsO4)2 -2346 H2O -285.9
B) -130.4 kJ
18. Given the following reactions: 2 S(s) + 3 O2(g) → 2 SO3(g) ΔH = -790 kJ S(s) + O2(g) → SO2(g) ΔH = -297 kJ Find the enthalpy of the reaction in which sulfur dioxide is oxidized to sulfur trioxide as shown below. 2 SO2(g) + O2(g) → 2 SO3(g) A) -493 kJ B) -196 kJ C) -1380 kJ D) 1090 kJ
B) -196 kJ
13. The molar heat capacity of a compound with the formula C2H6SO is 88.0 J/mol·°C. The specific heat of this substance is _____ J/g·°C. A) 88.0 J/g·°C B) 1.13 J/g·°C C) 4.89 J/g·°C D) 6.88 · 103 J/g·°C
B) 1.13 J/g·°C
6. For which one of the following reactions is ΔH°rxn equal to the heat of formation of the product? A) N2(g) + 3 H2(g) → 2 NH3(g) B) 1/2 N2(g) + O2(g) → NO2(g) C) 6 C(s) + 6 H(g) → C6H6(l) D) P4(s) + 12 Br(l) → 4 PBr3(l)
B) 1/2 N2(g) + O2(g) → NO2(g)
11. The temperature of a 12.58 g sample of calcium carbonate (CaCO3(s)) increases from 23.6°C to 38.2°C. If the specific heat of calcium carbonate is 0.82 J/g·°C, how many joules of heat are absorbed? A) 5.0 J B) 151 J C) 410 J D) 7.5 J
B) 151 J
12. The change in internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings is _____ J. A) 10,155 J B) 5,155 J C) -5,155 J D) -10,155 J
C) -5,155 J
19. The value of enthalpy, ΔH°, for the reaction below is -186 kJ. H2(g) + Cl2(g) → 2 HCl(g) The value of the standard heat of formation, ΔHf°, for HCl(g) is _____ kJ/mol. A) -372 kJ/mol B) -127 kJ/mol C) -93.0 kJ/mol D) -186 kJ/mol
C) -93.0 kJ/mol
15. The enthalpy change under standard conditions is the enthalpy change when all reactants and products are at _____ pressure and a specific temperature. A) 780 mm Hg B) 1 Torr C) 1 atm D) 760 kilopascals
C) 1atm
2. Which of the following is a statement of the first law of thermodynamics? A) kinetic energy = Ek = 1/2 mv² B) ΔE = Efinal - Einitial C) Energy lost by the system must be gained by the surroundings D) 1 calorie = 4.184 joules (exactly)
C) Energy lost by the system must be gained by the surroundings
4. The addition of heat causes particles to _____ their average kinetic energy. A) lessen the effect of B) decrease C) increase D) stay the same
C) increase
17. The combustion of titanium with oxygen produces titanium dioxide. Ti(s) + O2(g) → TiO2(s) When 2.06 grams of titanium is combusted in a bomb calorimeter, the temperature of the calorimeter increases from 25.0°C to 91.6°C. Calculate the heat of reaction for the combustion of one mole of titanium metal. The heat capacity of the calorimeter is 9.84 kJ/°C. A) 14.3 kJ B) 19.6 kJ C) -318 kJ D) -1.52 x 10^4 kJ
D) -1.52 x 10^4 kJ
14. A sample of iron absorbs 67.5 J of heat, upon which the temperature of the sample increases from 21.5°C to 28.5°C. If the specific heat of iron is 0.450 J/g·°C, what is the mass (in grams) of the iron sample? A) 4.3 g B) 11 g C) 1100 g D) 21 g
D) 21 g
9. Which of the following statements is false? A) Enthalpy is a state function B) The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the enthalpy change for the reverse reaction. C) The enthalpy change for a reaction depends on the state of the reactants and products D) The enthalpy of a reaction is equal to the heat of a reaction at constant volume.
D) The enthalpy of a reaction is equal to the heat of a reaction at constant volume.
8. Which one of the following conditions would always result in an increase in the internal energy of a system? A) The system loses heat and does work on the surroundings. B) The system gains heat and does work on the surroundings. C) The system loses heat and has work done on it by the surroundings. D) The system gains heat and has work done on it by the surroundings.
D) The system gains heat and has work done on it by the surroundings.
3. For a given process at constant pressure, ΔHreaction of -100 kJ/mole. This indicates the reaction is A) endothermic B) unstable C) in need of a catalyst D) exothermic
D) exothermic
