Chemistry Test Physical Chemistry 2 — Questions and Answers
Question 1: Which thermodynamic quantity remains constant in an adiabatic process?
- Entropy
- Temperature
- Heat (q = 0) (Correct answer)
- Pressure
Correct answer: Heat (q = 0)
An adiabatic process is defined by zero heat exchange between the system and surroundings (q = 0).
Question 2: The van't Hoff factor (i) for a strong electrolyte like NaCl dissolved in water is approximately:
- 1
- 2 (Correct answer)
- 0.5
- 3
Correct answer: 2
NaCl fully dissociates into Na⁺ and Cl⁻, giving two particles per formula unit, so i ≈ 2.
Question 3: According to the Arrhenius equation, plotting ln(k) vs 1/T yields a slope of:
- -Ea/R (Correct answer)
- Ea/R
- -R/Ea
- Ea·R
Correct answer: -Ea/R
The Arrhenius equation ln(k) = ln(A) − Ea/R · (1/T) shows the slope equals −Ea/R.
Question 4: What does a negative value of ΔG indicate about a chemical reaction?
- The reaction is non-spontaneous
- The reaction is spontaneous (Correct answer)
- The reaction is at equilibrium
- The reaction absorbs heat
Correct answer: The reaction is spontaneous
A negative Gibbs free energy change (ΔG < 0) indicates the reaction proceeds spontaneously under constant temperature and pressure.
Question 5: Which colligative property is used to determine the molar mass of a polymer dissolved in solution?
- Boiling point elevation
- Freezing point depression
- Osmotic pressure (Correct answer)
- Vapor pressure lowering
Correct answer: Osmotic pressure
Osmotic pressure is preferred for high-molar-mass polymers because it produces measurable pressure differences even at very low concentrations.
Question 6: In a reaction where the order is zero with respect to a reactant, the rate:
- Doubles when that reactant's concentration doubles
- Is unaffected by that reactant's concentration (Correct answer)
- Halves when that reactant's concentration doubles
- Is proportional to the square of the concentration
Correct answer: Is unaffected by that reactant's concentration
A zero-order dependence means the rate expression contains [A]⁰ = 1, so concentration changes have no effect on rate.
Question 7: The Debye-Hückel limiting law applies to solutions that are:
- Concentrated strong electrolytes
- Dilute strong electrolytes (Correct answer)
- Concentrated weak acids
- Non-electrolyte mixtures
Correct answer: Dilute strong electrolytes
The Debye-Hückel limiting law accurately describes activity coefficients only in dilute strong electrolyte solutions.
Chemistry Test Physical Chemistry 2
Which thermodynamic quantity remains constant in an adiabatic process?