Kinetics and Thermodynamics of Reactions

1. Under which temperature conditions will the following reaction be spontaneous?
A(aq)+B(aq) C(s)+D(aq) ΔH°=-34.0kJ/mol
ΔS° = -57.0 J/mol•K
A) above 273°C
B) below 323°C
C) above 552°C
D) below 705°C
E) At all temperatures.

2. What is the value of ΔG° (in kJ/mol) for this reaction at 25°C?
A (g) B (g) ΔH° = -42.4 kJ/mol ΔS°= -56 J/mol•K
A) -136
B) +236
C) -26
D) -59
E) none of the above

3. Consider a pure, crystalline solid being heated from absolute zero to some very high temperature. Which one of the following processes produces the greatest increase in the entropy of the substance?
A) Melting the solid
B) Heating the liquid
C) Heating the gas
D) Heating the solid
E) Boiling the liquid

4. The equilibrium constant for a reaction is 0.50 at 30°C. What is the value of ΔG° (kJ/mol) at this temperature?
A) -4.1
B) 4.1
C) 1.4 × 102
D) 1.7
E) More information is needed.

5. The equilibrium constant for the following reaction is 5.0 × 108 at 25°C.
N2 (g) + 3H2 (g) 2NH3 (g) The value of ΔG° for this reaction is __________ kJ/mol.
A) -4.2
B) -22
C) 22
D) -50
E) -25

6. Given the thermodynamic data in the table below, calculate the equilibrium constant for the reaction:
2SO2 (g) + O2 ➝ (g) 2SO3 (g)
Substance ΔHf° (kJ/mol) ΔS° (J/mol ・ K)
SO2 (g) - 297 249 O2 (g) 0 205 SO3 (g) -395 256

A) 3.82 × 1023
B) 1.06
C) 1.95
D) 32 × 1024
E) More data are needed.

7. ΔS will be positive for which of the following reactions?
I. BaF2 (s) Ba2+ (aq) + 2F- (aq)
II. CO2 (g) CO2 (s)
III. 2 NO2 (g) N2O4 (g)
IV.2 NH3 (g) N2 (g)+H2(g)
V.2H2 (g) + O2 (g) 2 H2O (g)
A) I and II
B) II and III
C) I and IV
D) IV and V
E) III and V

8. Which of the following reactions have a decrease in entropy?
I. H2O (l) H2O (g)
II.2 H2 (g) + O2 (g) 2 H2O (g)
III.MgO (s) + CO2 (g) MgCO3 (g)
IV.PCl5 (s) PCl3 (l) + Cl2 (g)
A) I and II
B) II and III
C) III and IV
D) I and III.
E) II and IV.

9. The equilibrium constant for a certain reaction is 0.705 at 298 K and 0.321 at 400 K. Which statement is correct?

A) The equilibrium constant cannot become smaller if the temperature is increased.
B) The reaction is endothermic.
C) The reaction is not spontaneous at any temperature if the standard entropy of reaction is negative.
D) The reaction is not spontaneous at any temperature if the standard entropy of reaction is positive.
E) The reaction is spontaneous at all temperatures if the standard entropy of reaction is positive.

10. For the following reaction:
Ag2O (s) Ag (s) + ½O2 (g)
H°f(kJ / K . mole) -31 0 0
S°(J / K . mole) 121.3 42.6 205.1
Calculate Kp at 25 °C.
A) 2.22 x 10-3
B) 2.22 x 10-2
C) 1.09 x 10-2
D) 4.41 x 10-1

11. Calculate the entropy change (J/mole.K) of the reaction. The molar entropies [S] are given in brackets after each substance.
2C2H2 (g) [200.8] + 5 O2 (g) [205.0] 4CO2 (g) [213.6] + 2H2O (l) [69.91]
A) -432.4
B) -122.3
C) 122.3
D) 432.4
E) 689.3

12. Calculate G (kJ/mol) for the reaction using the listed [ Gºf values]:
P2 (g) [103.7] + O2 (g) + 3Cl2 (g) 2POCl3 (g) [-502.5]
A) 1,109
B) -1,005
C) -606.2
D) 606.2
E) -1109

13. For the following reaction:
Ag2O (s) Ag (s) + ½O2 (g)
H°f (kJ / K . mole) -31 0 0
S° (J / K . mole) 121.3 42.6 205.1
Calculate the temperature (°C) where Kp = 1.
A) 152
B) 194
C) 222
D) 367

14. In glycolysis, the hydrolysis of phosphoenol pyruvate is thermodynamically driven by the highly exergonic enol-to-keto conversion of pyruvate. From the two half reactions shown below, what is the G° (kJ/mol) of the overall reaction?
Half reactions:
a. phosphoenol pyruvate + H2O enol pyruvate + HPO42- G° = -16 kJ/mol
b. keto pyruvate enol pyruvate G° = 49.5 kJ/mol
Overall reaction: phosphoenolpyruvate + + H2O keto pyruvate + HPO42-
A) 61.9
B) 29.9
C) -29.9
D) -61.9
E) 123.8

15. For the following reaction:CO (g) + 2 H2 (g) CH3OH (g)What are the units for Kp?

A) No units
B) atm.
C) atm-1
D) atm-2

16. Which one of the following cannot be determined using thermodynamics?

A) the direction of a spontaneous reaction
B) the temperature at which a reaction will be spontaneous
C) the extent of a reaction
D) the rate of a reaction
E) the value of the equilibrium constant.

17. An exothermic chemical reaction in which 2 moles of gaseous products are formed from 3 moles of gaseous reactants is favored by:

A) increasing both temperature and pressure.
B) increasing temperature and decreasing pressure.
C) decreasing both temperature and pressure.
D) decreasing temperature and increasing pressure.
E) none of the above changes.

18. Which of the following statements is true when you consider the following reaction:
A + B C + D?
A) If ΔH<0 and ΔS<0, then the reaction is product-favored at all temperatures.
B) If ΔH<0 and ΔS<0, then the reaction is never product-favored at any temperature.
C) If ΔH<0 and ΔS<0, then the reaction is product-favored at high temperatures but not at low temperatures.
D) If ΔH<0 and ΔS<0, then the reaction is product-favored at low temperatures but not at high temperatures.

19. Which of the following statements is false?

A) For a reaction at equilibrium, ΔG = 0.
B) All reactions in which the entropy of the universe increases are product-favored.
C) All reactions in which the entropy of the system increases are product-favored.
D) Some reactions that are product-favored at room temperature may not be product-favored at higher temperatures.
E) It is possible for a reactant-favored process to proceed to the product side, but only if it is continuously fueled by some other source of free energy, such that the combined
F)

20. Which of the following statements is true regarding the impact of additional chemicals on the solubility of a saturated solution of CaCO3?

A) CaCl2 will decrease its solubility; NaOH will increase its solubility.
B) HCl will decrease its solubility; CaCl2 will increase its solubility.
C) CaCl2 will decrease its solubility; HCl will increase its solubility.
D) NaCl will decrease its solubility; HCl will increase its solubility.