AP Chemistry – Mock Test 2
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Time yourself: 20 minutes
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No checking answers until finished
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Focus on reasoning, not memorization
SECTION 1: MCQ
Question 1
Which element has the highest ionization energy?
A. Na
B. Mg
C. Al
D. Cl
... Correct Answer: D Why: Ionization energy increases across a period (left → right). Common Mistake: Thinking larger atoms have higher ionization energy. Fix It: Smaller atom = harder to remove electron
Question 2
Which molecule has trigonal planar geometry?
A. CH₄
B. NH₃
C. BF₃
D. H₂O
... Correct Answer: C Why: BF₃ has 3 bonding pairs and no lone pairs → trigonal planar. Fix It: 3 regions = trigonal planar
Question 3
Which has strongest intermolecular forces?
A. CO₂
B. CH₄
C. NH₃
D. H₂
... Correct Answer: C Why: NH₃ forms hydrogen bonds. Fix It: H–N, H–O, H–F → hydrogen bonding
Question 4
For the reaction at equilibrium:
If Q > K, the reaction will:
A. shift right
B. shift left
C. stay same
D. stop
... Correct Answer: B Why: Too many products → system shifts left. Fix It: Q > K → go backward
Question 5
Which change increases reaction rate?
A. lower temperature
B. add catalyst
C. decrease concentration
D. remove reactants
... Correct Answer: B Why: Catalyst lowers activation energy. Fix It: Catalyst = faster reaction
Question 6
What is the pH of 1×10⁻⁵ M HCl?
A. 3
B. 4
C. 5
D. 6
... Correct Answer: C Why: pH = -log(10⁻⁵) = 5 Fix It: Exponent = pH
Question 7
Which process is endothermic?
A. freezing
B. condensation
C. evaporation
D. deposition
... Correct Answer: C Why: Evaporation absorbs heat. Fix It: Liquid → gas = endothermic
Question 8
Increasing pressure shifts equilibrium toward:
A. more moles gas
B. fewer moles gas
C. liquids
D. solids
... Correct Answer: B Why: System reduces pressure by decreasing gas moles. Fix It: High pressure → fewer moles
Question 9
Which species is oxidized?
Zn → Zn²⁺ + 2e⁻
A. Zn
B. Zn²⁺
C. e⁻
D. none
... Correct Answer: A Why: Oxidation = loss of electrons. Fix It: LEO (Lose Electrons = Oxidation)
Question 10
Which solution is most basic?
A. pH 3
B. pH 5
C. pH 7
D. pH 12
... Correct Answer: D Why: Higher pH = more basic. Fix It: pH ↑ → basic ↑
SECTION 2: FRQ
FRQ 1
Explain how a catalyst affects a reaction and why it does not change equilibrium position.
... Key Points: - lowers activation energy - speeds forward & reverse - does not change K Sample Answer: A catalyst lowers activation energy, increasing the rate of both forward and reverse reactions equally. It does not change the equilibrium constant, so equilibrium position remains unchanged.
FRQ 2
Explain how concentration changes affect equilibrium.
... Key Points: - system shifts to oppose change - Le Châtelier principle - restore equilibrium Sample Answer: When concentration changes, the system shifts to counteract the change. Increasing reactants shifts equilibrium toward products, while decreasing reactants shifts it toward reactants.