ACS CP Thermodynamics & Chemical Kinetics

Question 1

For a reaction at standard conditions with ΔG° = -20.0 kJ/mol at 298 K, what is the equilibrium constant K? (R = 8.314 J/mol·K)

Accepted Answer

K ≈ 2,960

Answer

Using ΔG° = -RT ln K, K = e^(-ΔG°/RT) = e^(20000/2478) ≈ 2,960.

Question 2

Which thermodynamic state function represents the maximum non-expansion work obtainable from a process at constant temperature and pressure?

Accepted Answer

Gibbs free energy (G)

Answer

Gibbs free energy (G) represents the maximum non-expansion work available from a system at constant T and P.

Question 3

According to Hess's Law, the standard enthalpy change of a reaction is:

Accepted Answer

Independent of the pathway taken

Answer

Hess's Law states that enthalpy is a state function, so the total ΔH is independent of the reaction pathway.

Question 4

For an ideal gas expanding isothermally and reversibly, which relationship correctly applies the First Law of Thermodynamics?

Accepted Answer

q = -w and ΔU = 0

Answer

For an ideal gas at constant temperature, ΔU = 0; applying the first law (ΔU = q + w) gives q = -w.

Question 5

The Clausius-Clapeyron equation is primarily used to relate which two properties during phase transitions?

Accepted Answer

Vapor pressure and temperature

Answer

The Clausius-Clapeyron equation d(ln P)/dT = ΔHvap/RT² relates vapor pressure to temperature during phase transitions.

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