AP Chemistry Thermodynamics Review – Flashcards

The combustionof acetylene in the presence of excess oxygen yields carbon dioxide and water: 2 C₂H₂ (g) + 5 O₂ (g) → 4 CO₂ (g) + 2 H₂O (l) The value of ΔS° for this reaction is___________J/K.

The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, 2 S (s, rhombic) + 3 O₂ (g) → 2 SO₃ (g) is___________kJ/mol.

The normal boiling point of methanol is 64.7 °C and the molar enthalpy of vaporization is 71.8 kJ/mol. The value of ΔS when 2.15 mol of CH₃OH (l) vaporizes is___________J/K.

The equilibrium constant for a reaction is 0.48 at 25 °C. What is the value of ΔG° (kJ/mol) at this temperature?

Consider the reaction: FeO (s) + Fe (s) + O₂ (g) → Fe₂O₃ (s) Given the following thermodynamic data at 298.15 °K: FeO (s): ΔHf° = -271.9, S° = 60.75 Fe (s): ΔHf° = 0, S° = 27.15 O₂ (g): ΔHf° = 0, S° = 205 Fe₂O₃ (s): ΔHf° = -822.16, S° = 89.96

A reaction that is spontaneous as written___________. A) is very rapid B) will proceed without outside intervention C) is also spontaneous in the reverse direction D) has an equilibrium position that lies far to the left E) is very slow

Of the following, only___________is not a state function. A) S B) H C) q D) E E) T

Which of the following is always positive when a spontaneous process occurs? A) ΔSsystem B) ΔSsurroundings C) ΔSuniverse D) ΔHuniverse E) ΔHsurroundings

The second law of thermodynamics states that A) ΔE = q + w B) ΔH°rxn = ΣnΔH°f (products) - ΣmΔH°f (reactants) C) for any spontaneous process, the entropy of the universe increases] D) the entropy of a pure crystalline substance is zero at absolute zero E) ΔS = qrev/T at constant temperature

Which one of the following processes produces a decrease in the entropy of the system? A) boiling water to form steam B) the dissolution of solid KCl in water C) the mixing of two gases into one container D) freezing water to form ice E) melting ice to form water

ΔS is negative for the reaction___________. A) 2 SO₂ (g) + O₂ (g) → 2 SO₃ (g) B) NH₄Cl (s) → NH₃ (g) + HCl (g) C) PbCl₂ (s) → Pb²⁺ (aq) +2 Cl⁻ (aq) D) 2 C (s) + O₂ (g) → 2 CO₂ (g) E) H₂O (l) → H₂O (g)

Consider a pure crystalline solid that is heated from absolute zero to a temperature above the boiling point of the liquid. Which of the following processes produces the greatest increase in the entropy of a substance? A) melting the solid B) heating the liquid C) heating the gas D) heating the solid E) vaporizing the liquid

For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔH° and ΔS° must be___________and___________, respectively.

If ΔG° for a reaction is greater than zero, then___________. A) K = 0 B) K = 1 C) K > 1 D) K < 1 E) More information is needed

With thermodynamics, one cannot determine___________. A) the speed of a reaction B) the direction of a spontaneous reaction C) the extent of a reaction D) the value of the equilibrium constant E) the temperature at which a reaction will be spontaneous