Thermochemistry and Thermodynamics. What is the standard heat of formation of methane, H f CH 4 (g), as calculated from the data above?

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Blake Greer
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1 Thermochemistry and Thermodynamics 38% 1. H 4 (g) + 2 O 2 (g) O 2 (g) + 2 H 2 O(l); = kj H f H 2 O(l) = kj / mole H f O 2 (g) = kj / mole What is the standard heat of formation of methane, H f H 4 (g), as calculated from the data above? (A) kj/mole (B) kj/mole () kj/mole (D) 75.8 kj/mole (E) kj/mole 36% A 16% 2. A cube of ice is added to some hot water in a rigid, insulated container, which is then sealed. There is no heat exchange with the surroundings. What has happened to the total energy and the total entropy when the system reaches equilibrium? Energy Entropy (A) Remains constant Remains constant (B) Remains constant Decreases () Remains constant Increases (D) Decreases Increases (E) Increases Decreases 3. NH 3 (g) + 2 H 4 (g) + 5/2 O 2 (g) H 2 NH 2 OOH(s) + 3 H 2 O(l) At constant temperature, H, the change in enthalpy for the reaction above is approximately equal to (A) E - (11/2)RT (B) E - (7/2)RT () E + RT (D) E + (7/2)RT (E) E (11/2)RT

2 D 58% D 49% 54% E 26% 4. Which of the following is probably true for a solid solute with a highly endothermic heat of solution when dissolved in water? (A) The solid has a low lattice energy. (B) As the solute dissolves, the temperature of the solution increases. () The resulting solution is ideal. (D) The solid is more soluble at higher temperatures. (E) the solid has a high energy of hydration. 5. Which of the following reactions has the largest positive value of S per mole of l 2 (A) H 2 (g) + l 2 (g) 2 Hl(g) (B) l 2 (g) + 1/2 O 2 (g) l 2 O(g) () Mg(s) + l 2 (g) Mgl 2 (s) (D) 2 NH 4 l(s) N 2 (g) + 4 H 2 (g) + l 2 (g) (E) l 2 (g) 2 l(g) 6. Which of the following must be true for a reaction that proceeds spontaneously from initial standard state conditions? (A) G > 0 and K eq > 1 (B) G > 0 and K eq < 1 () G < 0 and K eq > 1 (D) G < 0 and K eq < 1 (E) G = 0 and K eq = 1 7. H 2 O(s) H 2 O(l) When ice melts at its normal melting point, K and 1 atmosphere, which of the following is true for the process shown above? (A) H < 0, S > 0, V > 0 (B) H < 0, S < 0, V > 0 () H > 0, S < 0, V < 0 (D) H > 0, S > 0, V > 0 (E) H > 0, S > 0, V < 0

3 A 65% 8. Which of the following is a graph that describes the pathway of reaction that is endothermic and has high activation energy? (A) (B) () (D) (E)

4 D 74% 9. H 2 (g) + 1/2 O 2 (g) H 2 O(l) H = x 2 Na(s) + 1/2 O 2 (g) Na 2 O(s) H = y Na(s) + 1/2 O 2 (g) + 1/2 H 2 (g) NaOH(s) H = z Based on the information above, what is the standard enthalpy change for the following reaction? (A) x + y + z (B) x + y - z () x + y - 2z (D) 2z - x - y (E) z - x - y Na 2 O(s) + H 2 O(l) 2 NaOH(s) D 54% 10. For which of the following processes would S have a negative value? I. 2 Fe 2 O 3 (s) 4 Fe(s) + 3 O 2 (g) II. Mg OH Mg(OH) 2 (s) III. H 2 (g) + 2 H 4 (g) 2 H 6 (g) (A) I only (B) I and II only () I and III only (D) II and III only (E) I, II, and III

5 31% 11. N 2 (g) + 3 H 2 (g) 2 NH 3 (g) The reaction indicated above is thermodynamically spontaneous at 298 K, but becomes nonspontaneous at higher temperatures. Which of the following is true at 298 K? (A) G, H, and S are all positive. (B) G, H, and S are all negative. () G and H are negative, but S is positive. (D) G and S are negative, but H is positive. (E) G and H are positive, but S is negative. B 24% 12. I 2 (g) + 3 l 2 (g) 2 Il 3 (g) According to the data in the table below, what is the value of H for the reaction represented above? Bond Average Bond Energy (kilojoules / mole) I I 150 l l 240 I l 210 (A) kj (B) kj () kj (D) kj (E) + 1,260 kj Questions refer to the following types of energy. [loosely thermo!] 74% E 48% (A) Activation energy (B) Free energy () Ionization energy (D) Kinetic energy (E) Lattice energy 13. The energy required to convert a ground-state atom in the gas phase to a gaseous positive ion 14. The energy change that occurs in the conversion of an ionic solid to widely separated gaseous ions

6 B 42% A 71% 73% E 68% 15. The energy in a chemical or physical change that is available to do useful work 16. The energy required to form the transition state in a chemical reaction 17. Which of the following best describes the role of the spark from the spark plug in an automobile engine? (A) The spark decreases the energy of activation for the slow step. (B) The spark increases the concentration of the volatile reactant. () The spark supplies some of the energy of activation for the combustion reaction. (D) The spark provides a more favorable activated complex for the combustion reaction. (E) The spark provides the heat of vaporization for the volatile hydrocarbon. 18. Of the following reaction, which involves the largest decrease in entropy? (A) ao 3 (s) ao(s) + O 2 (g) (B) 2 O(g) + O 2 (g) 2 O 2 (g) () Pb(NO 3 ) 3 (s) + 2 KI(s) PbI 2 (s)+ 2 KNO 3 (s) (D) 3 H 8 (g) + O 2 (g) 3 O 2 (g) + 4 H 2 O(g) (E) 4 La(s) + 3 O 2 (g) 2 La 2 O 3 (s)

7 E 31% H 4 (g) + 3 O 2 (g) 2 O 2 (g) + 2 H 2 O(g) For the reaction of ethylene represented above, H is - 1,323 kj. What is the value of H if the combustion produced liquid water H 2 O(l), rather than water vapor H 2 O(g)? ( H for the phase change H 2 O(g) H 2 O(l) is +44 kj mol 1.) A) -1,235 kj B) -1,279 kj ) -1,323 kj D) -1,367 kj E) -1,411 kj A 31% 20. When solid ammonium chloride, NH 4 l(s) is added to water at 25, it dissolves and the temperature of the solution decreases. Which of the following is true for the values of H and S for the dissolving process? H S A) Postive Positive B) Positive Negative ) Positive Equal to zero D) Negative Positive E) Negative Negative

AP Chemistry Chapter 16 Assignment. Part I Multiple Choice

Page 1 of 7 AP Chemistry Chapter 16 Assignment Part I Multiple Choice 1984 47. CH 4 (g) + 2 O 2 (g) CO 2 (g) + 2 H 2 O(l) H = 889.1 kj H f H 2 O(l) = 285.8 kj mol 1 H f CO 2 (g) = 393.3 kj mol 1 What is