Chemical Thermodynamics Questions

25 Practice QuestionsStart Practicing Now

[Hard]The standard Gibbs free energy change (ΔG°) for a reaction at 298 K is −5.70 kJ mol⁻¹. The equilibrium constant K for this reaction at the same temper...
[Easy]For which of the following reactions is the entropy change (ΔS) expected to be most positive?...
[Hard]Two moles of an ideal gas undergo a reversible isothermal expansion at 27 °C from a volume of 10 L to 100 L. The work done by the gas is approximately...
[Hard]The standard enthalpies of formation of CO₂(g) and H₂O(l) are −393.5 kJ mol⁻¹ and −285.8 kJ mol⁻¹ respectively. If the standard enthalpy of combustion...
[Easy]The standard enthalpy of combustion of methane is −890 kJ mol⁻¹. If 4.0 g of methane (CH₄, molar mass = 16 g mol⁻¹) is burned completely, the heat rel...
[Medium]Given: C(s) + O₂(g) → CO₂(g); ΔH = −393 kJ mol⁻¹ CO(g) + ½O₂(g) → CO₂(g); ΔH = −283 kJ mol⁻¹ The enthalpy of formation of CO(g) from its element...
[Medium]The bond enthalpies of H–H, Cl–Cl, and H–Cl bonds are 436, 242, and 431 kJ mol⁻¹ respectively. The enthalpy change for the reaction H₂(g) + Cl₂(g) → 2...
[Easy]A gas absorbs 120 J of heat and expands against a constant external pressure, performing 50 J of work on the surroundings. The change in internal ener...
[Medium]Melting of ice at 273 K and 1 atm is a spontaneous process. Which of the following correctly describes the thermodynamic parameters at the melting poi...
[Medium]For a certain reaction at 300 K, ΔH = −15 kJ mol⁻¹ and ΔS = −40 J K⁻¹ mol⁻¹. The Gibbs free energy change (ΔG) and the spontaneity of the reaction at ...
[Easy]At constant T and P, spontaneity criterion is:...
[Medium]In a coffee-cup calorimeter, dissolution of 5.00 g KCl (ΔHsol = +17.2 kJ mol⁻¹) in 100.0 g water causes temperature drop. Molar mass KCl ≈ 74.5 g mol⁻...
[Medium]For reversible isothermal expansion of an ideal gas, work done is maximum because:...
[Hard]Estimate ΔH (kJ mol⁻¹) for CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) using average bond enthalpies. (Data approximate: C–H: 413, O=O: 498, C=O in CO2: 799, O...
[Easy]Third Law of Thermodynamics states entropy of a perfect crystal at 0 K is:...
[Medium]A non-spontaneous reaction can proceed if coupled with a more exergonic one because total ΔG:...
[Medium]A 50.0 g sample of water is heated from 25.0°C to 45.0°C. (Specific heat of water = 4.18 J g⁻¹ K⁻¹). Heat absorbed (q) is:...
[Hard]For a reaction at 298 K, ΔG° = -9.9 kJ mol⁻¹. The equilibrium constant K is approximately (R = 8.314 J mol⁻¹ K⁻¹):...
[Easy]Which process has ΔS > 0 at constant temperature?...
[Easy]For the reaction: 2C(graphite) + O2(g) → 2CO(g), ΔH = -221 kJ. What is the enthalpy change (ΔH) per mole of CO formed?...
[Easy]Which change is typically endothermic?...
[Easy]ΔH°f of elements in their most stable form at 298 K is:...
[Medium]At 298 K, a reaction has ΔH = +25 kJ mol⁻¹ and ΔS = +120 J mol⁻¹ K⁻¹. Is the reaction spontaneous at 298 K?...
[Easy]Which statement best describes Hess's Law?...
[Medium]Which statement correctly expresses the Second Law of Thermodynamics?...