AP Chemistry – AP Chemistry – Mistake Review
Mistake Review – Focus on Weak Point
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Do NOT rush
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Say reasoning out loud
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Goal: never miss these again
PART 1: Equilibrium ( #1 Weak Area)
Question 1
If Q < K, the reaction will:
A. shift left
B. shift right
C. stop
D. no change
... Correct Answer: B Why: Q < K means not enough products → reaction moves forward. Common Mistake: Confusing QK. Fix It: Q K → LEFT
Question 2
If Q > K, the reaction will:
A. shift right
B. shift left
C. stop
D. no change
... Correct Answer: B Why: Too many products → system shifts left. Fix It: Too much product → go backward
Question 3
For:
N₂ + 3H₂ ⇌ 2NH₃
If pressure increases:
A. shift left
B. shift right
C. no change
D. depends
... Correct Answer: B Why: Left = 4 moles gas Right = 2 moles gas → shift to fewer moles Fix It: High pressure → fewer gas molecules
Question 4
Removing product causes equilibrium to:
A. shift left
B. shift right
C. no change
D. stop
... Correct Answer: B Why: System tries to replace removed product. Fix It: Remove product → make more product
Question 5
For an exothermic reaction, increasing temperature:
A. shifts right
B. shifts left
C. no change
D. increases K
... Correct Answer: B Why: Heat is product → adding heat shifts left. Fix It: Exo + heat → LEFT Endo + heat → RIGHT
Question 6
Which factor changes K?
A. pressure
B. concentration
C. catalyst
D. temperature
... Correct Answer: D Why: Only temperature changes equilibrium constant. Fix It: Only TEMP affects K
PART 2: Acid–Base Precision (#2)
Question 7
What is 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 8
Which has highest pH?
A. 1 M acid
B. 0.1 M acid
C. 0.01 M acid
D. 0.001 M acid
... Correct Answer: D Why: More dilute → fewer H⁺ → higher pH Fix It: Dilution ↑ → pH ↑
Question 9
Adding acid to a buffer will:
A. big decrease
B. small decrease
C. increase pH
D. no change
... Correct Answer: B Why: Buffer resists change. Common Mistake: Thinking big pH change. Fix It: Buffer = small change only
Question 10
Diluting an acid:
A. lowers pH
B. raises pH
C. no change
D. neutralizes
... Correct Answer: B Why: [H⁺] decreases → pH increases Fix It: Dilution = less acidic
FINAL 10 QUESTIONS (AP 5-Level Training)
Question 11(Q vs K Trap)
For a reaction, Q = 0.5 and K = 5. What happens?
A. shift left
B. shift right
C. no change
D. stop
... Correct Answer: B Why: Q < K → not enough product → shift right. Trap: Students reverse Q and K. Fix It: Q K → LEFT
Question 12(Exo vs Endo Trap)
For an exothermic reaction, increasing temperature:
A. increases K
B. decreases K
C. no change
D. shifts right
... Correct Answer: B Why: Heat is product → adding heat shifts left → less product → K decreases. Trap: Students think temp always increases K. Fix It: Exo → temp ↑ → K ↓ Endo → temp ↑ → K ↑
Question 13(Pressure + Moles)
If pressure increases, equilibrium shifts toward:
A. more gas moles
B. fewer gas moles
C. solids
D. liquids
... Correct Answer: B Why: System reduces pressure by lowering gas particles. Trap: Forgetting to COUNT moles. Fix It: Pressure ↑ → fewer moles
Question 14(Catalyst Trap)
Adding a catalyst will:
A. increase K
B. shift equilibrium
C. speed reaction
D. increase products
... Correct Answer: C Why: Catalyst lowers activation energy only. Trap: Thinking equilibrium shifts. Fix It: Catalyst = faster ONLY
Question 15(K Expression Trap)
Which is included in K?
A. solids
B. liquids
C. gases
D. none
... Correct Answer: C Why: Only (g) and (aq) included. Trap: Students include everything. Fix It: Ignore solids & liquids
Question 16(pH Quick Calculation)
What is pH of 1×10⁻⁶ M HCl?
A. 4
B. 5
C. 6
D. 7
... Correct Answer: C Why: pH = -log(10⁻⁶) = 6 Trap: Overthinking log. Fix It: Exponent = pH
Question 17(pH vs Strength Trap)
Which is MOST acidic?
A. 0.1 M HCl
B. 0.01 M HCl
C. 0.001 M HCl
D. 1 M HCl
... Correct Answer: D Why: Highest concentration → most H⁺ → lowest pH. Trap: Confusing dilution. Fix It: More concentrated → more acidic
Question 18(Buffer Trap)
A buffer resists pH change because:
A. it is neutral
B. it reacts with added acid/base
C. it has high pH
D. it stops reactions
... Correct Answer: B Why: Buffer components neutralize added acid/base. Trap: Thinking buffer = neutral. Fix It: Buffer = reacts to stabilize
Question 19(Dilution Trap)
Diluting a base will:
A. increase pH
B. decrease pH
C. no change
D. neutralize
... Correct Answer: B Why: [OH⁻] decreases → pH decreases. Trap: Mixing acid/base logic. Fix It: Dilute base → less basic
Question 20(Equilibrium Concept)
At equilibrium:
A. reaction stops
B. forward = reverse rate
C. equal concentrations
D. no movement
... Correct Answer: B Why: Dynamic equilibrium → reactions still occur. Trap: Thinking reaction stops. Fix It: Rates equal, not amounts
PART 3: FRQ Precision (CRITICAL FOR 5)
FRQ 1
Explain effect of catalyst
... Perfect Answer: A catalyst lowers activation energy, increasing the rate of both forward and reverse reactions equally. It does not change the equilibrium constant or equilibrium position.
FRQ 2
Explain equilibrium shift with temperature (endothermic)
... Perfect Answer: In an endothermic reaction, heat acts as a reactant. Increasing temperature adds heat, shifting equilibrium to the right to produce more products.
FRQ 3
Explain dilution effect
... Perfect Answer: Dilution decreases the concentration of H⁺ ions, which increases the pH of the solution.