This practice test covers the key concepts of Unit 6 in AP Chemistry, focusing on thermodynamics and equilibrium. It's designed to help you assess your understanding and identify areas needing further review. Remember to consult your textbook and notes for clarification on any concepts you find challenging.
Section 1: Multiple Choice
(Choose the best answer for each question.)
-
Which of the following is NOT a state function? a) Enthalpy (ΔH) b) Entropy (ΔS) c) Gibbs Free Energy (ΔG) d) Heat (q)
-
A reaction with a negative ΔG is: a) Non-spontaneous b) Spontaneous at high temperatures only c) Spontaneous at low temperatures only d) Spontaneous under all conditions
-
What does a positive ΔS indicate about a system? a) The system is becoming more ordered. b) The system is becoming less ordered. c) The system's temperature is increasing. d) The system's pressure is increasing.
-
The equilibrium constant (K) for a reaction is related to the standard Gibbs Free Energy change (ΔG°) by which equation? a) K = -RTΔG° b) K = e^(-ΔG°/RT) c) K = e^(ΔG°/RT) d) K = RTΔG°
-
According to Le Chatelier's principle, if the pressure is increased on a system at equilibrium, the equilibrium will shift to favor the side with: a) Fewer moles of gas b) More moles of gas c) More moles of liquid d) No change in equilibrium position
-
A buffer solution resists changes in: a) Temperature b) Pressure c) pH d) Volume
-
Which of the following is a strong acid? a) HF b) CH₃COOH c) HCl d) NH₃
-
What is the pH of a 0.1 M solution of a strong acid? a) 0 b) 1 c) 7 d) 13
-
What is the relationship between Kₐ and K𝑏 for a conjugate acid-base pair? a) Kₐ x K𝑏 = 1 b) Kₐ + K𝑏 = 14 c) Kₐ x K𝑏 = Kw d) Kₐ / K𝑏 = Kw
-
Consider the reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). Adding more N₂ to the system at equilibrium will: a) Decrease the concentration of NH₃ b) Increase the concentration of NH₃ c) Have no effect on the concentrations of reactants or products d) Decrease the equilibrium constant
Section 2: Free Response
(Show your work for full credit.)
-
Calculate the ΔG° for a reaction at 298 K with ΔH° = -50 kJ/mol and ΔS° = +100 J/mol·K. Is this reaction spontaneous under standard conditions? Explain.
-
A weak acid, HA, has a Kₐ of 1.0 x 10⁻⁵. Calculate the pH of a 0.10 M solution of HA.
-
Explain Le Chatelier's principle and provide an example of how it applies to a real-world chemical system.
-
Describe how a buffer solution works and explain why it is important in maintaining a stable pH.
-
Explain the difference between Kc and Kp, and how they are related.
This practice test provides a solid foundation for reviewing Unit 6. Remember to consult your notes, textbook, and teacher for further assistance. Good luck!
