Exam 19: Chemical Thermodynamics

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 the substance?

Consider the reaction: FeO (s) + Fe (s) + O₂(g) → Fe₂O₃ (s) Given the following table of thermodynamic data at 298 K: The value K for the reaction at 25 °C is ________.

The entropy of a pure crystalline substance at 0 °C is zero.

The normal boiling point of ethanol (C₂H₅OH)is 78.3 °C and its molar enthalpy of vaporization is 38.56 kJ/mol. What is the change in entropy in the system in J/K when 112.2 grams of ethanol at 1 atm condenses to a liquid at the normal boiling point?

ΔS is positive for the reaction ________.

Which reaction produces a decrease in the entropy of the system?

The second law of thermodynamics states that ________.

Given the following table of thermodynamic data, complete the following sentence. The vaporization of TiCl₄ is ________.

Use the table below to answer the questions that follow. Thermodynamic Quantities for Selected Substances at 298.15 K (25 °C) Substance ΔH°_f (kJ/mol)ΔG°_f (kJ/mol)S (J/K-mol) Calcium Ca (s)0 0 41.4 CaCl₂ (s)-795.8 -748.1 104.6 Ca₂⁺ (aq)226.7 209.2 200.8 Chlorine Cl₂ (g) 0 0 222.96 Cl- (aq)-167.2 -131.2 56.5 Oxygen O₂ (g)0 0 205.0 H₂O (l)-285.83 -237.13 69.91 Phosphorus P₂ (g)144.3 103.7 218.1 PCl₃ (g)-288.1 -269.6 311.7 POCl₃ (g)-542.2 -502.5 325 Sulfur S (s, rhombic)0 0 31.88 SO₂(g)-269.9 -300.4 248.5 SO₃(g)-395.2 -370.4 256.2 -The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, 2S (s, rhombic) + 3O₂(g) → 2SO₃ (g) Is ________ J/K ^∙ mol.

Of the following, the entropy of ________ is the largest.

The value of ΔG° at 25 °C for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen, SO₂ (g) → S (s, rhombic) + O₂ (g) Is ________ kJ/mol.

The value of ΔS° for the decomposition of calcium chloride into its constituent elements, CaCl₂ (s) → Ca (s) + Cl₂ (g) Is ________ J/K ∙ mol.

For a given reaction, ΔS = +69.0 J/mol∙K, and the reaction is spontaneous at temperatures above the crossover temperature, 439 K. The value of ΔH = ________ kJ/mol , assuming that ΔH and ΔS do not vary with temperature.

The value of ΔH° for the decomposition of phosphorous trichloride into its constituent elements, 2PCl₃ (g) → P₂ (g) + 3Cl₂ (g) Is ________ kJ/mol.

With thermodynamics, one cannot determine ________.

Use the table below to answer the questions that follow. Thermodynamic Quantities for Selected Substances at 298.15 K (25 °C) Substance ΔH°f (kJ/mol)ΔG°f (kJ/mol)S (J/K-mol) Carbon C (s, diamond)1.88 2.84 2.43 C (s, graphite)0 0 5.69 C₂H₂ (g)226.7 209.2 200.8 C₂H₄ (g)52.30 68.11 219.4 C₂H₆ (g)-84.68 -32.89 229.5 CO (g)-110.5 -137.2 197.9 CO₂ (g)-393.5 -394.4 213.6 Hydrogen H₂( g)0 0 130.58 Oxygen O₂ (g)0 0 205.0 H₂O (l)-285.83 -237.13 69.91 -The value of ΔS° for the catalytic hydrogenation of acetylene to ethane, C₂H₂ (g) + 2H₂ (g) → C₂H₆ (g) Is ________ J/K ∙ mol.

The vaporization of a substance at its boiling point is an isothermal process.

The melting of a substance at its melting point is an isothermal process.

For an isothermal process, the entropy change of the surroundings is given by the equation:

The value of ΔH° for the formation of calcium chloride from its constituent elements, Ca (s) + Cl₂ (g) → CaCl₂ (s) Is ________ kJ/mol.