CPC CPC Physical Chemistry & Thermodynamics

Question 1

According to the first law of thermodynamics, which statement is correct?

Accepted Answer

The total energy of an isolated system is constant

Answer

The first law states that energy is conserved: ΔU = q + w, meaning the internal energy change equals the heat added plus the work done on the system.

Question 2

The Gibbs free energy change (ΔG) at standard conditions for a spontaneous reaction must be:

Accepted Answer

Negative

Answer

A spontaneous process at constant temperature and pressure has ΔG < 0, indicating the system releases usable free energy.

Question 3

The van't Hoff equation relates the equilibrium constant K to temperature through which thermodynamic quantity?

Accepted Answer

ΔH°

Answer

The van't Hoff equation, d(ln K)/dT = ΔH°/RT², shows how K changes with temperature based on the standard enthalpy of reaction.

Question 4

Which colligative property is used to determine the molar mass of a large polymer in solution?

Accepted Answer

Osmotic pressure

Answer

Osmotic pressure (π = MRT) is the most sensitive colligative property for large molecules because it produces measurable pressures even at very low molar concentrations.

Question 5

In the Arrhenius equation k = A·e^(−Ea/RT), increasing the temperature primarily affects the reaction rate by:

Accepted Answer

Increasing the fraction of molecules with sufficient energy to react

Answer

Higher temperature increases the Boltzmann factor e^(−Ea/RT), meaning a larger fraction of molecules have kinetic energy exceeding the activation energy Ea.

(CPC) Certified Professional Chemist Practice Test

(CPC) Certified Professional Chemist Practice Test

CPC CPC Physical Chemistry & Thermodynamics